Patent Publication Number: US-2016248928-A1

Title: Image processing apparatus, control method, and computer-readable medium

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image processing apparatus, control method, and computer-readable medium for generating a print image by compositing an image such as a copy-forgery-inhibited pattern image. 
     2. Description of the Related Art 
     There has conventionally been known a special printing method (to be referred to as “copy-forgery-inhibited-pattern printing”) of making a warning message surface when a printed material is copied, in order to suppress illicit copying of a confidential document or the like. In copy-forgery-inhibited-pattern printing, a part that appears upon copying is called a “latent image”, and a part that disappears or fades upon copying is called a “background image”. Printing is done by compositing a copy-forgery-inhibited pattern image in which a copy-forgery-inhibited pattern formed from a latent image and background image is embedded, and an image to be printed. For example, when the latent image or background image has the shape of a warning message such as “COPY PROTECTED” or “COPY”, the warning message is embedded as a copy-forgery-inhibited pattern in the copy-forgery-inhibited pattern image. In a copy-forgery-inhibited pattern-embedded printed material, the background image camouflages the latent image, so it is difficult for the user to recognize the embedded copy-forgery-inhibited pattern when he checks the printed material. However, once the copy-forgery-inhibited pattern-embedded printed material is copied, the background image disappears, the latent image appears, and the warning message surfaces as the copy-forgery-inhibited pattern in the copy. By printing a copy-forgery-inhibited pattern which surfaces upon copying, copy-forgery-inhibited-pattern printing implements a copy deterrent function. 
     In copy-forgery-inhibited-pattern printing, a copy-forgery-inhibited pattern image is composited in an image to be printed. In some cases, the amount of color material (to be referred to as an “amount of applied toner”) applied per unit area exceeds a limit value (to be referred to as a “maximum amount of applied toner”) which is set in advance in an image processing apparatus. That is, even if an image to be printed is generated so as not to exceed the maximum amount of applied toner, the amount of applied toner may still exceed said maximum amount because a copy-forgery-inhibited pattern image is added later. Printing with more than the maximum amount of applied toner may cause a fixing error and damage the engine. To prevent this, the entire image signal level after composition needs to be decreased to a predetermined value. This processing method can be, for example, a method disclosed in Japanese Patent Laid-Open No. 2009-27225. More specifically, a print image undergoes density correction, and the corrected print image and a copy-forgery-inhibited pattern image are composited. This can prevent degradation of the copy deterrent function of the copy-forgery-inhibited pattern image, and achieve density correction. 
     However, the technique disclosed in Japanese Patent Laid-Open No. 2009-27225 suppresses consumption of print consumables in copy-forgery-inhibited-pattern printing, and density correction is always done for a print image. Even if the amount of applied toner does not exceed the maximum amount, density correction is executed, resulting in poor quality in a copy-forgery-inhibited pattern-embedded printed material. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve the above problems, and has as its object to prevent a fixing error generated when the amount of applied toner exceeds the maximum amount set in an image processing apparatus, and prevent unwanted degradation of the image quality of a printed material in composition printing such as copy-forgery-inhibited-pattern printing. 
     According to one aspect of the present invention, there is provided an image processing apparatus which generates copy-forgery-inhibited pattern print image data by compositing print image data and copy-forgery-inhibited pattern image data, the apparatus comprising: an applied amount calculation unit which calculates an amount of applied toner of the print image data and an amount of applied toner of the copy-forgery-inhibited pattern image data; a determination unit which determines, based on the amounts of applied toner calculated by the applied amount calculation unit, whether the sum of the amounts of applied toner of the print image data and the copy-forgery-inhibited image exceeds a predetermined amount of applied toner; an applied amount control unit which, in a case where the determination unit determines that the sum of the amounts of applied toner exceeds the predetermined amount of applied toner, restricts the amount of applied toner of the print image data to prevent the sum of the amounts of applied toner from exceeding the predetermined amount of applied toner; and a composition unit which composites the print image data whose amount of applied toner is restricted by the applied amount control unit, and the copy-forgery-inhibited pattern image data, generating the copy-forgery-inhibited pattern print image data. 
