Halftone colour image signal processing apparatus

Abstract: An original colour image (52) is scanned and the image signal is decomposed into two colour components (R,Cy) by a dichromic mirror (55). Each colour component undergoes A/D conversion (60,61) and shading correction (15A,15B). Then a colour discrimination circuit (35) gives each pixel a 2-bit colour code denoting either red, cyan or black, and a 6-bit density code. Based on thus obtained digital image data, colour image processing is performed which includes colour ghost correction (300), MIF correction (450), and partial colour conversion (500) which changes the colour of a region specified by a contour of a particular colour. Finally a binary circuit (600B) together with a threshold selector (600A) outputs a binary code which is sent to an output device (700) via an interface (40).

Description: This invention generally relates to a color image processing apparatus for processing color image signal, and specially relates to a color image processing apparatus applicable to a simple electrophotographic color copying machine in order to obtain satisfactory color image. The color image processing apparatus optically reads color image information on a document, identifies the information as one of predetermined multiple colors including black, red and blue, and record a color image on a record sheet on the basis of the information by using a color recording device. This type of color image processing apparatus is disclosed in Japanes Patent Publication Nos. JP-A-57 147 374 (1982) and JP-A-58 062 769 (1983). Fig. 76 shows part of a key assembly of the said color image processing apparatus. In this figure, color image information is separated into white and cyan colors, each of which is projected onto image sensors 104 and 105 for electrophotographic conversion. More specifically, white and cyan color signals are supplied to the subtracter 2 where red color is separated. These white, cyan and red colors are gain-controlled by the AGC circuits 3, 4 and 5, respectively, and then are coded by the binary coding circuits 6, 7 and 8, respectively. The coded output is again converted into red and black color signals by the arithmetic circuit 9, for example, and these signals are supplied to the color copying machine as image signals for color reproduction of the original. With a color image processing apparatus capable of recording such a color image, when subjecting an image signal undergone photoelectric conversion to various processing such as resolution correction, and enlarging/reducing, it is necessary to provide processing means per color identified by color separation means or color discrimination means. More specifically, as shown in Figs. 77 and 78, one image processing circuit is required per color signal, disadvantageously resulting in increased cost, as well as a large processing circuit. Japanese Patent Publication No. JP-A-59 163 980 (1984) described a technique for representing the image signal reading using color codes. This patent, however, merely describes a technique for converting an image signal into color codes, and discloses nothing about an effective image processing based on color codes. Additionally, this technique incurs another problem: the image signal does not contain data indicating image density, and density processing is impossible. There is another color image processing technique where a specific region on a document designated with a marker of a specific color is detected, and the so-detected are is subjected to a specific image processing operation. For example, as shown in Fig. 79, once a portion of a black-and-white document is marked with a colorant of a specific color (for example, red), the image information on inside the color-marked region is recorded as converted from black into red that is a color of the marker. Japanese Patent Publication Nos. JP-A-57 089 371 (1982) and JP-A-57 196 658 (1982) disclose apparatuses that are capable of detecting a marker-designated region. These apparatuses discriminates and read a color different from that of a document, and photoelectrically convert it to generate an image signal, thereby based on the image signal, the apparatuses detect a region defined by a color marker. These apparatuses can discriminate and read a region that has a color different from that of a document, wherein the apparatuses feed an image signal based on the so-separated information, and detect a marker-designated region. Fig. 80 presents an example of the configuration of an image pickup unit for the image processing apparatus. According to the configuration, the manuscript or document 2 on the platen glass 1 is scanned by the exposure light source 5 installed on the carriage travelling on the slide rail 3. The reflection from the manuscript 2 is guided to the lens 10 through the mirror 6 fixed on the carriage 4 and the mirrors 8 and 9 fixed to the moving mirror unit 7 to form the image on the CCD image sensor 12 on the circuit board. Numeral 13 shows a standard white board installed on the rear side of the edge of the platen glass 1 in the exposure scan direction, and provides the standard white signal at the start of manuscript reading. With the stepping motor (not illustrated), the wire 15, and the pulleys 16 to 19, the moving mirror unit travels at a speed twice that of the carriage 4. The light path from the document 2 to the CCD image sensor 12 is kept constant in exposure scanning. The exposure light 5 uses a green, commercially available fluorescent light in order to prevent white color emphasis and attenuation based on the light source. To prevent the fluorescent light from flickering, a 40 kHz high-frequency light source is used to turn on the light. Furthermore, a heater is used to keep the tube wall temperature constant and to achieve quick warming. Beside mechanical causes of poor picture quality, the image reader or copying machine using the pickup system with a CCD image sensor provides some other causes including light-emitting spectrum distribution of the light source, mirror flatness, mirror vibration during its movement, modulation transfer function (MTF) of the mirror system and light-receiving sensitivity of the sensor. With respect to the color image pickup, there are other causes for poor picture quality including dichroic mirror transparent reflection characteristic and flatness/parallelism of the prism surface. MTF design of the mirror system is the most important for improved resolution. The MTF of the signal from the CCD image sensor depends on these causes. Comparison of poor MTF (due to distorted signal as shown Fig. 81 (a)) and better MTF as shown in Fig. 81 (b) demonstrates totally different reproduction of fine parts of image when image signal is coded with threshold (I) or (II). This indicates that correcting MTF for improved resolution is essential for reproduction of fine lines or characters. There are two main methods to improve resolution for higher image quality: (1) a method to apply some measure in the time of coding picture signals and (2) a method to correct picture signals digitally. The method (1) is illustrated in Fig. 82 (a). This method uses a low-pass filter to catch a variation in average value of the picture signal in digitizing the signal. This variation is used for a reference for determining a threshold in the digitization. This method allows the threshold to be floated and catch up typical variations of picture signal, resulting in better picture quality. The logic expansion of this method is known as an SWCC method. As shown in Fig. 82 (b), the SWCC method makes a comparison signal by shifting the phase of picture signal to obtain digitized (binary) signal by making comparison with the comparison signal. This method applies to analog signal processing; in fact, it is applicable to the case where shading correction is not required as a high-accuracy correction means, especially to the system which install a light shutoff board in front of lens or to the system which provides few noises. However, the method cannot be applicable to the system which call for stability for temperature or good reproduction of picture or color image. Method (2) is typically known as a differential operator which is described below. In the case where taking a 2 by 2 pixel array like; In the case where taking a 3 by 3 pixel array like; This method performs each calculation of (1) to (14), with a to d, and A to I being picture data. Formula (13) corresponds to a two-dimensional Laplacian calculation. Examples of this method with the calculation are disclosed in Japanese Patent Publication Nos. JP-A-53 043 529 (1978) and JP-A-56 042 870 (1981). However, when applied to the system which uses a CCD image sensor to pick up images, these examples are not so effective with respect to the direction orthogonal to the linearly-arranged direction of a CCD image sensor pixel array. One of the causes lies in the system shown in Fig. 80 using a charge-storing CCD image sensor for image pickup which provides a wider region in the secondary scan direction than in the primary scan direction, as shown in Figs. 83 and 84. In addition, the aperture of the image sensor is apt to be longer than that in the primary scan direction, making effective resolution lower and inevitably ensuring MTF with respect only to a single cross section due to restrictions of lens treatment and yield. This makes the direction with a good MTF coincident with the primary scan direction, resulting in lower lens MTF in the direction of secondary scan than that in the direction of primary scan. Accordingly, conventional MTF correction with corrected coefficients provides satisfactory result in the direction of the primary scan, but unsatisfactory result in the direction of secondary scan, or excessive correction in the direction of the primary scan. This emphasizes noises and the uneven surface of paper used, leading in conspicuous isolated noises. Fig 85 (a) to (c) give an example of comparison of three cases in picture signal level. An appropriate threshold value for multivalue coding an image signal undergone image processing has been hitherto been determined by generating a histogram by prescanning, or by determining a density range of the image and by multiplying the range by a predetermined factor. However, the former technique requires a duration for both prescanning and histogram generation, and to a disadvantage, results in a larger circuit configuration; the latter technique, though not requiring prescanning for histogram generation, fails to determine satisfactorily reasonable threshold values solely based on data resultant from the density range. As shown in Figs. 77 and 78, based solely on a color of a specific document, the result signal is unconditionally a single type of signal. Correspondingly, the gamma correction on a document image being read requires an image processing circuit for gamma correction, and, this means necessity of an arithmetic operation for every data set. The document US-A-4538182 (or equivalent FR-A-2505518) describes an image processing apparatus for detecting a region marked with a color on a document, the color being a different color from colors of an original image on said document; said apparatus comprising: means for obtaining a color image signal having a plurality of color component signals in respect of each pixel by reading said document; color discriminating means; and region detecting means. The present invention is characterized in that: said color discriminating means operates to convert said color image signal into first and second signal portions in respect of each said pixel, the first signal portion being a multiple bit density data signal common to said plurality of color component signals and representative of the original image density of that pixel, and the second signal portion being one of a plurality of predetermined color code data signals, said color discriminating means operating to classify all the color information read from said original document by said obtaining means into one of said predetermined color code data signals each representative of one of a plurality of predetermined mutually different colors; said region detecting means is adapted to detect said region by detecting said different color based on said color code data signal; and output means responsive to the multiple bit density data signal and the color code data signals to provide signals for reproducing the processed image in desired colors and density. The above-mentioned US-A-4538182 converts the color image signal into color identification signals, not into first and second signal portions of different types, one identifying color and the other providing density data, in respect of each said pixel. The present invention thus permits control of individual color toner density in the eventually reproduced processed image. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 shows a block diagram of an overall color image processing apparatus of the invention which is used for the brief description. Fig. 2 is a configuration of a key part of a color copying machine applicable to the invention. Fig. 3 presents characteristics of dichroic mirror permeability, and Fig. 4, relative spectrum of the light source. Fig. 5 illustrates a spectral characteristic of CCD, and Fig. 6, relative luminance distribution. Fig. 7 is a descriptive drawing for shading correction. Fig. 8 presents a shading correction circuit diagram. Figs. 9 and 11 are waveforms for shading correction. Fig. 10 is a configuration of the analog/digital converter, and Fig. 12, its descriptive drawing. Both Figs. 13 and 14 illustrate typical color separation maps. Figs. 15 and 17 are block diagrams showing embodiments of color separation circuits and Fig. 16 is a descriptive diagram for a γ-correction curve. Figs. 18 and 19 are descriptive illustrations for color ghost. Likewise, Figs. 20, 21 and 25 explain and illustrate color ghost generation. Fig. 22 is a configuration of a CCD mounting apparatus; Fig. 23, the configuration of its key part; and Fig. 24, a cross-section of part of the apparatus. Figs. 26 and 27 present descriptive drawings for color ghost correction. Fig. 28 is a color ghost correction circuit diagram, and both Figs. 29 and 30, characteristic drawings used for its explanation. Fig. 31 is a block diagram for the resolution correction means. Figs. 32 and 33 present descriptive illustrations for partial color conversion. Figs. 34 and 35 are descriptive illustration for partial color conversion. Figs. 36, 37 and 38 show block diagram for the region extracting circuit, marker detecting circuit, and region extracting assembly, respectively. Fig. 39 is a waveform used for description of the region extracting assembly's operation. Fig. 40 shows a block diagram for region determining circuit. Figs. 41, 42, 43 and 55 are all present illustrations that explain the region determining circuit. Fig. 44 is a block diagram for data selecting circuit. Fig. 45 is a block diagram showing another embodiment of the color image processing apparatus according to the invention, Fig. 46 is a block diagram showing the region determinating circuit being incorporated in a color code converting part, Fig. 47 is a table indicating the relation between color and code data, Fig. 48 is a descriptive diagram for color code conversion, Fig. 49 is a block diagram showing a data selection circuit, Fig. 50 is a table indicating a relation between output signal and BBR signal, Fig. 51 is a descriptive diagram indicating one example of data selection, Fig. 52 is a flow chart of copy mode, Figs. 53 and 54 are descriptive illustration for the flow chart of Fig. 52. Fig. 56, density histogram characteristics. In Figs. 57 to 59, block diagrams for the automatic threshold determining means are presented. In Fig. 60, another example of color separation map. Figs. 61 and 62 are a block diagram for the overall of the interface and its first interface, while Fig. 63, a waveform that describes the interface operation. Figs. 64 and 65 present a block diagram for the output apparatus and the laser beam scanner, respectively. Fig. 66 is a cross section of developing apparatus. Fig. 67 presents a descriptive drawing for developing process. Figs. 67 and 68 are a block diagram for the second controller and the first controller, respectively. In Figs. 70, 71 and 72 there are waveforms that explain operations of the controller. Fig. 73 is an illustration for index sensor description. Fig. 73 shows a key layout for the operation/indicator panel, while Fig. 75 gives key operation description. Figs. 76, 77, and 78 are block diagrams used for describing conventional units. Fig. 79 is a descriptive illustration for recording with a partial color conversion. Fig. 80 presents a mechanism of a pickup unit using a CCD image sensor. Fig. 81 (a) and (b) are description drawings which show difference of signals after having been digitized which is attributable to differences in resolution. Fig. 82 (a) and (b) describe how to set thresholds to improve resolution. Figs. 83 and 84 describe pickup scan with a CCD image sensor, and Fig. 85 (a) to (c) give descriptions for resolution correction. DETAILED DESCRIPTION OF THE INVENTION An example of the color image processing apparatus related to the invention is explained, using these figures. The configuration of the color image processing apparatus is presented in Fig. 1. The color image information (optical image) on the document 52 is separated into two color separation images by the dichroic mirror 55. In this example, color image information is separated into red R and cyan Cy color separation images. This color separation is conducted by use of the dichroic mirror 55 having cut off range of 540 to 600 mm. This enable the red component to form a transmitted light, and the cyan component to form reflected light. Red R and cyan Cy color separation images are supplied to such image reading units as CCDs 104 and 105 through which image signals of red component R and cyan component Cy are provided. Image signals R and Cy are supplied to analog/digital converters 60 and 61 where they are converted into digital signals with the predetermined bits, 6 bits in this example. At the time, shading correction is conducted. 