     According to another aspect of the present invention, there is provided an image processing apparatus which generates composite print image data from print image data and composite image data to be composited in the print image data, the apparatus comprising: a ratio calculation unit which calculates a ratio at which the composite image data occupies the print image data; a comparison unit which compares, with a threshold, the ratio at which the composite image data occupies the print image data and which is calculated by the ratio calculation unit; and an applied amount control composition unit which is executed in a case where the ratio at which the composite image data occupies the print image data is not lower than the threshold as a result of comparison by the comparison unit, the applied amount control composition unit including: an applied amount calculation unit which calculates an amount of applied toner of the print image data and an amount of applied toner of the composite image data; a determination unit which determines, based on the amounts of applied toner calculated by the applied amount calculation unit, whether a sum of the amounts of applied toner exceeds a predetermined amount of applied toner in a case where the print image data and the composite image data are composited; an applied amount control unit which, in a case where the determination unit determines that the sum of the amounts of applied toner exceeds the predetermined amount of applied toner, restricts the amount of applied toner of the print image data to prevent an amount of applied toner after composition from exceeding the predetermined amount of applied toner; and a composition unit which composites the print image data whose amount of applied toner is restricted by the applied amount control unit, and the composite image data, generating the composite print image data. 
     According to still another aspect of the present invention, there is provided an image processing method of generating copy-forgery-inhibited pattern print image data by compositing print image data and copy-forgery-inhibited pattern image data, the method comprising: an applied amount calculation step of calculating an amount of applied toner of the print image data and an amount of applied toner of the copy-forgery-inhibited pattern image data; a determination step of determining, based on the amounts of applied toner calculated in the applied amount calculation step, whether the sum of the amounts of applied toner of the print image data and the copy-forgery-inhibited image exceeds a predetermined amount of applied toner; an applied amount control step of, in a case where the sum of the amounts of applied toner is determined in the determination step to exceed the predetermined amount of applied toner, restricting the amount of applied toner of the print image data to prevent the sum of the amounts of applied toner from exceeding the predetermined amount of applied toner; and a composition step of compositing the print image data whose amount of applied toner is restricted in the applied amount control step, and the copy-forgery-inhibited pattern image data to generate the copy-forgery-inhibited pattern print image data. 
     According to yet another aspect of the present invention, there is provided a computer-readable medium storing a program for causing a computer to function as an applied amount calculation unit which calculates an amount of applied toner of print image data and an amount of applied toner of copy-forgery-inhibited pattern image data, a determination unit which determines, based on the amounts of applied toner calculated by the applied amount calculation unit, whether the sum of the amounts of applied toner of the print image data and the copy-forgery-inhibited image exceeds a predetermined amount of applied toner, an applied amount control unit which, in a case where the determination unit determines that the sum of the amounts of applied toner exceeds the predetermined amount of applied toner, restricts the amount of applied toner of the print image data to prevent the sum of the amounts of applied toner from exceeding the predetermined amount of applied toner, and a composition unit which composites the print image data whose amount of applied toner is restricted by the applied amount control unit, and the copy-forgery-inhibited pattern image data, generating copy-forgery-inhibited pattern print image data. 
     According to yet still another aspect of the present invention, there is provided a computer-readable medium storing a program for causing a computer to function as a ratio calculation unit which calculates a ratio at which composite image data occupies print image data, a comparison unit which compares, with a threshold, the ratio at which the composite image data occupies the print image data and which is calculated by the ratio calculation unit, and an applied amount control composition unit which is executed in a case where the ratio at which the composite image data occupies the print image data is not lower than the threshold as a result of comparison by the comparison unit, wherein the applied amount control composition unit functions as an applied amount calculation unit which calculates an amount of applied toner of the print image data and an amount of applied toner of the composite image data, a determination unit which determines, based on the amounts of applied toner calculated by the applied amount calculation unit, whether a sum of the amounts of applied toner exceeds a predetermined amount of applied toner in a case where the print image data and the composite image data are composited, an applied amount control unit which, in a case where the determination unit determines that the sum of the amounts of applied toner exceeds the predetermined amount of applied toner, restricts the amount of applied toner of the print image data to prevent an amount of applied toner after composition from exceeding the predetermined amount of applied toner; and a composition unit which composites the print image data whose amount of applied toner is restricted by the applied amount control unit, and the composite image data, generating the composite print image data. 
     According to yet still another aspect of the present invention, there is provided an image processing method of generating composite print image data from print image data and composite image data to be composited in the print image data, the method comprising: a ratio calculation step of calculating a ratio at which the composite image data occupies the print image data; a comparison step of comparing, with a threshold, the ratio at which the composite image data occupies the print image data and which is calculated in the ratio calculation step; and an applied amount control composition step which is executed in a case where the ratio at which the composite image data occupies the print image data is not lower than the threshold as a result of comparison in the comparison step, the applied amount control composition step including: an applied amount calculation step of calculating an amount of applied toner of the print image data and an amount of applied toner of the composite image data; a determination step of determining, based on the amounts of applied toner calculated in the applied amount calculation step, whether a sum of the amounts of applied toner exceeds a predetermined amount of applied toner in a case where the print image data and the composite image data are composited; an applied amount control step of, in a case where the sum of the amounts of applied toner is determined in the determination step to exceed the predetermined amount of applied toner, restricting the amount of applied toner of the print image data to prevent an amount of applied toner after composition from exceeding the predetermined amount of applied toner; and a composition step of compositing the print image data whose amount of applied toner is restricted in the applied amount control step, and the composite image data, generating the composite print image data. 
     The present invention can prevent a fixing error generated when the amount of applied toner exceeds the maximum amount set in an image processing apparatus, and prevent unwanted degradation of the image quality of printed material in composition printing wherein image data such as a copy-forgery-inhibited pattern image is added. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a system block diagram for explaining the arrangement of an image processing apparatus according to an embodiment; 
         FIG. 2  is a block diagram for explaining the arrangement of an image processing unit according to the first embodiment; 
         FIG. 3  is a flowchart of exemplary processing according to the first embodiment; 
         FIG. 4  is a schematic exemplary view according to the first embodiment; 
         FIG. 5  is a block diagram for explaining the arrangement of an image processing unit according to the second embodiment; 
         FIG. 6  is a flowchart of exemplary processing according to the second embodiment; 
         FIG. 7  is a schematic exemplary view according to the second embodiment; 
         FIGS. 8A and 8B  are views for explaining print environment setting items in copy-forgery-inhibited-pattern printing according to the embodiment; 
         FIG. 9  is a block diagram for explaining the arrangement of an image processing unit according to the third embodiment; 
         FIG. 10  is a flowchart of exemplary processing according to the third embodiment; 
         FIG. 11  is a schematic exemplary view according to the third embodiment; and 
         FIG. 12  is a view for explaining an LUT generation unit  404  according to the embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiments of the present invention will now be described with reference to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a system block diagram that explains the basic arrangement of an image processing apparatus according to the present invention. An apparatus, to which the present invention is applied, copes with an electrophotographic color or monochrome image processing apparatus using toner, such as a digital electrophotographic copying machine, laser printer, or facsimile apparatus. The image processing apparatus according to the present invention includes a CPU (Central Processing Unit)  101 , ROM (Read Only Memory)  102 , RAM (Random Access Memory)  103 , HDD  104 , display unit  105 , operation unit  106 , engine I/F  107 , network I/F  108 , scanner I/F  109 , image processing unit  110 , and system bus  111 . 