15A and 15B show shading correcting circuits. A detailed description of correction is given later. In gate circuits 30 and 31, digital image signals subjected to the shading correction within maximum document size are extracted; they are supplied to the color discrimination circuit 35 of next stage. For documents of B4 size, the size signal B4 produced by the system timing signal forming means (not illustrated) is used as a gate signal. Assuming that shaded digital image signals are VR and VC, VR and VC are supplied into the color separating circuit or color discriminating circuit 35 where they are discriminated as one of multiple color signals. This example shows a configuration to discriminate the image signal as one of color signals: red, blue and black. Namely, possible colors of original images on a document are respectively discriminated per pixel as one of predetermined colors such as red, blue or black. Through this discriminating operation, the document is deemed to consist of images whose color is one of red, blue or black colors. In this example, the above predetermined colors are determined as red, blue and black color on the basis of recording colors of a recording apparatus, however, it is possible to use other colors. Each discriminated color signal consists of color code data (2-bit data) and density data (6-bit data). As the data of each color signal, one stored in the color discrimination map constituted by a ROM, for example, is used. Color discriminated image data is transferred to the color image processing step. First, the image data is supplied to the color ghost correction means 300 of the next stage where color ghost correction is conducted in the primary (horizontal) scanning direction and in the secondary scanning (drum revolution) direction. 300A shows the color ghost correcting circuit in the primary scanning direction, while 300B shows one in the secondary scanning direction. This color ghost correction is made to prevent undesirable color ghost around letters in black during color separation (color discrimination). Some color separation map (color discrimination map) configurations produce red color around a black letter and blue color at its edge. The picture quality is improved by removing the color ghost. Other image processing includes resolution correction, partial color conversion, and threshold correction for multivaluing, which are shown. These processings (beside enlargement and reduction) are described with specific examples. 450 shows the resolution correction means. This correction means conducts contour correction for density data. The next example is partial conversion. Partial conversion means 500 consists of a region extracting circuit 500A to detect the original picture region marked by color marker on the document, and a color data selecting circuit 500B to copy the extracted region with the color of the color marker. Of course, it is possible to print the region being out of marking line with specified colors. The region extracting circuit 500A provides the region signal that indicates a region enclosed by color marker, as one example. This signal and color code data are supplied to the color data selecting circuit 500B. To the color data selecting circuit 500B, both a signal to indicate which image processing should be conducted by the indicator/operation panel and a BBR signal to indicate the color in which image is to be taken and printed are supplied. Based on these signals and the input signals, determination is made whether or not resolution-corrected density data should be transmitted to the multivaluing means 600 of next stage. For example, to simply conduct normal copy operation, only image data having the same color as that of the BBR signal is provided and then developed. To perform color conversion for the entire document (i.e. to perform conversion between red and blue), control is performed so that red image data is provided during blue color developing, and that blue image data is provided during red color developing. In conducting partial color conversion, black image information in the region enclosed by a color marker is printed with the color of the color marker. For example, if control is performed so that black image, information in the region enclosed by the red marker is printed in the phase where printing in red color is made, the information in this region can be partially converted for printing. Thus, partial color conversion and color specification process are realized only by use of a developing system in which developing is conducted by revolving the drum for each color and fixing is conducted after the completion of development for the last color. In this case, image pickup is also conducted plural times. Image printing can be made real time by performing image pickup and development plural times. The real-time image printing decreases the size of memory needed for image storage. Image data (density data) from the color data selecting circuit 500B is coded into multivalue by the multivalue coding means 600. The example shows the case where 6-bit density data is converted into 1-bit data (binary data, 1 or 0.) The threshold data (6 bits) used as a standard for binarizing is set by automatically or manually. The threshold value selecting means 600A consists of the threshold selecting means 630 for manual setting and the threshold selecting means 610 for automatic setting. The threshold selecting means 630 has been designed to allow independent decision of threshold for each color. This means provides a manually set threshold upon which density data is binarized. The threshold selecting means 610 consists of an ROM that includes the predetermined threshold. Selection of manual or automatic setting of threshold is conducted by the EE release signal. The automatic setting mode (EE mode) is normally assumed. The BBR signal is also supplied to show in which sequence the developing machine is performing its operation. Image data digitized by the coding circuit 600B is supplied to the output unit 700 through the interface circuit 40. The interface circuit 40 has the first interface and the second interface, either of which is used to receive batch image data to control toner density. The output unit 700 can be a laser printing machine. With the laser printing machine, digitized image is converted into a predetermined optical signal which is then modulated based on digitized data. An electrophotographic color copying machine is used for a developing unit. This example shows 2-component non-contact jumping development along with reversal development which calls for no transfer drum used as conventional color image forming. To reduce the machine size, the working example uses the method in which development of three color (blue, red and black) images on an OPC sensitized material (i.e. drum) for image forming is conducted with three revolutions of the drum and then transfer is made once onto a plain paper for copying. Described below are details of components for the color image processing apparatus of the invention. First, a simple color copying is described using Fig. 2 onwards. The simple color copying machine separates possible colors of images on a document into three colors to print color image. This example presents black BK, red R and blue B as these three colors to be separated into. With the machine turned on, the document reading unit A is driven. The first step is to the document 82 on the document table 81 is optically scanned by the optical system. The optical system consists of the fluorescent lamps 85 and 86, the carriage 84 with the reflecting mirror 87, and movable mirror unit 88 with the V mirrors 89 and 89'. The carriage 84 and the moving unit 88 travel on the slide rail 83 by the stepping motor 90 at the predetermined speeds and in the predetermined directions. The fluorescent lamps 85 and 86 illuminate the document 82 on the mirror 87; the image is then supplied to the optical information conversion unit 100 through the V mirrors 89 and 89'. To prevent optical emphasis and attenuance of a specific color in light scanning of a color document, warm white fluorescent lamps are used for the fluorescent lamps 85 and 86. Furthermore, to allow stable illumination, these fluorescent lamps are turned on or driven by a high-frequency power supply of approximately 40 kHz. These lamps are kept warm by a stabilizer-used heater to ensure a constant temperature of their tube walls or to improve warm-up performance. On the rear side of the left edge of the platen glass 81 there is the standard white plate 97 on which optical scanning is made to normalize the image signal into the equivalent white signal. The optical information conversion unit 100 consists of the lens 101, the prism 102, the dichroic mirror 103, the CCD 104 on which red-color-separated image is projected and the CCD105 on which cyan color-separated image is projected. The optical signals from the optical system are focused by the lens 101; they are then separated by the dichroic mirror of the prism 102 into red-color information and cyan-color information. Each of these color-separated images is formed on each CCD's receiving surface, whereby the image signal is converted into the electric signal. The image signal processed by the signal processing system; each chrominance signal is supplied to the printing unit B. As shown in Fig. 1, the signal system includes not only the analog/digital converting means, but also such signal processing circuits as the color separating means and digitizing means. The printing unit B possesses the deflecting unit 935. The deflecting unit 935 can be a galvanomirror, rotating polygan mirror, or a deflecting unit with a quartz-used optical deflector. Laser beam modulated by chrominance signal is deflected and scanned by the deflecting unit. Upon the start of deflection and scanning, beam scan is detected by the laser index sensor (not illustrated) and beam modulation starts by the first chrominance (blue signal, for example). The modulated beam is so controlled that it scans the image forming unit (i.e. sensitizing drum) 11 with uniform charge. The primary scan by laser beam and secondary scan by the rotating image forming unit 11 form a electrostatic image corresponding to the first chrominance signal on the image forming unit 11. The electrostatic image is developed by the developing unit 123 that contains blue toner. The predetermined bias voltage from the high-voltage source is applied to the developing unit 123. This development forms blue image. Toner is supplied as required according to the directive signal from a CPU (not illustrated) for system control which controls a toner supplying means (not illustrated) The blue toner image rotates with contact of the cleaning blade 127 released. Like the first chrominance signal, electrostatic image is formed based on the second chrominance is signal (red signal, for example). By use of the developing unit 124 accommodating red accommodating, this is developed for form red toner image. Of course, the predetermined bypass voltage is applied from the high-voltage power supply to the developing unit 124. Likewise, electrostatics image is formed based on the third chrominance (black) signal, and black toner image is formed based on chrominance (black) signal. This means a multiple-color toner image has been formed on the image forming unit 11. The above description is related to the forming of 3-color toner image; and of course this is applicable to the forming of 2- or 1-color image. The example of development is a so-called non-contact 2-component jumping development in which each toner is jumped toward the image forming unit 11, with AD/DC bias voltage (from the high-voltage power supply) applied. The predetermined amount of toner is supplied to each of the developing unit 124 and 125 according to the directive signal from the CPU. On the other hand, the recording paper P supplied by the paper feeding unit 141 through the feeding roll 142 and the timing roll 143 is carried onto the image forming unit 11, with its timing unit being in line with the revolution of the image forming unit 11. Then, multi-color toner image is transferred onto the paper by the transferring electrode 130 to which high voltage is applied to the high voltage supply and it is separated by the separating electrode 131. The recording paper P is then carried to the fixing unit 132 for obtaining color image by fixing. After the process of transfer, the image forming unit 11 is cleaned by the cleaning unit 126 for preparations for the next image forming. To facilitate toner collection by the blade 127 of the cleaning unit 126, the predetermined DC voltage is applied to the metallic roll 128 of the blace 127. This metallic roll 128 is arranged on the surface of the image forming unit 11 (not contacting the surface). After cleaning, the blace 127 is released from the contact state. The auxiliary cleaning roller 129 is installed to eliminate unwanted toner left after the release. The roller 129 is revolved and contacts in the direction opposite to the image forming unit 11 to satisfactorily clean and remove unwanted toner. The paper feeding unit 141 is equipped with the sensor 65a from which the detection output is forwarded to the CPU. Fig. 3 shows permeability characteristic of the dichroicmirror, Fig. 4, emission spectrum, and Fig. 5 spectral sensitivity characteristic of the light source. The light source can be a fluorescent lamp of daylight or warm white color, or a halogen lamp. A halogen lamp is used along with an appropriate filter to obtain similar emission spectrum. Shading correction is required because there is some problems in the optical system and the light source and there is need for PRNU (photo response non-uniformity) correction of CCD. The optical system follows the law of COS 4 . The second problem related to the light source is described below. A linear light source such as a fluorescent lamp is used for the light source. But this lamp does not produce uniform amount of light with respect to the longitudinal direction of the tube due to filament used as shown Fig. 6. In addition, the fluorescent lamp will produce black spots on the walls of its edge, with unusual decrease in amount of light. Other light sources than a fluorescent lamp varies amount of light depending on the wall temperature. These problems prevent the production of uniform amount of light. CCD involved in the third problem has a single array of pixels (normally 2,048 to 5,000 pixels). It is almost impossible to obtain identical characteristics of all the pixels. Assumed normally is a PRNU of +/-10% which must be needed corrected. Shading produces only white signal with its output level deteriorated at the periphery of the white document, as shown in Fig. 7A. To perform shading correction, the optical system first operators to scan the white standard board 97 prior to the full-scale scanning to obtain the white signal (Fig. 7B). Use of this signal for a reference signal for analog/digital conversion adjusts quantization steps. In other words, quantization steps becomes smaller at the edge of image and becomes larger at the center of image, as shown in Fig. 7A. As result, implementation of analog/digital conversion while modulating the reference signal allows the analog output signal to have a constant output level, as shown in Fig. 7C, which means that shading distortion has been corrected. Thus, the white signal picked up prior to the full-scale scan is used as a standard signal for shading correction. Fig. 8 shows an example of the shading correcting circuit 15A. This example shows the case where image pickup for the white standard board 97 is conducted with respect to two lines to use this as a reference signal. The first buffer 16 is actively controlled by switch signal VS (Fig. 9B) supplied to the buffer during the period for two lines. As a result, the analog-to-digital-converted white signal is stored in the memory through the first buffer 16. In normal image read mode, the image signal shown in Fig. 9A is output and digitalized by the analog/digital converting unit 60. This mode allows the memory to be in the read mode, and the second buffer 17 is controlled actively. The reference signal (white signal) read from the memory 19 is converted into the analog signal by the digital to analog converting unit 20, and is used a reference signal for the analog to digital converting unit 60. Fig. 10 shows that a parallel-type digital analog converting unit is the analog/digital converting unit 60. The said reference signal is applied to each of the parallel type comparator 61. The