     This arrangement will be described in detail. The CPU  101  controls the overall apparatus, and performs arithmetic processing and the like. The CPU  101  executes each processing in  FIG. 2  (to be described later) based on a program stored in the ROM  102 . The ROM  102  is a storage area for a system boot program, a program for controlling a printer engine, text data, character code information, and the like. The RAM  103  is a data storage area free from usage restriction, and is used when loading and executing programs and data for various processes. The RAM  103  is also used as a data storage area for a received image file. The HDD  104  is formed from, for example, a hard disk. The HDD  104  stores programs, information files, print images, and the like, and is used as a work area. 
     The display unit  105  provides a display using liquid crystal or the like, and is used to display an apparatus setting state, current processing in the apparatus, an error state, and the like. The operation unit  106  is used to change and reset settings. The engine I/F  107  is used to exchange commands and the like for actually controlling the printer engine. The network I/F  108  connects the apparatus to a network. The scanner I/F  109  is connected to a reader (for example, scanner unit) for reading a print image via a parallel (or serial) port. The image processing unit  110  performs desired image processing for image data received via the network I/F  108  or scanner I/F  109 . Details of the image processing unit  110  will be described with reference to  FIGS. 2 and 5 . The system bus  111  connects these building components, and serves as a data path between them. 
       FIG. 2  is a block diagram for explaining the arrangement of the image processing unit  110  in the first embodiment of the present invention. An input print image is received via the network I/F  108  using a driver or the like on the host computer, or via the scanner I/F  109  using the scanner unit or the like. The RAM  103  holds the input print image. Based on an instruction set by the user using the display unit  105  and operation unit  106 , a copy-forgery-inhibited-pattern printing determination unit  201  determines whether to perform copy-forgery-inhibited-pattern printing.  FIG. 8A  exemplifies a screen for designating, for example, the shape of a warning message such as “COPY PROTECTED” or “COPY” using the display unit  105  and operation unit  106 .  FIG. 8B  exemplifies a screen for designating the print size, print color, and the like. Note that the screen for accepting an instruction from the user is not limited to them, and may include a component or function not shown here. Image data to be printed will be called a print image (or print image data), and an image to be printed as the background image of the print image will be called a copy-forgery-inhibited pattern image (or copy-forgery-inhibited pattern image data). An image generated by compositing the print image and copy-forgery-inhibited pattern image will be called a copy-forgery-inhibited pattern print image (or copy-forgery-inhibited pattern print image data). 
     A color conversion unit  202  converts a print image into data suited to the image processing apparatus. An applied amount calculation unit  203  calculates the amount of applied toner of the print image, and that of applied toner of a copy-forgery-inhibited pattern image designated via the display unit  105  or operation unit  106 . A determination unit  204  calculates the amount of applied toner upon copy-forgery-inhibited-pattern composition, based on the amounts of applied toner of the print image and copy-forgery-inhibited pattern image that are calculated by the applied amount calculation unit  203 . The determination unit  204  determines whether the calculated amount of applied toner exceeds the maximum amount of applied toner set in the image processing apparatus. An applied amount control unit  205  controls the amount of applied toner of the print image based on the amount of applied toner of the copy-forgery-inhibited pattern image that is calculated by the applied amount calculation unit  203 . An image forming unit  206  performs halftoning for the print image. A composition unit  207  composites the print image and copy-forgery-inhibited pattern image. After that, the composition unit  207  sends and outputs the copy-forgery-inhibited pattern print image data to the image processing apparatus via the engine I/F  107 . 
       FIG. 3  is a flowchart of exemplary processing executed by the image processing apparatus in the first embodiment.  FIG. 4  is a schematic view of the processing. In S 11 , by referring to copy-forgery-inhibited-pattern printing setting information, the copy-forgery-inhibited-pattern printing determination unit  201  determines whether to perform copy-forgery-inhibited-pattern printing for a print image received via the network I/F  108  or scanner I/F  109 . If the copy-forgery-inhibited-pattern printing determination unit  201  determines to perform copy-forgery-inhibited-pattern printing (YES in S 11 ), the process advances to S 12 . If the copy-forgery-inhibited-pattern printing determination unit  201  determines not to perform copy-forgery-inhibited-pattern printing (NO in S 11 ), the process advances to S 19 , and the print image is normally output after undergoing color conversion processing and image forming processing without applying the present invention. The setting information used in this step is a set value input from the operation unit  106  using the display unit  105  in the image processing apparatus, or a set value input from a driver UI on the host computer. For example, as shown in  FIGS. 8A and 8B , print environment setting items in copy-forgery-inhibited pattern setting are prepared and allow the user to freely set the stamp type, print size, print color, and the like using the display unit  105  and operation unit  106  in the image processing apparatus, and the driver UI. As the instruction, a set value may always be held regardless of the execution timing, or interactively acquired when the user presses the print button. The RAM  103  in  FIG. 1  holds a received image file. 
     In S 12 , the color conversion unit  202  converts the image data into data (for example, CMYK data) suitable for the image processing apparatus based on a color conversion table. The color conversion table is, for example, a 3D LUT (3D Look Up Table) that is a typical color conversion processing method. The color conversion table is a search table indicating a correspondence for converting RGB data into CMYK data, and is formed from N×N×N matrix points. In principle, by setting the matrix interval sufficiently narrow, color conversion can be achieved with high precision. In practice, however, it is rare that a point subjected to color conversion matches a matrix point in terms of the memory capacity, processing speed, and the like. Thus, CMYK data is obtained by three-dimensional interpolation processing. 
     In S 13 , the applied amount calculation unit  203  calculates the amount of applied toner of the print image, and that of applied toner of a copy-forgery-inhibited pattern image designated via the display unit  105  or operation unit  106 . In the calculation method for the print image, the amounts of applied toner corresponding to the signal values of respective colors (for example, C, M, Y, are K) of image data (print image or copy-forgery-inhibited pattern image) are stored in advance in the form of a 1D LUT (1D Look Up Table). In an actual operation, the amounts of applied toner of the respective colors of the image data are added while referring to the 1D LUT. A maximum value among all pixels is held as the amount of applied toner of print image data. When a copy-forgery-inhibited pattern image is added to only a partial region of the print image, calculation of the amount of applied toner of the print image is restricted to this region to obtain a maximum value, instead of obtaining a maximum value among all pixels. A limit value (maximum amount of applied toner) set in advance in the image processing apparatus may be set as the amount of applied toner of the print image. 
     For the copy-forgery-inhibited pattern image, the color which forms the image changes depending on the print color setting of the print environment setting item, and needs to be obtained while referring to the set value. In copy-forgery-inhibited-pattern printing, a part which appears upon copying is called a “latent image”, and a part which disappears or fades upon copying is called a “background image”. The amounts of applied toner of the latent image and background image are calculated, obtaining the amount of applied toner of the copy-forgery-inhibited pattern image. A practical method is as follows. 
     Letting H be the amount of applied toner of the copy-forgery-inhibited pattern image, H_sdot(sdot) be the amount of applied toner of the background image dot of the copy-forgery-inhibited pattern, and H_ldot(ldot) be the amount of applied toner of the latent image dot of the copy-forgery-inhibited pattern, H is calculated by 
         H =( H _ s dot( s dot)+ H _ l dot( l dot))/2  (1)
 
     The amount of applied toner of the background image dot of the copy-forgery-inhibited pattern, and that of applied toner of the latent image dot of the copy-forgery-inhibited pattern should originally become equal to each other by calibration or the like. However, the above calculation considers a case in which these amounts of applied toner are different due to instability of the image processing apparatus. 