analog/digital converting unit 60 has 62 is a reference signal/forming means consisting of multiple bleeder resistors, 63 is an encoder and 64 is a latch circuit. To keep the second buffer 17 active in the operation period only, the switch signal and the OR output OR1 of the image valid signal (Fig. 9E) are supplied through the OR circuit 21. This example shows the case where the third buffer 18 is installed to allow analog/digital conversion with the reference signal at the predetermined level (high level) during the period of horizontal blanking. To keep the third buffer active during the period of horizontal blanding (where the image is not valid), the output OR2 (F in Fig. 9), which has been phase-inverted output OR1 by the inverter 22, is supplied. Since the reference signal for the comparator 61 is modulated with the reference signal shown in G in Fig. G, analog image data is like one shown in Fig. H. If the white signals for all the CCD pixels are stored in the memory 19, PRNU correction can be also performed. Shading correction is done independently for the red channel and cyan channel. For example, if the signal for cyan channel is used for correction by use of the signal for the red channel, there is possibility for larger variation the white signal output of the cyan channel after the correction. Fig. 8 presents an example in which analog/digital conversion is done with the reference signal with the reference level of the predetermined level even during the period of horizontal blanking (HBLK). This example is based on the following reasons. If shading correction data stored in one line memory is applied directly into the reference terminal 62a (Fig. 10) of the analog/digital converting unit 60 for analog to digital conversion during shading correction, especially during the image is valid, the analog/digital converting unit 60's conversion range becomes almost zero, and the input signal has the same potential as the reference signal for shading correction. In addition, the input signal contains the noise N more or less (Fig. 11A). The analog/digital converting unit 60 has almost zero range of conversion since it performs determination successively according to voltage variation of input image signal and reference signal, the result of the determination is either the maximum value (high level) or the minimum value (low level). If output varies in a comparatively short period of time due to noises, the comparator and other components of the analog/digital converting unit is turned on or off frequently, resulting in a large current flowing through the analog/digital converting unit. This variation in current produces a relatively large frequency which is not applicable to the signal waveform, giving a great influence upon the input signal as noise. In addition, since a comparatively large current flows through the supply, there is a small impedance and there is a great possibility for small the power line or grounding line include a larger noise. The noise attributable to the value of the input signal of the analog/digital converting unit and that of the reference signal (Fig. 11B) for shading correction are mixed up into the black level of the input signal, resulting in a large variation of the black level (Fig. C). This example does not allow noise mixture by preventing the range of conversion from being 0 V at least during the period of black level outside the period when the image is valid. The working example uses the full-scale value of the analog/digital converting unit as the voltage level for the period when the image is not valid to prevent the range of conversion from being 0 V and the shaded signal and shading signal from having the same voltage. This way of correction enables analog/digital conversion and shading correction to be done at the same time. This method enables correction if the white input signal accounts for 30 to 40% of the full scale (Fig. 12A). Notice that if the white signal below its limit (for example, generated by decrease in amount of light due to blacking or operation over long period), can be corrected, but the noise is superimposed onto the image signal, which prevents direct use of the image signal (Fig. 12B) The next step is to conduct color separation (multiple-bit image data) by use of red and cyan output signals after shading correction. The following example shows the case of three colors: black, red and blue. A conventional way that uses color separation after digitizing the image signal is not appropriate for a variety of signal processing if the fact is taken into account that color-separated data is a digitized signal. In accordance with the present invention the color separation is performed before that digitizing process. For this purpose, the map as shown in Fig. 13 is provide. The color separation map should consist of an ROM (bipolar ROM). Color codes (red, blue and black) and density information are stored into the addresses given by 6-bit image data VR and VC with half tone level. That is, One image information = Color code + Density information For example, a pixel with 30 levels of density in hex (XX011110) provides: Blue = 0 1 0 1 1 1 1 0 = 5E Black = 0 0 0 1 1 1 1 0 = 1E White = 1 1 0 1 1 1 1 0 = DE Either DE or C0 can be taken for white; that is, density information about white is helpful. These data are stored in corresponding addresses, as shown in Fig. 13. Color codes include white, red, blue and black and consists of two bits. If there is need for in crease in color codes, the number of corresponding bits should be increased. The density information consists of 6 bits; four bits of which are enough for text information. It is obvious to change the number of bits corresponding to the image considered. Boundaries for color separation in Fig. 13 must be determined taking the output variation of the line edge into account; otherwise, unwanted color ghost (kind of incorrect color forming at the edge of back or other letters), is produced. Generally, color separation boundaries are fixed, causing great variation in color depending on way of boundary setting. This gives a great influence on the separation into multiple colors. To eliminate variations in the results of separation into multiple colors, care must be taken not to allow: (a) Variations in the light source's emission spectrum (b) Variations in the lens's chromatic aberration (c) Variations in cutoff wave length of the dichroic prism Item (a) has already been described. Care must also be taken not to allow fluorescent lamps to generate Ar spectrum at lower temperatures, which may sometimes happen. This example uses a fan heater to keep the temperature of the fluorescent lamp tube constant. The lamp's wall temperature is set in the range of 30°C to 80°C (range of 40°C to 80°C being desirable). Item (b) is described later. Problem of (c) is generally attributable to dissatisfactory management of variations in the membrane. It is desirable to allow variations to be in the range of +/-15 nm or more desirable +/-10 nm with respect to the cutoff wave length set; any other value outside the ranges may vary red and black boundary or blue and black boundary in the original image greatly by variations of the prism's cutoff wave length. This example conducts color separation by use of two signals: VR and VC. Another available method uses color separation axis f1 (VR, VC) and f2 (VR, VC). In using color separation axes in calculation, the generation of isolated noises with different colors, which is liable to happen due to different addresses, must be taken into account if noises are superimposed onto VR and VC. To pick up a certain color or any other colors than red, blue and black, the color separation maps are prepared which is different from those in this example, so that one of them can be chosen as required. Another method is to install color separation ROM (ROM pack, practically) which can be replaced. Fig. 14-A, -B show 3-color maps, and Fig. 14-C, 4-color map. As the map data, it is preferable to use data obtained after gamma correction. Fig. 16 shows an example of gamma correction curve. The curve L2 is an example with γ < 1, while the curve L3 is an example with γ > 1. Fig. 15 shows a specific example of the color separation circuit 35. As shown in Fig. 16, three correction curves L1 to L3 including no-correction case (γ = 1) are used with color separation ROMs 35A to 36C. In each of these ROMs the same color code data and density data after gamma correction obtained according to each correction curve are stored. Which gamma correction curve is to be used is selected by the selection signal supplied to the terminal 37. If the color separation ROM has a large capacity, each data of the color separation ROMs 36A to 36C can be stored. Fig. 17 shows another example of the color separation circuit 35. This example uses a gamma correction ROM 39B which stores gamma correction data shown in Fig. 16. The color separation ROM 39A stores color code data shown in Fig. 13 and density data before gamma correction. Color code data and density data are read as required. Density data is equipped with the specified gamma characteristic; both gamma-corrected density data and color code data are written into the RAM 38. Image signals VR and VC which have been color-separated and shade-corrected, are supplied as address data of the RAM 38; the color code data and density data determined by the address are read. The density data which has been read is gamma-corrected by the gamma correcting ROM 39B, and the image signal after gamma correction can be immediately obtained. As shown in Fig. 16, the gamma-correcting ROM 39B stores density data used to select and provide gamma characteristic by the selection signal from the terminal 37. The address data used for reading from the ROM 39A or writing into the RAM 38 consists of the address generating circuit 34. Next, the color ghost correcting circuit 300 is described. This circuit is used to eliminate color ghost for image data colors of which have been separated. There are many causes for color ghost generation; major of which are: (1) discrepancy in two CCD pixels (due to dissatisfactory mounting accuracy and ageing); (2) difference in cyan and red image multiplications; (3) Difference in cyan and red output levels attributable to lens's chromatic aberration; and (4) noises. Fig. 18 shows an example of color ghost generation. In this example, Japanese letter " (sei, sex)" is picked up and color ghost generated after color separation is shown. This example depicts that the color ghost of red and blue appears at the edge of black line, that of black appears at the edge of blue line, and that of red appears at the edge of red line, as shown in Fig. 19-A through -C. Other color combinations produce different color ghosts. Take the above example to show the appearance of such color ghost. (1) Discrepancy in two CCD pixels (see Figs. 20 and 21) Such incorrect positioning of CCD pixels as shown in Fig. 20 will cause the appearance of red/blue ghost at the edge of black line, black ghost at the edge of blue line, and black ghost at the edge of blue line. To prevent them, no discrepancy is allowed in arrangement of two CCD pixels. Usually, arrangement should be made within one pixel, or more desirable, 1/4 pixel. This example has realized this by use of a jig to arrange these pixels precisely and by use of adhesive to adhere them. Figs. 22 onward show an example of this method. The lens mirror body 801 is housed in the V-letter section opened vartically toward the top of the support material 801a, and then fixed by the clamp fitting 801c, and mounted onto the predetermined position of the unit board 810. The support material 801a rear side is equipped with mounting surface 801c that allows the prism 802 front side to stay. The prism 802 supported by the mounting material 802a can be fixed to the mounting surface 801b by screws. The mounting surface 801b has been produced by a simple machining process and provides extremely high accuracy of both distance to the lens mirror body 801 and perpendicularity for its light axis. This enables correct image forming, from the predetermined light image, on the light receiving surfaces of the CCDs 104 and 105 through the prism 802. As shown in Fig. 23, the discrepancy in the plain squareness R1 and R1' (inclination of the plain square R1 and R1' of the dichroic surface for the lens axis) dichroic surface produced by the plain 801b with respect to the light axis of the lens mirror body 801 and the plain 802a facing the lens of the prism 802 is given by the resolution MTF obtained by the signal output (y, x) of white/black lines for the white background, like: MTF = (y - x/y + x) x 100% An inclination of 10" means a decrease of 9% and an inclination of 30" means a decrease of 15% or more, preventing smooth pickup of white/black discrimination signal. Thus, holding a satisfactory surface accuracy is very important (one possible construction is to have the prism surface contact with the edge of the lens mirror body). CCDs 104 and 105 for the prism 802 are fixed by adhesive via the mounting materials 804 and 806. Fig. 24 shows a working example for the cross section of the key part. In this example, CCDs 104 and 105 are fixed to the image forming section via the mounting materials 804a and 804b fixed symmetrically on the both ends of the prism 802 by use of adhesive. Mounting materials should have a small coefficient of linear expansion because: (1) this prevents pixel discrepancy that may happen by change in temperature must be prevented and (2) this prevents occurrence of cracks on the prism caused by internal distortions of mounting materials due to difference in coefficients of linear expansion of mounting materials. Pixel discrepancy due to change in temperature can be reduced by providing the same requirements as each CCD mounting material; but a smaller coefficient of linear expansion is more desirable. Usually, a coefficient of linear expansion is 7.4 x 10 -6 (in case of optical glass BK-7). This implies that use of ceramic materials (coefficients of linear expansion of 7.0 to 8.4 x 10 -6 ), alloys with lower thermal expansion (e.g. invar alloy with coefficients of 1 ∼ 3 x 10 -6 ), niresist (coefficients of 4 ∼ 10 x 10 -6 ) is desirable, but use of aluminum material (25 x 10 -6 ) is not desirable. The above working example uses adhesive to fix the prism with the mounting material, and the mounting material with CCD. They are fixed and adhered after the adjustment of each CCD position with respect to a divided optical image, as shown in Fig. 24. In this figure, even iron with a large coefficient (12 x 10 -6 ) of linear expansion is not influenced by heat because of short length in the c direction. The d direction is the direction of line sensor arrangement. The prism and line sensor package use the same ceramic material, with the same coefficient of linear expansion. This construction has not produced pixel discrepancy. Adhesive of double-liquid type and optically-hardening adhesive are desirable; and ultraviolet-hardening adhesive is the most desirable. Optically-hardening adhesive quickens hardening time of adhesive simply by optical intensity, allowing ease of work, and cost reduction and product stabilization. Ultraviolet-hardening type provides almost no thermal change and ensures stable hardening. Ultraviolet radiation from a high-voltage mercury lamp on Three-Bond TB3060B (registered product name), Denka 1045K (registered product name) and Noland 65 (registered product name) has produced satisfactory results in environment test described later. Use of urethan Three-Bond of ultraviolet hardening type 3062B (registered product name) and LT350 (registered product name) has provided and improved resistance to humidity and ensured strength compensation. By use the above method, pixel discrepancy was reduced within 7/4 = 1.75µ, where one pixel is 7µ. (2) Discrepancy of cyan-image and red-image multiplication Influence of chromatic aberration of lens must be taken into consideration when copying a color document. Chromatic aberration of lens appears especially at higher image portions since the position F where cyan image is formed differs from the position E where red image is formed in conducting separation into optical wavelenghths of cyan and red colors, as shown in Fig. 25. For some lenses this results in discrepancy of a single pixel. (3) Difference in cyan and red levels Without design for improvement of lens's chromatic aberration, MTF values for cyan and red colors may become larger due to large chromatic aberration. Practically this appears difference in output signal level of CCD. Assume that 6-bit analog/digital quantization is conducted in picking up a black line, cyan and red output signal levels should be such that: |Vr - Vc)| ≦ 10 (levels), or more desirable, |Vr - Vc| ≦ 6 (levels), in mounting CCDs. This will reduce color ghost in some extent. However, complete elimination of color ghost is almost impossible when considering variations in performance of lenses mass-produced and variations CCD mounting precision. As a result, electrical correction of color ghost is made by use of color codes after color separation. To eliminate color ghost, the color pattern method is used since fixed color ghost appears for the original color like: Original: Black → Color ghost: Red and blue Original: Red, blue → Color ghost: Black with the color pattern method, the original color can be