     sdot and ldot are density value of background part and density value of latent image part, respectively, in copy-forgery-inhibited pattern image input from UI shown  FIG. 8A . The applied amount H_sdot(sdot) of the background image dot of the copy-forgery-inhibited pattern, and the applied amount H_ldot(ldot) of the latent image dot of the copy-forgery-inhibited pattern are calculated using an LUT which is prepared in advance to convert a density value into the amount of applied toner. The LUT for use is prepared for each copy-forgery-inhibited pattern color, and an LUT needs to be selected in accordance with the copy-forgery-inhibited pattern color. When calculating the amount of applied toner of the copy-forgery-inhibited pattern image in accordance with the dot density, it may be weighted (by the ratio): 
         H =( H _ s dot( s dot)*ratio+ H _ l dot( l dot)*ratio)/2  (2)
 
     In the first embodiment, the copy-forgery-inhibited pattern image is recorded in advance in the ROM  102 . Thus, the amount of applied toner of the copy-forgery-inhibited pattern image may be calculated in advance for each set value (the print size and print color of copy-forgery-inhibited pattern input from UI shown  FIG. 8B ) and held in the ROM  102 . 
     In S 14 , the determination unit  204  calculates the amount of applied toner upon copy-forgery-inhibited-pattern composition, based on the amounts of applied toner of the print image and copy-forgery-inhibited pattern image that have been calculated by the applied amount calculation unit  203 . That is, the amount of applied toner upon copy-forgery-inhibited-pattern composition is the sum of the amounts of applied toner of the print image and copy-forgery-inhibited pattern image. As described in S 13 , the amount of applied toner of the print image is a maximum value among the sum of the amounts of applied toner of the respective colors (C, M, Y, K) of each pixel of the print image in all pixels of the image data. Then, the determination unit  204  determines whether the sum of the amounts of applied toner of the print image and copy-forgery-inhibited pattern image exceeds the maximum amount of applied toner (limit value) set in the image processing apparatus. If the sum does not exceed the maximum amount of applied toner, the process advances to S 16  without performing a process in S 15 . Note that the sum of the amount of applied toner of each pixel of the print image and the copy-forgery-inhibited pattern image is calculated, and each pixel can be determined whether to control the amount of applied toner to the print image according to the sum of the amount of applied toner of each pixel. 
     In S 15 , the applied amount control unit  205  reduces the amount of applied toner of the print image by the increase of the amount of applied toner of the copy-forgery-inhibited pattern image, based on the amount of applied toner of the copy-forgery-inhibited pattern image that has been calculated by the applied amount calculation unit  203 . The increase of the amount of applied toner of the copy-forgery-inhibited pattern image is a value obtained by subtracting the maximum amount of applied toner from the sum of the amount of applied toner of the print image (a maximum value among the sum of the amounts of applied toner in all pixels of the image data) and the amount of applied toner of the copy-forgery-inhibited pattern image. 
     In copy-forgery-inhibited-pattern printing, the amount of applied toner is increased by printing a copy-forgery-inhibited pattern image. Thus, the amount of applied toner for printing a print image is decreased by that of applied toner necessary to print a copy-forgery-inhibited pattern image. When the copy-forgery-inhibited pattern image is formed in only a specific color (for example, cyan), the amount of applied toner may be decreased for only the color which forms the copy-forgery-inhibited pattern image, instead of decreasing the amount of applied toner for all the colors of the print image. When the copy-forgery-inhibited pattern image is added to only a partial region of the print image, the amount of applied toner of the print image is reduced in only this region. Although not described in detail, a variety of methods are available for processing of reducing the amount of applied toner. For example, the signal values of respective colors (for example, C, M, Y, and K) of image data (print image in this case) may be decreased uniformly, or UCR (Under Color Removal) processing may be executed to replace a predetermined number of CMY signals with K signals. 
     In S 16 , the image forming unit  206  executes halftoning for the print image and copy-forgery-inhibited pattern image. In S 17 , the composition unit  207  composites the print image and copy-forgery-inhibited pattern image. As the composition method, the print image is deleted for only a color (for example, cyan) which forms the copy-forgery-inhibited pattern image, in only a region where the copy-forgery-inhibited pattern image is added. Then, the copy-forgery-inhibited pattern image is added, generating a copy-forgery-inhibited pattern print image. In S 18 , the composition unit  207  sends and outputs, to the engine via the engine I/F  107 , the copy-forgery-inhibited pattern print image created by the composition unit  207 . 
     As described above, as an effect of the first embodiment, a fixing error generated when the amount of applied toner exceeds the maximum amount can be prevented in copy-forgery-inhibited-pattern printing. Only when the amount of applied toner exceeds the maximum amount, the applied amount is controlled. Even if the amount of applied toner of a print image is controlled, the amount of applied toner is compensated for by compositing a copy-forgery-inhibited pattern image. This can prevent degradation of the image quality of a printed material. 
     Second Embodiment 
     The first embodiment has described a composition method of, when the amount of applied toner necessary for copy-forgery-inhibited-pattern printing exceeds the maximum amount set in the image processing apparatus, calculating the value of the amount of applied toner of a copy-forgery-inhibited pattern image, and controlling the amount of applied toner of a print image based on the calculated value. As an application of the first embodiment, the second embodiment will explain a method of preventing degradation of the image quality of a printed material and preventing a decrease in performance by switching between the composition method of the first embodiment and a well-known composition method in accordance with the ratio at which a composite image such as a copy-forgery-inhibited pattern image or numbering image occupies a print image. An image to be printed will be called a print image, an image to be composited in the print image will be called a composite image (or composite image data), and an image generated by compositing the print image and composite image will be called a composite print image (or composite print image data). Assume that the composite image includes a copy-forgery-inhibited pattern image described in the first embodiment. 
       FIG. 5  is a block diagram for explaining the arrangement of an image processing unit  110  in the second embodiment of the present invention. An input print image is received via a network I/F  108  using a driver or the like on the host computer, or via a scanner I/F  109  using a scanner unit or the like. A RAM  103  holds the input print image. Based on an instruction set using a display unit  105  and operation unit  106 , a composition printing determination unit  301  determines whether to perform composition printing. A color conversion unit  302  converts a print image into data suited to an image processing apparatus. A ratio calculation unit  303  calculates the ratio at which a composite image such as a copy-forgery-inhibited pattern image or numbering image occupies the size of the print image. The calculation method is arbitrary, and the ratio may be calculated based on, for example, the number of pixels. The ratio calculation unit  303  compares the calculated ratio with a preset threshold to determine whether the calculated ratio is greater than or equal to the threshold. If the ratio calculation unit  303  determines that the calculated ratio is lower than the threshold, a replace composition unit  304  performs halftoning for the print image and composite image, and executes replace composition. Thereafter, the replace composition unit  304  sends and outputs the resultant image to the image processing apparatus via an engine I/F  107 . If the ratio calculation unit  303  determines that the calculated ratio is greater than or equal to the threshold, an applied amount control composition unit  305  controls and composites the amounts of applied toner of the print image and composite image. Applied amount control composition is the method described in the first embodiment. The internal arrangement of the applied amount control composition unit  305  includes the same processes as those of the applied amount calculation unit  203  to composition unit  207  in the first embodiment. The applied amount control composition unit  305  sends and outputs the resultant image to the image processing apparatus via the engine I/F  107 . 
       FIG. 6  is a flowchart of exemplary processing executed by the image processing apparatus in the second embodiment.  FIG. 7  is a schematic view of the processing. In S 21 , by referring to composition printing setting information, the composition printing determination unit  301  determines whether to perform composition printing for a print image received via the network I/F  108  or scanner I/F  109 . If the composition printing determination unit  301  determines not to perform composition printing (NO in S 21 ), the process advances to S 28 , and the print image is output after undergoing color conversion processing and image forming processing without applying the present invention. The setting information used in this step is a set value input from the operation unit  106  using the display unit  105  in the image processing apparatus, or a set value input from a driver UI on the host computer. As the instruction, a set value may always be held regardless of the execution timing, or interactively acquired when the user presses the print button. The RAM  103  in  FIG. 1  holds a received image file. 