identified by knowing how a color for a certain pixel and those for its surrounding pixels appears (pattern). Fig. 26 shows an example which determines the color pattern of the target pixel and its surrounding pixels, and the color of the target pixel to be determined at that time. For No. 1 which has a color pattern of white and black at its edge, the blue color of that pixel is assumed to be a color ghost produced at the black edge. Likewise, for No. 3, red is assumed to be color ghost of black color. Accordingly, for Nos. 1 and 3, that pixel color is changed from blue or red to black. On the other hand, for Nos. 2 and 4, no color ghost occurrence is assumed, and the color of that pixel is directly output without being changed. It is difficult to implement such processing by use of an arithmetic circuit. In effect, this example uses LUT (look-up table) in ROM form. One or two-dimensional system can be used for color pattern. Assuming that the number of colors be N and the number of surrounding pixels including that pixel M, the number of color pattern is: N M This means that use of the 2-dimensional system increase M extremely and is not practical. In other words, use of the 2-dimensional system can provide less surrounding pixels in both primary and secondary directions, with demand for more patterns. Fig. 27 indicates the relationship between size and color pattern. This example uses single-dimensional color patterns of a size of 1 x 7 (N = 4, M = 7) and conducts color ghost elimination in the primary scan direction and in the secondary scan direction, independently. Since there is no difference between color ghost appearance in the primary direction and the secondary direction, the example uses the same color pattern both in the primary scan direction and secondary direction. This examples uses a color pattern with a size of 1 x 7, as described above; however, use of color patterns with smaller sizes, like one with 1 x 5, is possible. The color pattern with a size of 1 x 5 can eliminate color ghost of a single pixel, while the color pattern with a size of 1 x 7 can eliminate color ghost of two pixels. If a color pattern with a size of 1 x 7 is used, the the color code is entered as an ROM address. For such color pattern as: the color patter is like: White White Blue Blue Black Black Black 11 11 01 01 00 00 00 And the address is: 3D40 As shown in Fig. 26, the address contains the black code: 00 By use of this, table look-up work is made. Since a 14-bit address is required for a pattern of 1 x 7, a bipolar ROM should meet the demand for entry of an address of 14 bits and a color code of 2 bits. However, bipolar ROMs with such a large capacity cannot easily found and would be very expensive if any. The working example shows the case where ROM is searched by the first one pixel, and six other pixel codes are used to perform table look-up work. In other words, this example calls for two ROMs; the first of which starts with black (BK) and blue (B), while the second of which, red (R) and white (W). The first ROM (black/blue ROM) Starting address code black BK (00), blue B (01) Address contents The second ROM (red/white) Starting address code red R (10), white W (11) Address contents Since the color pattern of Fig. 26 starts with white color, the second ROM is selected. A higher-speed, larger-capacity ROM may have all the color patterns. Another way is to use four ROMs which is selected for starting pixel for table look-up work. One available high-speed, large-capacity bipolar ROM is MB7143/7144 produced by Fujitsu, Ltd. With a lower-speed, large-capacity EPROM, data are transmitted to multiple SRAMs prior to operation, through which color ghost correction can be made. Fig. 28 shows and example of the color ghost correcting circuit 300. This color ghost correction is made both in the primary (horizontal) scan direction and the secondary (vertical) scan direction. This example shows the case where color ghost correction is made in both the horizontal and vertical scan directions by use of image data for 7 pixels in the horizontal direction and 7 lines in the vertical direction. The color ghost correcting is made only for color codes of the image data. Color codes read from the color separating ROM is first supplied to the ghost correcting circuit 300A in the primary scan direction. As a result, color code data are supplied successively to the shift register of 7 bits for parallel operation. This parallel color code data of 7 pixels is supped to ROM for color ghost eliminating in the horizontal direction where ghost elimination is performed for each pixel. This is a description of an example of use of ROM302. Upon the completion of ghost processing, the latch circuit 303 is used to latch operation. On the other hand, the density data from the color separating ROM is supplied to the latch circuit 306, through the shift register 305 (7-bit configuration) for timing control, in which data transfer requirements are determined so that color code data followed by density data in serial data. To the line memory 310 in the color ghost compensating circuit 300B, serial processed color code data and density data are supplied. The line memory 310 to eliminate color ghost in the vertical direction uses 7-line image data. A 8-line memory is used for real-time processing. Of course, a 7-line memory can be used for real-time processing. A 8-line color code data and density data are separated by the gate circuit group 320 installed at the later stage. The gate circuit group 320 provides gate circuits 321 through 328 corresponding to line memories 311 through 318. Output data controlled for simultaneous operation by the line memory 310 is separated into color code data and density data by the gate circuit group 320. These separated color code data are supplied to the selecting circuit 330 where 7 (of 8)-line color code data is selected for use of color ghost elimination. If line memories 311 to 317 are once selected, line memories used are successively shifted to 312 to 318 at the next step, and so on. Selected 7-line memory color code data controlled for simultaneous operation is supplied to the next-stage ROM 340 for ghost elimination in the vertical direction, where color ghost is eliminated. Then, latch is conducted by the latch circuit 341. On the other hand, the density data separated by the gate circuit group 320 is supplied directly to the latch circuit 342, where it is timing-adjusted with color code data before being output. The next description is related to the resolution correcting step given as another example of image processing. This resolution correcting has been designed for being conducted after color separation. The conventional color separation used to be conducted after digitizing image data as described before, and this calls for resolution correction prior to the digitization. Color image processing apparatus with this method of color separation use multiple CCDs to pick up color-separated images on the document and must perform resolution correction for each CCD output. In other words, multiple circuits are needed for resolution. In addition, optical lens's MTF is not the same for each color separation work, making MTF correction parameters different for each resolution correction circuit. The apparatus according to the present invention permits resolution correcting to be conducted after color separation but before digitization. The information to be handled is one, so this way of color separation provides advantages for practical use including compactness of circuit size and simple procedure for determining auxiliary parameters. Generally, deterioration of MTF in recording and reproduction of image is attributable to the problems relating to: (1) Optical system (2) Optical travel system (3) Processing circuit (4) Recording system Problem (1) is related to the deterioration of optical performance attributable to lens' MTF (for wavelength range, change for image height, allowance for image forming position and precision accuracy), prism surface precision, CCD mounting precision, CCP chip warp, and spectral change of light source. Problem (2) is related to optical mirror vibration and change in travel speed. Problem (3) includes signal waveform distortion attributable to capacity of the analog circuit, especially, signal distortion caused when passed through the transmission line. Problem (4) is related to: Laser beam diameter and shape Toner characteristic of development onto light-sensitive drum (amount of toner adhered, toner density, toner grain diameter, toner color, etc.) Transfer characteristics (transfer ratio and transfer characteristics onto transfer paper) Fixing characteristic (toner diameters before and after toner fixing) Among above major problems, optical and optical travel systems are main factor which provide direct influence on the deterioration of resolution. Fig.29 shows MTF values (before correction) in both the primary and secondary scan directions, wherein horizontal axis represents resolution pattern (dot/mm) and vertical axis represents MTF value. These characteristics are measured values obtained when white/black patterns with space frequencies of 2 to 16 dots/mm have been scanned. In this case, MTF has been defined as follows: MTF = (W - BK)/(W + BK) (%) where W indicates white signal, and BK, black signal. As revealed in Fig. 29, deterioration in MTF is more obvious in the secondary scan direction than that in the primary scan direction. To perform correction in similar extent, the amount of correction in the primary direction is preferably adjusted to be twice to four times that in the secondary direction. MTF of 30% or more is needed to improve reproduction of fine lines of image. Then, as a resolution means to perform correction in similar extent in both direction while keeping satisfactory reproduction of fine lines, the resolution correction means is constituted by a weighted addition of the target pixel and its surrounding pixels. As the resolution correction, in the case of performing convolution calculation in the primary and secondary scan direction with 1 x 3 pixel 1-dimensional filter coefficients, such filter coefficients used for the optical scan system as shown in Fig. 2 are listed as shown below. 1/2 (-1 4 -1) (a) 1/4 (-3 10 -3) (b) 1/1 (-1 3 -1) (c) 1/2 (-3 8 -3) (d) 1/1 (-2 5 -2) (e) Filter coefficients (a) to (c) used in the direction of the primary scan provide satisfactory results, while filter coefficients (c) to (e) provide satisfactory results with respect to the direction of secondary scan. In the following type of filter, if the filter coefficients are represented with weight x as follows: [0 1 0] - x (1 -2 1) = [-x 2x +1 -x] x for the direction of primary scan is preferably set to be: 1/8 ≦ x ≦ 7/8, and x for the direction of secondary scan is preferably set to be: 1/2 ≦ x ≦ 7/4. As a result of combinations of above filter coefficients (a) - (e) in the directions of primary and secondary scan, (a) or (b) for the primary scan direction with (c) or (d) for the secondary scan direction was found most desirable. Synthesis of single-dimension filters is represented by: where x ○ designates convolution calculation. An example of desirable filter coefficients is: To reduces the number of calculations by a practical circuit, diagonal coefficients have been made zeros, like: The following filter coefficients were desirable when coefficients are constitued with integers to make the circuit simple. It is preferable to adopt the convolution filter using 3 x 3 pixels image data as indicated above as the resolution correction means. Matrix representation of filter components (left) and their corresponding pixel positions (i, j) (right) is as follows. With respect to the pixel density Iij of the target pixel (i, j), look at eight pixels surrounding the (i, j) pixel. Represent new density value with Iij which is obtained by referring the pixels (i-1, j-1) to (i+1, J+1): where Δ = 1 and Cij is a filter coefficient, taking a, b, c ... i. An example of filter coefficient to obtain the abovementioned practical correction is: To provide larger correction values, filter coefficients can be set accordingly. Fig. 30 presents results of correction by use of the convolution filter with the above correction coefficients. Fig. 31 shows an example of block diagram of the resolution correction means 450 using this convolution filter. This block diagram with a 3 x 3 matrix uses two line memories 451 and 452 along with 9 latch circuits 461 to 469. The first adder 470 and the multiplier (bit shift circuit) 471 are used to perform convolution of (1-row, 2-column) and (3-row, 2-column). The second adder 473 is used to perform convolution of (2-row, 1-column) and (2-row, 3-column). Likewise, the multiplier 472 with a 3-bit shift circuit is used to perform the operation of (2-row, 2-column). Use of the third adder 474 and fourth adder 475 produces new density values Iij convoluted. The following are some modifications of the resolution correction means 450. Addition or multiplication can also be done by use of an ROM. This example conducts resolution correction after color ghost processing; however, it can be done at any stage between color separation and multivaluing. The line memory can be commonly used for the one for color ghost correction. Resolution correction can be done at the same time as control of laser beam power for color ghost correction. This improves reproducibility of fine lines. The output unit 700 to be described later has a selection switch on its operation/indicator section 202 to perform resolution correction and power adjustment at the same time. In the future, digital signal processor (DSP) will be also used. The examples use 1 x 3 (1-dimensional) and 3 x 3 (2-dimensional), but filters with any size can be used. Filter coefficients may not be fixed; they very depending on how picture quality is deteriorated. In addition, the method is effective not only for monochrome image but for color image and image from a contract-type image sensor. The next example of image processing is a partial color conversion. Partial color conversion is an editing method in which image in the region specified by color maker or outside the region is copied in the marker's color. Conventional method is to perform positioning by use of a digitizer. Then, scanning is performed for an original picture. Operation of switches for positioning data entry is made for every time of positioning. The positioning is made not for all shapes but for a square or rectangle. The partial color conversion described below allows an arbitrary region (indicated by a marker) to be copied in the marker's color. For example, specifying the region by a red marker, as shown in Fig. 32, the region a is automatically detected and the image in the region a is copied in the marker's color red. The outside of the region a is copied in white/black color. The marker color can be blue. The partial color conversion is performed for a white/black document, as one example for easy consideration. To copy the image in the specific region a, it is necessary to detect marker signals BP and RP (actually, color code data is used as the marker signal) indicating color marker region, and region signals QB' and QR' indicating the region a, as illustrated in Fig. 33. Basically, the region signal indicating the region to be carried out color conversion is detected by obtaining a common marker signal P' representing the region being "rise to fall" of marker signal common to the region signal Q for the previous line, and then by ORing the region signal Q with the common marker signal P'. This is illustrated in Fig. 34 (a) and (b). In the case where there is a single loop having no branch as shown in Fig. 34 (a) and (b), obtaining the common marker signal P' from the rise to fall signal produced by ANDing between the region signal Q and the marker signal P provides the desired result. If there is a branch for a single loop like in (c), this method does not give the desired result. In this case, the fall signal is obtained by check in the direction opposite to CCD reading. Checking the fall signal of the marker signal in the direction opposite to the CCD reading provides a correct region signal even if the loop is branched. Of course, this is applicable to the examples (a) and (b). Simply outputting the blue and red region signals will cause red and blues letters to be superposed on black letters. In addition, this method does not provide desirable result if blue and red markers come together. This calls for region determination for each color scanning. This scanning is done for the case where blue and red markers come together and the case where these markers do not come together. Fig. 35-1 shows the case where blue and red markers do not come together: The picture information is picked up only if black, blue and red region signals are "1" as shown in Fig. 35-1. For example, in red copy mode, picture information being selected during the red region signal being "1" is recorded with red color. Fig. 35-2 shows the case where blue and red markers come together. Fig. 35-2-(a) shows the case where red marker is in blue marker, while Fig. 35-2-(b) shows the case where blue marker is in red marker. In both cases, inside color region is prepared to be outputted correctly. Similar to Fig. 35-1, the information is picked up if the region signal for each scanning is "1" and recorded in a specific color. The circuit design has been made taking both (1) and (2) into account. Hereinafter, a detailed embodiment of circuit arrangement will be explained. The partial conversion means comprises the color data selecting circuit 500B as well as the region extracting circuit 500A, as shown in Fig. 1. The color data selecting circuit 500B is intended for selecting density data to be developed with color that corresponds to the copy sequence (development sequence) for partial color designation operation, and for selecting density data to be developed with color that corresponds to the copy sequence for ordinary copy operation. Fig. 36 presents its specific examples, in which each bit for color code data obtained by scanning color marker is supplied to the color marker detecting circuit 501 to check for presence of a specific color marker. The working example represents the case where two colors, red and blue, are used for markers, and the marker signals BP and RP are detected. The marker signals RP and BP are supplied to the pre-processing circuits 502 and 503, respectively, so that they are marker signals dedicated to the designated region. The pre-processing herein means a kind of signal-waveform shaping. The working example presents the pre-processing circuits 502 and 503 consisting of the circuits 504 and 507 to correct portions not clear, the noise correction circuits 505 and 508 (both in the primary scan direction) and the circuits 506 and 5039 to correct marker breaking in the secondary scan direction. In the correction of color marker which is not clear, a color marker portion (which is not clear) of 16 dots or more is corrected, while in noise correction, a data absence of 8 dots or less is corrected. The marker signals RP and BP which have been waveform-shaped are supplied to the region extracting section 520 with the color codes where the gate signal S for extracting density data, generated based on the region signal that indicates the inside of the designated region a, is outputted for each scan line. The following presents descriptions of a more specific configuration. Fig. 37 shows an example of the color marker detecting circuit 501, designated to detect the marker's color by scanning the marker. The blue color code data is represented by the binary bit data of "01", while the red color code data is "10". As illustrated, lower-order-bit data and the inverted data of higher-order-bit data by the inventer 511 are supplied to one AND circuit 513. Likewise, higher-order-bit data and the inverted data of lower-order-bit data by the inverter 512 are supplied to the other AND circuit 514. In addition, the ANDed output of the vertical valid region signal V-VALID and size signal B4 is supplied to each of the AND circuits 513 and 514 as gate signals. 515 indicates an AND circuit. As a result, for the blue marker, the terminal 516 provides the blue marker signal BP which has a pulse width corresponding to the marker contour thickness. Similarly, for the red marker, the terminal 517 provides the red marker signal RP. An example of the marker signals are indicated in Fig. 33. Fig. 38 presents an example of the region extracting section 520. The region extracting section 520 consists of the first region extracting section 520A and the second region extracting section 520B, each of which has the data storage circuits 521A and 521B, respectively, and region arithmetric circuits 522A and 522B, respectively. In addition to the function to extract a blue marker region, the first and second region extracting sections 520A and 520B both have a function to extract a red marker region. This description is presented with respect to blue marker region extraction as one example. A current marker region signal of the current scan line is formed by calculating based on the latest region signal obtained by the most recent scan and the current marker signal obtained by the scan of the current scan line. To implement this, calculation must be done by use a period for at least three lines. Thus, the first data storage circuit 521A must have the function to store the latest region signal for one line which is the last data of the most recent scanned line, the function to store the first region signal of two sets of regional signals (actually, FF outputs) formed by calculating the current marker signal BP and the latest region signal, and the function to store the current region signal of the current scanned line obtained by calculating these two sets of regional signals (FF - output signal BN0 and BN1 in Fig. 39) In the working example, the second regional signal of two sets of regional is formed by reversely reading line memories of the second data storage circuit 521B. To attain above memory function, the required number of line memories is 16. Further, for detecting the red marker the total number of 32 line memories are to be prepared. As a result, the first data storage circuit 521A has a pair of memories 525 and 526, each of which consists of 8 line memories. To select each of them for line, a pair of Schmitt trigger circuits 523 and 524, a pair of data selectors 527 and 528 and the latch circuit 529 are installed. To the first data storage circuit 521A, the three kinds of signals consisting of regional signals (FF - output) obtained by the first region arithmetic circuit (530B, 530R), region signal (QB, QR) obtained by the OR - circuit 534 and marker signals (BP, RP) are supplied as input signals. In the first region arithmetic circuit 530B, the current blue marker region signal QB' on the current scan line n is formed by the just previous region signal QB and the current marker signal BP on the current scan line. For convenience of description, taking the scan line n into account as shown in Fig. 33, region signal QB (region signal of the scan line (n - 1)) and the marker signal BP have the relationship as shown in Fig. 39-B, -C. These signals are stored line by line onto the memory 525. For the next scan line (n + 1), these signals are read through the data selector 527 and the latch circuit 529 (Fig. 39-D, -E). A pair of the signals QB and BP is supplied to the NAND circuit 531, and its NAND output PB1 (Fig. 39-F) is supplied to the D-type flip-flop 532 through its preset terminal PR. Likewise the region signal QB is supplied to the clear terminal L. As a result, the first FF (flip-flop) output BN0 (first region signal) as shown in Fig. 39-G is obtained. The first FF output BN0 and the marker signal BP are stored into the memory 526 successively, and for the scan line (n + 1), the Schmitt trigger circuit 524 is controlled to be kept active. The second region extracting section 520B performs the similar operation at the same timing, but all the memories incorporated in the section 520B are address-controlled for forward writing (ordinary order) and backward reading (reverse order). Accordingly, the output timing for the marker signal BP and region signal QB is W1 from the first data storage circuit 521A, while W2 from the second data storage circuit 521B, making reading speed little faster in this example (Fig. 39-H, -I). As a result, the second FF output BN1 outputted from the second region extracting section 520B is one as shown in Fig. 39-K. The marker signal BP and the second FF output BN1 are stored in the data storage circuit 521B. For the next scan line line (n + 2), the first FF output BN0, the marker signal BP and the FF output BN1 is read out (Fig. 39-L to -N). Since the memory installed to the second region extracting section 520B is intended for forward writing and backward reading, as described above, the read timing W3 for the first FF output BN0 and the read timing W4 for the second FF output BN1 agree in this example. Both of the signals are supplied to the AND circuit 533. With AND output AB and the marker signal BP (Fig. 39-N, -O) supplied, OR output QB' is obtained, as shown in Fig. 39-P. The OR output QB' is the very signal that shows the inside of the blue marker contour illustrated on the current scan line n. That is, the OR output is the region signal QB'. The region signal QB' is used as the region signal QB right before on the next scan line, so it can be readily understood that the signal is fed back to the data storage circuits 521A and 521B. Thus, use of a pair of FF outputs BN0 and BN1 obtained by making memory reading direction opposite to each other allows correct detection of the marker region. This is applicable to the detection of red marker, and description of the region arithmetic circuit 530R is omitted, provided that 535 is an NAND circuit, 536, D-type flip-flop, 537, AND circuit, and 538, OR circuit. Schmitt trigger circuits 523 and 524, memories 525 and 526, and data selectors 527 and 528 have been prepared in pair taking the presence of blue and red markers concurrently. These are selected by 2-line cycle selection signals supplied to the terminals A and B. The region signals QB' and QR' supplied to the output terminals are supplied to the region determining circuit 540 as shown in Fig. 40. The region determining circuit 540 is a control means for the region signal used to recording images as shown in Fig. 41, if the marker designation is like one shown in Fig. 41-A. In the periods I and V of the figure, white/black image is recorded, while in the periods II and IV, a black image is recorded as a red image. In the period III, a black image is recorded as a blue image by allowing density data gate signal S to be formed from region signals QB' and QR'. The region determining circuit 540 has flip-flops 541 to 544. Region signals QB' and QR' latched by the forward flip-flops 541 542 are supplied to their corresponding NAND circuits 545 to 548, while region signals QB' and QR' latched by backward flip-flops are supplied to their corresponding NAND circuits 545 to 548. To each of the NAND circuits 545 to 548, color code data CC indicating black color is supplied via the AND circuit 554. On the other hand, to the switching circuit 553, the BBR signal is supplied which shows the copying operation is done in what color. By inputting the region signals QB' and QR', obtained from the scanning line n as indicated in Fig. 41, into the forward flip-flons 541 and 542, the FF - output signals represented with A to D in Fig. 42 are outputted. FF - output BP and RP among above four pieces of FF - output signals are introducted into the backward flip-flops 543 and 544, thereby obtaining FF - output Q1 and Q2 indicated with H and L in Fig. 42. Above all FF - output signals are supplied into the NAND circuits. With A to C signals shown in Fig. 43, the first AND circuit 545 provides the first NAND output M1 as shown in Fig. 43-D. Likewise, the second NAND circuit 546 provides the second NAND output M2 shown in Fig. 43-G based on the E to F input signals in Fig. 43. As a result, the AND circuit 551 provides the gate signal S1 related to the period III shown by H in the Fig. 43. Similarly, I to K input signals in Fig. 43, provides the third NAND output M3 of the Fig. 43-L, while input signals in Fig. 43, M and N provide the fourth NAND output M4 in Fig. 43-O. As a result, the second AND circuit 552 provides the gate signal S2 (Fig. 43-P) related to the periods II and IV. With Q to S signals in Fig. 43, the fifth NAND circuit 549 provides the gate signal S3 (Fig. 43-T) corresponding to the periods I and V. One of the gate signals S1 to S3 is selected by the switching circuit 553 corresponding to the BBR signal that indicates the copy sequence. Accordingly, the gate signal S1 is selected for blue color recording mode, while the gate signal S2 is selected for red color recording mode. Likewise, gate signal S3 is selected for black color recording mode. Gate signals S1 to S3 form the switching circuit 553 are supplied to the color data selection circuit 500B shown in Fig. 44. First, the gate signal S and the color code data are supplied to the gate circuit 570. The gate circuit 570 consists of a pair of NAND circuits 571 and 572. If color code data is black, the gate signal S is gated, and either of this signal and BBR signalis selected in the selection circuit. Which signal is to be taken is controlled by the processed signal designated by the operation/indicator section 202 as shown in Fig. 74. With these outputs, density data is selected in the selection circuit 574 that corresponds to the color code data. In this case, white density data (always 1) of white color is selected in the period outside the period where there is no gate signal S. One example of this is that white data is always selected outside the period III in the blue color recording mode. As a result, blue image is recorded in period III alone in the blue recording mode, while red image is recorded in period II and IV in the red recording mode and periods I and V are recorded in black color in the black recording mode (Fig. 41-B). As a result of use of the region determining circuit 540, inside marker color is taken precedence. The region not overlapped is copied by the color of marker that designates the region not overlapped. Fig. 45 shows another example of partial color conversion having some modification with respect to Fig. 1. Namely, in the abovementioned embodiment as shown in Fig. 1, gate signals S1 - S3 are selected in accordance with the BBR signal representing the copy sequence in the switching circuit 553, thereby recording the image locating within the designated region with the specific color. In the embodiment as shown in Fig. 45, as mentioned later on, color code converting section 570 for converting color code data is provided in place of the switching circuit 553. In Fig. 45, 6-bit MTF-corrected density data is converted into a binary data (0 or 1) by the digitizing means 600. the threshold data (6 bits) used as a reference data for digitizing is set automatically or manually. The partial color conversion is image processing to record the information inside the region (in case of the working example, or outside the region) specified by a certain color. A red or blue color is used to specify the closed region. The means 500 is to perform partial color conversion in accordance with a key feature of the invention. It has the region extracting circuit 500A to detect the original region marked by a color marker on the document, the region determinating circuit 540 for judging the designated region from the extracted region signal, the code converting section 570 to convert the color code data in the extracted region into color code data in a specified color, and the color data selection circuit 500B to select binary output corresponding to the converted color code data. The selected binary data is supplied to the output unit 700 through the interface 40 whereby the image information in the corresponding closed region is recorded in a specified color. In this embodiment, the region extracting circuit 500A is constituted same with one indicated in Fig. 36, 37 and 38, whereby the region signal QB' and QR' can be obtained therefrom through the same circuit logic as shown in Fig. 39. In the region determining circuit 540 which is further shown in Fig. 46 in detail, the region determining signals Sl to S3 are obtained in response to the region signal QB' and QR' through the same circuit logic as shown in Fig. 42 and 43. The region determining signals S1 to S3 are supplied to the color code converting section 570 along with color code data. The color code converting section 570 includes an ROM where converted color code data stored at addresses determined by the region determining signals S1 to S3 and color code data, are referenced. Fig. 47 shows a relationship between color code data and their corresponding colors. The color code data converting section 570 is to convert image data in the region of each color into a coresponding color code data. Fig. 48 shows a data table of the ROM. For outside the specified region, monochrome color code data are output. Converted color code data are supplied to the coincidence circuit 581 illustrated in Fig. 49, in which the same converted color code data as the BBS signal indicating a copy sequence. The coincidence circuit 581 includes an ROM, an example of which is shown in Fig. 50. The output signal Q is supplied to the output signal control means 582 where control is not to provide the output signal Q if binary data ("1") indicating white color is provided. The output control means 582 may consist of an ROM. Assuming that a binary data is P and that a control ROM 582 output is R, contents of the ROM are set to provide the signals P, Q and R with the relationship as shown in Fig. 51. Fig. 52 shows an example of copy operation in which the designated region is detected, and Fig. 53 presents an example where some parts on a monochrome document are marked by red and blue colors. For a copy sequence of blue, red and black, color markers are detected in this sequence. In the copy mode, a blue color marker is first detected, and then black color code data in the detected region is converted into a blue color code data, and at the same time, the black color in the region is copied in blue color (steps a and b). Fig.54-A indicates the copy state for this operation. Next, when the red color marker region is detected, the black color code data is converted into red color code data, and the black color in the region is copied in red color (steps c and d). Fig. 54-B indicates the copy state for this operation. Finally, the information in black color in a region outside the detected regions is copied in black color (step e). Thus, as shown in Fig. 54-C, the color marker region is copied in that color; others are copied as in the original document. The inside or outside of the closed region specified by a specific color can be recorded in that color, and is very convenient for image processing. The color code of color signal corresponding to the image inside or outside the specified region is a color code data obtained after color conversion. This method of image processing is characterized by the capability of reproduction of the original image in the specified color by use of color code data stored directly into the memory. This converted color may be used a color signal for a CRT. Thus, this invention is very suited to a color image processing apparatus of simplified type. The following description is related to some modifications of partial color conversion. The partial color conversion is related the detection of the designated region and processing of image data or color in the specified region. This is applicable to partial region extraction, erasing, reversing, mirror-image, enlargement, reduction and position movement and their combination. It is possible to carry out processing for the detected region according to the predetermined contents. The background color of the document is white, but other colors are allowable. Red colors (including orange and pink) or blue colors are appropriate for color markers since these color are not liable to reproduction in normal copying. If no color marker can be used directly for the document, a transparent sheet can be used. As shown in Fig. 55, the designated region can be painted over by color marker. The following description is related to automatic and manual density adjustment for image processing. A conventional method to set image density controls level selection knob on the operation period, and adjusts bias voltage at the time of development and light intensity of the light source to obtain the image with the predetermined density. However, only an experienced person familiarized with copying machine operation can succeed level setting at one time; other persons had to make wasted rials before obtaining satisfactory level. To solve this problem, the automatic density system has been developed. This system determines the density of document based on the information about density obtained by the pre-scanning process. One of the drawbacks of this system lies in the process of detection of the information about density by pre-scanning, which makes the initial copying time longer and thus does not so improve productivity in copying operation. To set document density real time, document density histogram is produced. When the density histogram as shown in Fig. 56 has been obtained, the threshold for multivaluing (digitizing, for example) is calculated by level that provides the frequency of peak in the histogram. This calls for the counting of frequency of peak for each density level, increasing circuit size. The new method has the threshold determining mean 610 which sets appropriate document density real time without pre-scanning and without an increase in circuit size. The threshold determining mean 610 is installed in conjunction with the multivaluing circuit 600B. The major feature of this mean lies in the determination of threshold value line by line based on maximum value DH and minimum value DL of density data in each scan line. In color copying which carries out in the sequence of blue, red and black, density data of the pixel corresponding to the color to be currently copied is sampled, and both maximum and minimum values are obtained for each color. The following shows one example of calculation of threshold for digitizing. Ti = ki (DH - DL) + αi + DL where i = blue, red or black k = coefficient in the range of 0.1 to 0.8, 0.2 to 0.6 being desirable α = correction value. Both k and α vary depending on color, and obviously on density data stored in the map for color separation above described. For example, k may be 1/2 to 1/3 for black, and 1/2 for red and blue. α may be -10 for black, and 2 to 6 for red or blue. Noises may be mixed up in calculation of the maximum and minimum values. To prevent this, density data which have not been sampled can be used if there is drastic change in density data, or a mean value of two adjacent density data can be used. Also to prevent calculated threshold from being changed drastically, the mean value of the thresholds for multiple lines can be used as a threshold for the current line. In multivaluing, it is obvious to select coefficients k and α for their thresholds. To copy the original picture in a signal color, coefficients k and α vary depending on color. In other words, the original document usually includes letters in black color, with less letter in other colors. Determination of threshold based on black color results in scattered reproduction image in red or blue color. On the other hand, determination threshold based on red or blue color results in dissatisfactory of reproduction image in black color. To prevent this, thresholds must be manually set for each color to address them in color code for each pixel during digitizing, if the automatic threshold means 610 is not provided. If the automatic threshold means 610 is provided, the density data arrangement of the color separation ROM should be changed, and other color images should be satisfactorily reproduced based on thresholds selected in copying in designated colors. The following shows specific example of the automatic threshold determining means. Fig. 57 shows an example in which a ROM is prepared to save a threshold obtained for each color by the threshold calculation expression, and threshold data is selected from the maximum and minimum value of the line. In this figure, 611 indicates the ROM which stores a threshold for each color. The density data is supplied both to the maximum value calculation circuit 612 and the minimum value calculation circuit 616. In the following example, the maximum value calculation circuit 616 is taken, since this is applies to the minimum value circuit 612. The density data of the current pixel and that of the previous pixel latched by the latch circuit 614 is supplied to the switching circuit 613. The density data of the current pixel and that of the previous pixel are supplied to the comparator 615 for comparison, where either of them is selected as an output. If the density data of the current pixel is larger than the other, that density data is selected. This comparison is conducted for all the pixel to find the maximum value DH. Likewise, the minimum value calculation circuit 616 finds the minimum value DL from results of comparison of minimum values by the comparator 619. The maximum and minimum values DH and DL obtained for one line are used to address the threshold ROM 611. Selection of the threshold for which color is conducted based on the BBR signal supplied to the threshold ROM 611. As shown in Fig. 58, ROMs 621 to 623 which store each threshold data for each color may be prepared to select threshold data by the BBR signal. This configuration needs the encoder 624 which encodes the BBR signal. The above expression can be used to perform calculation of the threshold successively in real-time mode. Fig. 59 shows an example of this method. With the maximum value DH and the minimum value DL obtained as above, the density width, (DH - DL), is calculated by the subtracter 625, the resultant density width of which is supplied to the first ROM 626 that stores the coefficient k where multiplication of the result and a coefficient selected by the BBR signal is performed. Then, the value obtained by ki x (DH - DL) is added to the minimum value DL in the adder 627. On the other hand, data of the coefficient ROM 628 that stores αi is selected by the BBR signal, and is supplied to the second adder 629, along with the addition output, and the final threshold Ti is obtained. A pre-processing circuit for density data, like an averaging circuit, may be installed to prevent noises from being generated. Also, a post-processing circuit may be installed for the calculated threshold Ti. For color copying in a single color (all black, all red, or all blue), the threshold for black color can be used for digitizing the other colors. In other words, for copying in single color, black code alone is used for satisfactory reproduction of black image. However, the problem of this method lies in that a low-density color, like a fluorescent pen color, cannot be easily reproduced. This problem is solved as follows. As shown in Fig. 60-A, density corresponding values for color separation map are arranged with (VR + VC)/2 for red, bue and black colors. Also, as shown in Fig. 60-B, these density values are shifted for each color, and fit density values for red and blue colors to black color. Then, digitizing for all the colors is conducted for the same threshold. The threshold selection signal is supplied form the operation/indicator section to digitizing circuit 606B, where the threshold for EE mode or that for manual mode is selected. Normally EE mode is assumed. If EE mode is reset, the address of the threshold ROM 630, manual threshold determining mean, is assigned to output the desired threshold for digitizing. To code a photo image, a dither matrix of 8 x 8, for example, can be prepared as a threshold ROM. Also, the counter output that designates a row and a column can be used to control the threshold ROM 630 address. The image data can be made ternary to represent gray color. The binary image signal is supplied to the output unit 700 through the interface circuit 40. The following description is related to the configuration and operation of the interface circuit 40, referring Fig. 61. The interface circuit 40 consists of the first interface 41 to receive binary data and the second interface 42 to send binary data from the former interface. To the first interface 41, the horizontal valid signal H-VALID and the vertical valid signal V-VALID are supplied along with the clock of the predetermined frequency (6 MHz, in this example) from the counter clock circuit 44. This allows binary data to be sent synchronously with the CCD drive clock to the second interface 42, only when the horizontal and vertical valid signals are generated. The counter clock circuit 44 generates the timing clock of the primary scanning sychronously with the optical index signal. The second interface 42 is used to send binary data from the first interface 41 and other image data to output unit 700. Other data include: test pattern image data from the test pattern generating circuit 46; patch image data from patch circuit 47; and control data from the printer control circuit. The test pattern image data is used during check of image processing. Patch image data for toner density detection is used during patch processing. The test pattern generating circuit 46 and patch circuit 47 are both driven by clock from the counter clock circuit 44, whereby the timing with the binary data from the first interface 41 is taken. The binary data from the second interface 42 is used as laser beam modulation signal, with respect to the output unit 700. Fig. 62 shows an example of the first interface 41 which a pair of line memories 901 and 902 to be used for digitizing in real time mode. To these line memories 901 and 902, the enable signal with 2 lines assumed to be one cycle is supplied, along with the predetermined address data from each of the address counters 903 and 904. CK indicates a clock for the address counter (Fig. 63-B). The enable signal forming circuit 910 is equipped with the AND circuit 911, as illustrated. To this AND circuit, the above clock CK is supplied along with the size signal B4 (in this example, the maximum size is B4, as shown in Fig. 63-A) which can be handled by this apparatus. Thus, the first the AND output Al (Fig. 63-C) is formed. On the other hand, the D-type flip-flop 912 is installed. The line signal SH (Fig. 63-D) is provided once for each line synchronizing with the deflector 935 installed to the output unit 700 is supplied to this flip-flop. As a result, outputs (shown as Q and Q ) with polarities (shown in Fig. 63-E and -F) are obtained from the Q and Q terminals. The output Q and the first AND output Al are supplied to the first NAND circuit 913, while the output Q and the first AND output Al are supplied to the second NAND circuit 914. The first NAND output N1 from the first NAND circuit and the second NAND output N2 from the second NAND circuit (Fig. 63-G, -H) are supplied as enable signals for line memories 901 and 902. Thus, each line memory 901 and 902 are write-enabled alternatively line by line. Outputs from the line memories 901 and 902 are controlled with respect to their output state by the 3-state gate circuits 905 and 906. The gate signal forming circuit 920 is installed for this purpose. The signal forming circuit 920 consists of a pair of AND circuits 921 and 922 and a pair of NAND circuits 923 and 924. Q and Q outputs and horizontal valid signal (H-VALID) (Fig. 63-I) are supplied to the second AND circuits 921 and third AND circuits 922 to form AND output A2 and A3 shown installed at the next stage, the vertical valid signal V-VALID (Fig. 63-L) is supplied along the these AND outputs A2 and A3. Also, the third output N3 (Fig. 63-M) is supplied to the gate circuit 905, and the fourth output N4 (Fig. 63-N) is supplied to the other gate circuit 906. As a result, the gate state is controlled line by line, and digitized image data for each line are read out from the first interface 41. The horizontal valid signal V-VALID and the vertical valid signal V-VAL are used to determine valid widths in the horizontal and vertical directions. The clock CK, the horizontal valid signal H-VALID, and the vertical valid signal V-VALID are supplied from the output unit 700. Fig. 64 shows the peripheral circuit of the output unit 700. The semiconductor laser 931 is equipped with its driving circuit to which the above binary data is supplied as a modulating signal. This signal causes laser beam to be modulated internally. The laser driving circuit 932 is controlled by the control signal from the timing circuit 933 so that laser beam is driven only in the horizontal and vertical valid sections. The signal that indicating the light intensity of laser beam is fed back to the laser driving circuit 932 so that laser is driven for a constant light intensity of beam. The point start the operation for laser beam deflected by the octahedron polygon 935 is detected by the index sensor 936. The conversion from the index signal to the voltage signal by the I/V amplifier; the index signal is supplied to the counter clock 44 to form the line signal SH and to control the timing for optical primary scan. Note that 934 is a drive circuit for a polygon motor; its on/off signals are supplied to the timing circuit 933. Fig. 65 shows an example which uses a laser beam scan (optical scanning unit) as an image exposure means. The laser beam scanner 940 possesses semiconductor laser 931 which is on/off-controlled according to color-separated image (for example, binary data). Laser beam from the laser 931 is entered into the polygon 935 consisting of a rotating polyhedron multi-sided mirror through the mirrors 942 and 943. The laser beam is deflected by the polygon 935, then is irradiated on the surface of image forming unit 11 through the f- lens 944 for image pickup. 945 and 946 are cylindrical lenses with angle of turn. The polygon 935 allows the laser beam to scan the surface of the image forming unit 11 at a constant speed in the predetermined direction a. This scan allows image exposure corresponding to the color-separated image. The f- lens 944 is used to obtain the predetermined beam diameter on the image forming unit 11. The polygon 935 can be galvanomirror or optical quartz deflector instead of the rotating multi-sided mirror. Fig. 66 shows the example of the developers 123 to 125 that can be used for the laser recording unit shown in Fig. 2. Here description is given with respect to the developer 123; it is applicable to the description of the other developers. In this figure, 421 shows a housing in which a cylindrical sleeve 422 is incorporated while being turned freely. In the sleeve 422 installed the magnetic roll 423 which has 8 sets of N and S poles. On the perimeter of the sleeve 422 contacted the layer-control piece 424 to obtain the desired thickness (10 to 500 m) of layer of developer adhering to the sleeve 422. The first agitating material 425 and the second agitating material 426 are installed in the housing 421. The developer D in the developer well 429 is satisfactorily agitated by the first agitating material 425 designed to rotate counterclockwise and the second agitating material 426 designed to rotate in the direction opposite to the first agitating material 426, while to superimpose each other. The agitated developer D is carried and adhering to the surface of the sleeve 422 by rotation of the sleeve 422 and the magnetic roll 423 in mutually opposite directions. With the developer D adhering to the image forming unit 11, electrostatic latent image formed on the image forming unit 11 is developed with non-contact state. During development, development bias signal supplied by the power supply 430 is applied to the sleeve 422. This development bias signal from the power supply 430 consists of a DC component which has been set to almost the same potential of non-exposure section of the image forming unit 11 and an AC component superimposed to the DC component. As a result, development is conducted by transferring and adhering the toner T of the developer D on the sleeve 422 alone on the surface of the image forming unit 11 which has been selectively made latent. 427 is a toner container, and 428 is toner feed roller. 431 shows a development region. A two-component developer is used as a developer. Under the condition where no development bias is applied, and the image forming unit 11 and development D do not contact each other, and vibration electrolysis is made by AC bias printing, the toner T is scattered and selectively adhering to the electrostatic image of the image forming unit 11. In development of images in blue, red, black, and other colors on the image forming unit 11, this non-contact development method will not damage a preceding toner image by a succeeding toner image, and realizes thin-layer development. Fig. 67 shows variations in surface potential of the image forming unit 11, assuming the charged polarity positive. pH shows an exposure section for image forming pair, DA is a non-exposure section for image forming pair, and DUP presents an increase in potential produced due to the adherence of the positive-charged toner T1 in the first development. The image forming until 11 produces a constant positive surface potential E after uniform charging by a charger. With the first image exposure using laser as an exposure source, the potential of the exposure pH decreases depending on its intensity of light. The electrostatic latent image thus formed is developed by the developing unit to which positive bias almost equal to the non-exposure section's surface potential E is applied. As a result, the positive charged toner T1 adhering to the exposure section pH with relatively lower potential and the first toner image is formed. In the region where this image has been formed, the potential decreases due to adherence of positive-charged toner T1, but will not normally be the same potential as the non-exposure section DA. Next, the second charging is made by the charger for the image forming unit surface on which the first toner image has been formed. As a result, the uniform potential E is obtained whether the toner T1 exists or not. The second image exposure is performed for the surface of the image forming unit 11. Likewise, the second toner image is obtained to which development for positive charged toner T2 has been made with a different color from the toner T1. After performing the same process three times, multi-color toner image is obtained on the image forming unit. This image is transferred onto the transfer paper P, and then heated or pressured to multi-color image data. In this case, residual toner and charge on the image forming unit are cleaned to be used for a next multi-color image forming unit. The developing process is to be conducted taking care not to allow developer layer to contact the image forming unit surface. There are some other methods than the electrophotographic method available for forming a multi-color latent image. One method is to form an electrostatic latent image by pouring directly onto the image forming unit by use of multiple electrodes; another is to form a magnetic latent image by use of a magnetic head. The described apparatus uses a 2-component developer consisting of nonmagnetic toner and magnetic carrier because it allows easy control of toner's frictional charging and excellent characteristic of development and adherence of any color to toner. The following methods for obtaining toner images can be considered can be considered by use of the image forming unit 11. First, one latent image is developed by one type of toner; toner is changed for each development process to obtain a multi-color toner image. Secondly, one latent image is developed successively by use of multiple types of toners, thus producing a toner image with two or more colors overlapped. Thirdly, two or more latent images are developed by use of toner of the same kind (the same one type or same some types), thus allowing synthesizing images. In the use of the above 2-component developer, the thickness of the developer becomes very thin: 2,000 m or less, or more desirable, 1,000 m or less, and 10 to 500 m, or more desirable, 10 to 400 m. In this case, the distance between the image forming unit 11 and the sleeve 422 is made smaller. Even if bonding force of the developer's carrier and toner and that of the carrier and the sleeve 422 are weak, the toner adheres to the sleeve 422 satisfactorily, preventing the toner to be scattered. By making the developer layer thinner and the distance between the image forming unit 11 and the sleeve 422 smaller, the vibration electrolysis required to scatter the toner can be adjusted lower. This also makes developing bias voltage lower. Thus, in addition to reduction in toner scattering, there is another advantage: capability of controlling leak discharge based on the development bias from the sleeve surface. If the distance between the image forming unit 11 and the sleeve 422 is made smaller, the electrolytic strength for the development region 431 (space where the image forming unit 111 and the sleeve 422 face) becomes larger, allowing satisfactory development for delicate tone variations or fine patterns. On the other hand, if the development layer is made thinner, the amount of toner to be carried to the development region decreases and the amount of development also decreases. High-speed rotation of the sleeve is effective for a larger amount toner to be carried. With a line speed ratio 1:10 with respect to the image forming unit 11 and the sleeve 422, the speed component which the developed toner provides in parallel with the latent image becomes larger resulting in directional development and deteriorated picture quality. This requires that the toner should adhere the sleeve with a density of at least 0.04 mg/cm 2 . Assume that the sleeve 422's line speed is Vsl, the image forming unit 11's line speed, Vd, and the amount of toner in the thin layer on the sleeve 422, Mt. The following requirement must be satisfied: |Vs1/Vd| x Mt ≧ 0.4 (mg/cm 2 ) |Vs1/Vd| ≦ 10. Taking the development efficiency into account, it is desirable to establish: |Vs1/Vd| x Mt ≧ 0.5 (mg/cm 2 ) |Vs1/Vd| ≦ 8. Furthermore, the results of experiment have showed that the following relationship should be established. |Vs1/Vd| x Mt ≧ 0.5 (mg/cm 2 ) |Vs1/Vd| ≦ 5. In this case, the ratio between the toner in the developer and the carrier should be so established that ratio of the total area of toner and that of carrier in the unit volume fall in the range of 0.5 to 2. With the above setting, the toner in the thin layer can be efficiently developed, stabilizing development condition, and obtaining satisfactory picture quality. As a means to forming thinner developer layer, the layer regulating piece 424 is frequently used, which consists of a pressure-contact plate lightly, elastically contacting the sleeve 422. The layer regulating piece 424 consists of an elastic plate so pressured that its end faces the upper side of sleeve rotation. By allowing the developer to pass the distance between the sleeve 422 and the piece regulating piece 424, the thinner layer is formed. Assume that the distance between the layer regulating piece 424 and the sleeve 422 is 0.08 mm or more. A constant volume of toner can be stably carried irrespective of mounting accuracy and mechanical precision. With a distance of 0.1 mm or more, the stability can be more improved. However, with a distance of 5 mm or more, it was observed that uniformity of developer could no longer be kept. The developer layer which has been made thinner is used to develop the electrostatic image of the image forming unit 11 carried to the development region, with the requirement of the following expressions (1) and (2) satisfied. |(vs1 - nωmh'/3)/Vd| ≦ 10 |(vs1 - nωmh'/3)/Vd| x mt ≧ 0.4 [mg/cm 2 ] where, Vs1 = sleeve line speed (mm/sec) n = No. of magnetic poles of magnetic roll ωm = rotation angular velocity of magnetic roll h' = height of magnetic brush (mm) Vd = line speed of image forming unit mt = amount of volume of toner adhering per unit area of the sleeve (mg/cm 2 ) Vs1, ωm are assumed to be positive if they are in the same direction with respect to be movement of the image travel forming unit. The height of magnetic brush is an average height of magnetic brush standing on the sleeve. More specifically, the sleeve line speed, Vs1, is in the range of 100 to 500 mm/sec. The number of magnetic poles, n, is in the range of 4 to 16. The revolution angular speed of the magnetic roll, ωm, is in the range of 30 to 150 radian/sec. The magnetic brush height, h', is in the range of 50 to 400 µm. The line speed of the image forming unit 11, Vd, is in the range of 30 to 150 mm/sec. The amount of volume of toner adhering per unit area of the sleeve, mt, is in the range of 0.4 to 1.0 mg/cm 2 . These are targets values are provided to attain satisfactory development; and vary depending on the distance d between the image forming unit 11 and the bias voltage. The requirement for desirable development is given as follows taking these factors into account. 5 ≦ Vp - p/d - h" ≦ 50 (kV/mm) where Vp - P = peak-to-peak voltage of AC bias (kV) d = distance between the image forming unit and sleeve (µm) h"= maximum height of magnetic brush (µm). The maximum height of magnetic brush is that of the magnetic brush on the magnetic pole in the sleeve 422. The units and circuits described above are all controlled by the first and second controlling sections 200 and 250 as shown in Fig. 68. The description begins with the second controlling unit 250. The second controlling section 250 is used mainly for controlling the image-reading system and its peripherals. The 251 is a microcomputer to control optical drive (2nd microcomputer). Communications between this and the microcomputer to control the main body is done in serial mode. The optical scan start signal from the first microcomputer 201 is supplied directly to the interrupt pin of the second microcomputer 251. The second microcomputer 251 generates various directive signals synchronously with the clock of the desired frequency obtained from the standard clock generator. In addition, the second microcomputer 251 outputs the threshold signal and BBR signal (color selection signal) for color recording. This microcomputer also supplies the following control signals. First, the signal to turn on or off the driving circuits of CCD 104 and CCD 105 is supplied to the power supply control circuit (not illustrated). Secondly, the predetermined control signals are supplied to the turn-on control circuit 254 for the light sources 85 and 86 used to irradiate light required for the document 81. Thirdly, control signal is supplied to the drive circuit 252 that drives the stepping motor 253 used for move the movable mirror unit (like 88). Forthly, control signal is supplied to the control circuit 256 for the heater 257. The second microcomputer receives data which show the information about light intensity, home position, and other data. The first microcomputer 201 is used mainly for controlling the color copying machine. Fig. 69 shows an example of input and output systems of the color copying machine. The operation/indicator section 202 receives a variety of input data including multiplication, recording position, and recording color, with display of them. A LED or other devices are used for the purpose of display. The paper size detecting circuit 203 is used to detect cut paper in the tray, to display it, and to automatically select the paper size according to document size. The drum index sensor 220 detects the rotation position of the image forming unit 11. The index signal from the sensor is used to control the timing of the electrostatic processing timing. The paper-out detection sensor 221 is used to detect whether there is paper or not. The manual feed paper-out detection sensor 222 is used to detect whether there is paper or not in the manual paper feed mode. The toner density detection sensor 223 is used to detect the toner density on the drum 11 or after fixing. Three toner residual amount detection sensor 224 to 226 are used to detect residual amount of toner of the developing units 123 to 125. Information about toner feeding is shown by the display device for toner feeding installed on the operation section. The temporary stop sensor 227 is used to detect whether paper has been correctly set tot the second paper feed roller (not illustrated) from the cassette during color copying machine operation. The paper eject sensor 228 is used to detect whether paper has been correctly ejected to the outside after the fixing. The manual paper feed sensor 229 is used to detect whether a manual paper feed tray has been set. If so, manual paper feed mode is automatically assumed. The sensor output from each sensor is taken by the first microcomputer 201, related data are displayed on the operation/indicator section 202, and the color copying machine is driven as required. The color copying machine is equipped with the motor 230 for development in red and blue colors, along with the motor 231 for development in black color only. These motors are both controlled by the directive signal from the first microcomputer 201. Likewise, the main motor 204 (drum motor) is controlled by the PLL-configured drive circuit 205 which is also controlled by the control signal front the first microcomputer 201. Development in colors requires that the predetermined high voltage be applied to the developer in operation. This calls for the installation of the high-voltage power supply for development, 232, and the high-voltage power supply for transferring and separation, 234, and high-voltage power supply for toner receiving, 235. To them, the predetermined high voltage is applied as required. Note that 237 is a cleaning roller driving section, 238 is the roller driving section for the first paper feed roller, 239 is the roller driving section for the second paper feed roller, and 236 is a motor for release contact for cleaning. And 240 is a driving section of separation claw. The second feed roller is used to carry the paper from the first paper roller onto the electrostatic latent image formed on the drum 11. The fixing heater 208 is controlled by the fixing heater on/off circuit 207 according to the control signal of the first microcomputer 201. The fixing temperature is read out by the thermistor 209, and usually controlled to be an appropriate temperature by the first microcomputer 201. 206 is a clock circuit (approximately, 12 kHz). The nonvolatile memory 210 installed in conjunction with the first microcomputer 201 is used to store data to be retained after power-off. Such data include total counter values and initial settings. Thus, the first and second microcomputers 201 and 251 performs a variety of controls required for color image processing, according to the predetermined sequence. The next description, with Figs. 70 and 72, is related to the a series of operations for color recording. This working example allows recording in single-color recording by an instruction given from the outside in addition to recording in multiple colors (blue, red and black). First, multi-color recording is described using Figs. 70 and 71. In Figs 70 and 71, the period F1 defines from the period from power-on of the main power supply to manipulation of the copy button. The period F2 shows the period for pre-rotation of the image forming unit (hereinafter called drum). The period I is a blue-development (recording) period, and the period II is a red-development period. Likewise, the period III shows a black-development period, and the period IV is a period for post-rotation. The numerals shown in these figures values for the drum counter or those for the pre-rotation counter and other counters. With the main power supply on, the main motors, like drum motor 204, rotate during a predetermined period. With the copy button mainpulated, the main motors (Fig. 70-D) rotate. If the index sensor 247 detects the V-letter index device 246 (Fig. 73) installed on the drum 11, the drum counter clears (Fig. 70-B, -C). Succeeding processing is performed based on the drum counter value. The lengths of periods I to IV (in term of time) are the same. In this example, the counter value is 778 and the drum 11 is designed to rotate once. In the pre-rotation period F2, the pre-transfer lamp is turned on from almost the middle of the position during a certain period (to the middle of the period I for blue development), and pre-processing for color development is done. In the blue- and black-development periods, the magnet 423 and development sleeve installed on the developers 123 to 125 rotate and development bias is risen synchronously with these rotation timings (Fig. 70-F to -K). The cleaning blade 127 is pressure-contacted synchronously with the rise of the drum index signal of the pre-rotation period F, and toner adhered to the drum 11 is removed (Fig. 70-L). The cleaning blade is released after a single rotation of the drum 11 (Fig. 70-M). After this toner removal, some amount of toner may be still on the drum surface, or toner may be scattered after release of the black. Accordingly, the cleaning roller has been designed to start its operation at a certain later timing from the release of the black to remove residual toner (Fig. 70-N). Right before the blue development period I, the first paper feed roller rotates to feed the recording paper to the second paper feed roller (Fig. 70-O). The first paper feed roller is installed to carry paper in the cassette. The paper carried by the first paper roller is carried by the second paper roller to the drum 11 at the timing of the final exposure process period (exposure process III, in Fig. 70-P). The paper feed operation by the first paper feed roller stops when the recording paper has reached to the temporary stop sensor installed right before the second roller. If the second paper feed roller is driven and the recording paper has passed through, the sensor output becomes zero (Fig. 70-S). Transferring is performed little later than the drive of the second paper roller. Synchronously with the transferring, the predetermined AC voltage is applied to the paper separation electrode to prevent the paper from being wrapped around the drum 11 (Fig. 70-Q). After the temporary stop sensor 227 has been become zero, the development and fixing are finished, and paper eject sensor 228 begins to examine whether the paper has been correctly ejected after fixing (Fig. 70-T). In color recording, toner density is detected every time development is done as the timing determined by the detection counter values for blue to black colors (Fig. 70-U2 to -U4). These counters have been reset according to the timing of the start of density detection patch writing. The blue counter is reset when the drum counter value is 706. If the drum counter value is 602 after resetting, toner density is detected. Likewise, the red counter is reset if the drum counter value is 707, and the black counter is also reset if the drum counter value is 707. Note that the toner density is detected by referring to a specific image region. Accordingly, patch signal for the density detection, as shown in Fig. 70-Z (for example, image signal for a 8 x 16 mm image region), is used. With this signal obtained, toner detection signal (Fig. 70-R) is provided after a lapse of a predetermined period, and the image density of the region is detected. After the copy operation start, the pre-rotation counter is cleared at the timing when the first drum index signal is entered. When the counter value is 1266, the pre-rotation processing is completed (Fig. 70-U1). With main supply power supply on, the polygon motor 934 to drive the polygon 935 is simultaneously driven, whereby the polygon 935 rotates at a constant speed (Fig. 70-V). The image data required for image recording is sent at the following timing: the vide gate becomes "1" synchronously with the blue counter, and becomes "0" at the same time as the completion of write operation (Fig. 70-W). The image data is sent to the output unit 700 only if the video gate is "1". For each development step, the vertical valid signal V-VALID made valid only in the period (until the drum counter value is 528, for a paper size of A4; see Fig. 70-Y). At the same time when the copy signal is sent from the control circuit of the output unit 700 (Fig. 70-AA), the start signal for the optical scanning is output. This optical signal is in the start state for the fall from "1" to "0" (Fig. 70-BB). Where the image reading section B is configured so that the movable mirror unit with a light source (a kind of image reading mean) is travelled, the home position signal to indicate the optical home position is sent to the output unit 700's control circuit for each development processing step (Fig. 70-CC). To perform exposure process with the home position signal, the copy R signal (Fig. 70-A) should be sent (Fig. 70-DD). The above is the description of the timing chart for multi-color recording. To record the original image in a designated color (only single color), use the timing chart as shown in Fig. 72 in which image processing is performed with respect to the designated color and image processing steps for other colors are not executed. For this reason, detailed description of the operation of single-color image processing is omitted. The processing step in Fig. 63 presents an example where image processing is done in black color (normal black/white color). The next description is related to the operation/ indicator section 202, with Fig. 74 referred to. Notation a in this figure shows a copy switch. Depressing this switch allows copy operation according to the above described sequence. Under this switch are LEDs, red one of which shows warming up and green one of which indicates ready state, when being lit. b is the indicator to show the number of copy, self diagnosis mode, or abnormal mode, and its condition. It is consists of a 7-segment LED which provides numeric representation for the above condition. c is the key pad to set the number of copies, indicate the self-diagnosis mode operation, interrupt copy operation and clear the number of copies. For example, with keys 4 and 7 depressed and the power supply switch on, the self-diagnosis mode is automatically assumed. In this mode, by entering specific numbers, the red-color developing unit motor can be automatically rotated, for example. Also in this mode, the power supply can be turned on by inputting a specific number or without depressing the key after power-off, allowing the normal mode to be set again. The normal mode enables normal copy operation. Combination of numeric keys and the P button allows data and test patterns to be printed. For example, by connecting the print controller to the second interface 42, entering data "52P" and turning the copy button, the data of the print controller data is output. Likewise, by entering data "53P" test patterns can be obtained. If the stop/clear key is depressed in the course of copy operation, for example, in the course of blue-color development with single-sheet copy in three colors, the post-rotation process proceeds after the completion of blue-color development, then returning to the initial state. This applies to the copy of multiple sheets. d shows the key to release the EE mode. Depressing the key to release the EE mode and conducting key operation shown in e and i later described enable manual adjustment of threshold. e is the keys to determine the threshold level of the overall image. Depressing the left-hand key enables a low threshold to be selected. A depression of this key allows a discrete change from the normal threshold to a next threshold within the range of 7 threshold steps. This applies to the operation of the right key but in the opposite direction. Since a portion of the document in one color (black, red or blue) is different from that in another color, a group of keys, i, is used to determine a threshold for each color. i is a group of keys used to determine a threshold for each color as already described. For example, the blue key is depressed to change a threshold for blue color. In this case, the LED of the key lights, the middle LED of the 7-level meter flashes. To obtain the desired threshold, either the left or right key of e is depressed to change the set level for each stage. Also to obtain the desired level, the blue key is depressed again and the level shown by flashing is set. In this stage, the LED in the level meter no longer flashes, and is kept lighting. This is applicable to red and black colors. Three color copy modes available: single-color mode, 2-color mode and 3-color mode which is selected by groups of keys shown by f and g. The following is the description for mainpulation of these keys. In single-color recording, the first step to do is depress the mono-key. For blue-color recording, the blue key, f, is depressed. Likewise, for black-color recording, the black key is depressed. This applied to the red-color recording. In three-color recording, the multi-key, g, is depressed. With this manipulation alone, three-color mode is assumed. By depressing the copy key, copy operation is done in the order of blue, red and black colors. If the red key is depressed in this mode, two-color mode without red color is assumed. Depressing the copy key in this mode conducts copy operation in the order of blue and black colors. Similarly, depressing the blue key assumes the mode without blue color, and depressing the copy key in this mode conducts copy operation in the order of red and black colors. Depressing the black key will conduct the copy operation in the order of red and blue colors. The key, h, is use to perform partial color conversion. Depressing this key detects the marker region on the document. The black-colored portion enclosed by the marker is recorded in the same color as the marker by the above process. In this example, the keys are shown as those to be used for partial color conversion. However, combination of these keys with a group of keys, c, enables a variety of image processing with respect to the detection region. For example, the 0XP key is used for processing with respect to a region enclosed by marker, while the 1XP is used for processing with respect to the outside the region enclosed by marker. Determining X depending on the contents of processing will allows a combination of copy processing as shown in Fig. 75. The processing shown in Fig. 75 can be effectively done by corresponding the marker color and its processing 1: 1 like, the red marker to "extraction" and the blue marker to "elimination". Such function is possible use of the color data selecting circuit 500B as shown in Fig. 44. The key, j, is used to prepare transparent document for OHP. The fixing temperature is about 200°C. The fixing temperature is thus increased to melt toner on the film, to improve smoothness and to enhance transparency. The key, k, is intended for fine-line mode. This key allows laser power to be lower than the normal use (5 mW) to 1 to 2 mW, in order to improve reproducibility of letters. This mode is effective specially if used after MTF correction has been made on extremely strong extent. The LED device, l, is used to indicate the operation state of the copying machine (jam, paper feeding, paper travel, etc.) and other feeding. The following describes combinations of key manipulation. Possible combinations are: keys of g with those of e and i, keys of g and those of d, keys of h and those of e and i, keys of h and d, or keys of j and k. Use of keys of c provides a variety of instructions for check of operation. Examples of the use are as follows. a) 6XP: Scanner check 60P + copy : Turns on the flash light (FL) and stops the scanner optical system. 1 + copy : Travels the optical system, with FL on, at a slower speed in the secondary scan direction. Note that the optical system will stop at the current position with the FL on if the copy switch is turned off. 2 + copy : The same function as the above "1 + copy", except that the optical system travels in the opposite direction. 3 + copy : Performs normal scanning successively with FL on (3-color mode). 4 + copy : Performs normal scanning successively with FL on (1-color mode). 5 + copy : Performs normal scanning successively with FL on (red-color mode). 6 + copy : Performs normal scanning successively with FL on (blue-color mode). 61P + copy : Performs the same operation as above, with FL on, the optical system stopping, and 1 to 6 + copy depressed. The operation is released if the stop/clear key is depressed. In each operation, image data is output from each circuit to check the signal level. b) 7XP: Checking the printer section 70P + copy: Rotates the polygon motor alone, with the laser on. The index signal can be checked. 1 + copy : Outputs printer controller data. 2 + copy : Outputs test pattern data. 3 + copy : Outputs patch data. 71P + copy : Recording section checking mode. 1 + copy : Charging unit on. 2 + copy : Blue-color developing unit motor on, and development bias on. 3 + copy : Red-color developing unit motor on, and development bias on. 4 + copy : Black-color developing unit motor on, and development bias on. 5 + copy : Transferring pole on. 6 + copy : Cleaning blade pressured-contact 7 + copy : Cleaning blade released 8 + copy : Voltage applied to cleaning roller 9 + copy : Separation pole on. 10 + copy : 1st paper motor on. 11 + copy : 2nd paper motor on. The above modes can be released by depressing the stop/clear key. Such self-diagnosis can be done for quick maintenance by maintenance personnel and by user should a trouble occur. As described above, the invention allows a variety of image processing after color separation but before the multivaluing process. This resolves the problem of an increase in circuit size that calls for higher cost of the apparatus. It also enables image processing such as color ghost correction and resolution correction, thus performing the desired image processing while maintaining picture quality, and attaining high-quality color recording.

Claims: An image processing apparatus for detecting a region marked with a color on a document, the color being a different color which is different from colors of an original image on said document; said apparatus comprising: means (104,105) for obtaining a color image signal having a plurality of color component signals in respect of each pixel by reading said document; color discriminating means (35); and region detecting means (500A); characterized in that: said color discriminating means (35) operates to convert said color image signal into first and second signal portions in respect of each said pixel, the first signal portion being a multiple bit density data signal common to said plurality of color component signals and representative of the original image density of that pixel, and the second signal portion being one of a plurality of predetermined color code data signals, said color discriminating means (35) operating to classify all the color information read from said original document by said obtaining means (104,105) into one of said predetermined color code data signals each representative of one of a plurality of predetermined mutually different colors; said region detecting means (500A) is adapted to detect said region by detecting said different color based on said color code data signal; and output means (600,700) responsive to the multiple bit density data signal and the color code data signals to provide signals for reproducing the processed image in desired colors and density. Image processing apparatus according to Claim 1, characterized in that said apparatus comprises image processing means (500B) for performing a different image processing operation within said region which is different from that carried out outside said region detected by said region detecting means (500A). Image processing apparatus according to Claim 2 characterized in that said means (500B) for performing image processing operates on the basis of the predetermined color code data signal obtained by discriminating the color of a coloring member which marked said document region and the output of said region detecting means (500A). Image processing apparatus according to Claim 1, characterized in that said apparatus comprises image processing means (500B) for performing a different image processing operation within said region which is different from that carried out outside said region detected by said region detecting means (500A), and recording means (700) for recording the output signal of said image processing means. Image processing apparatus according to Claim 4 characterized in that said apparatus is adapted to record the inside of said region with the predetermined color obtained by discrimination of the color of a coloring member which marked said document region. Image processing apparatus according to Claim 4 characterized in that said apparatus is adapted to record the outside of said region with the predetermined color obtained by discrimination of the color of a coloring member which marked said document region. Image processing apparatus according to Claim 4 characterized in that said apparatus is adapted not to record the output signal at pixel positions representative of the inside of said detected region. Image processing apparatus according to Claim 4 characterized in that said apparatus is adapted not to record the output signal at pixel positions representative of the outside of said detected region. Image processing apparatus according to any one of Claims 1 to 10 characterized in that said color code data signals each consist of digital bit data representative of that said predetermined color. Image processing apparatus according to any one of Claims 1 to 11 characterized by further including processing means (450) which operates to correct resolution of the image on the basis of said multiple bit density data signal before subsequent multi-value coding (600) of the density data signal in respect of each said pixel.

Inventors: ABE YOSHINORI, HASEBE TAKASHI, KATO HIROSHI, KIMOTO TETSUO, MATSUNAWA MASAHIKO, YAMAMOTO HIROYUKI, ABE, YOSHINORI, HASEBE, TAKASHI, KATO, HIROSHI, KIMOTO, TETSUO, MATSUNAWA, MASAHIKO, YAMAMOTO, HIROYUKI, ABE, YOSHINORI KONICA CORPORATION, HASEBE, TAKASHI KONICA CORPORATION, KATO, HIROSHI KONICA CORPORATION, KIMOTO, TETSUO KONICA CORPORATION, MATSUNAWA, MASAHIKO KONICA CORPORATION, YAMAMOTO, HIROYUKI KONICA CORPORATION
Applicants: KONISHIROKU PHOTO IND, KONICA CORPORATION
Application year: 1988
Main classification: H04N1
IPC codes: H04N1