     In S 22 , the color conversion unit  302  converts the image data into data (for example, CMYK data) suitable for the image processing apparatus based on a color conversion table. In S 23 , the ratio calculation unit  303  calculates the ratio at which the composite image occupies the print image. In S 24 , the ratio calculation unit  303  compares the calculated ratio with a preset threshold, and determines, based on the comparison result, whether the calculated ratio is greater than or equal to the threshold. The ratio at which the composite image occupies the print image may be calculated in advance in accordance with the type (copy-forgery-inhibited pattern, numbering, or information embedding) and setting of the composition method, and held in a ROM  102 . Accordingly, a selection composition unit is implemented to select a composition unit to be applied to the image data. If the ratio calculation unit  303  determines in S 24  that the calculated ratio is lower than the threshold, the replace composition unit  304  executes halftoning for the print image and composite image, and performs replace composition in S 25 . Assume that the replace composition method is a known method. In replace composition, all the colors (for example, C, M, Y, and K) of a print image are deleted and replaced with the colors (C, M, Y, K, R, G, and B) of a composite image in a region where the composite image is added. When composition is done by software processing without using hardware, the processing time may become long. However, the print image is replaced with the composite image, so whether the amount of applied toner exceeds the maximum amount need not be cared. 
     If the ratio calculation unit  303  determines in S 24  that the calculated ratio is greater than or equal to the threshold, the applied amount control composition unit  305  performs applied amount control composition in S 26 . Applied amount control composition is the method described in the first embodiment. More specifically, the amounts of applied toner of a print image and composite image are calculated and added, calculating the amount of applied toner of the composite print image. Then, it is determined whether the calculated amount of applied toner exceeds the maximum amount of applied toner set in the image processing apparatus. If the calculated amount of applied toner exceeds the maximum amount, the amount of applied toner of the print image is reduced by the increase of the amount of applied toner of the composite image, based on the calculated amount of applied toner of the composite image. After that, halftoning is executed for the print image and composite image, compositing them. In applied amount control composition, a composite image is composited over a print image. Hence, even if a print image is generated not to exceed the maximum amount of applied toner, the amount of applied toner may exceed the maximum amount by the amount of applied toner of a composite image added later. In this case, the above-described processing is done to reduce the amount of applied toner of the print image. As for the processing time, for example, when the amount of applied toner is controlled by hardware, the processing time is considered to become shorter than that in replace composition. This is because it suffices to perform control of the amount of applied toner and composition only for a specific color which forms a composite image. In S 27 , the replace composition unit  304  or applied amount control composition unit  305  sends and outputs the composite print image created in S 25  or S 26  to the engine via the engine I/F  107 . 
     As described above, in the second embodiment, replace composition is selected when the ratio at which the composite image occupies the print image is low (lower than the threshold), and applied amount control composition is selected when the ratio is high. This is because the applied amount is controlled in the entire region of the print image, and if the ratio at which the composite image occupies the print image is low, the amount of applied toner is not fully compensated for even after composition, and the image greatly degrades. In contrast, when the ratio at which the composite image occupies the print image is high (greater than or equal to the threshold), the amount of applied toner is compensated for by composition in a wide region, so image degradation hardly stands out. As for the performance, when the ratio at which the composite image occupies the print image is high, executing replace composition for all the colors (for example, C, M, Y, and K) of the print image may prolong the processing time. However, when the ratio at which the composite image occupies the print image is low, the processing time remains short even in replace composition. By switching the composition method depending on the ratio at which the composite image occupies the print image, a fixing error generated when the amount of applied toner exceeds the maximum amount can be prevented. In addition, degradation of the image quality of a printed material and a decrease in performance can be prevented. 
     Third Embodiment 
     In S 15  of  FIG. 3 , the applied amount control unit  205  reduces the amount of applied toner of a print image by the increase of the amount of applied toner of a copy-forgery-inhibited pattern image, based on the amount of applied toner of the copy-forgery-inhibited pattern image that is calculated by the applied amount calculation unit  203 . The increase of the amount of applied toner of the copy-forgery-inhibited pattern image is a value obtained by subtracting the maximum amount of applied toner from the sum of the amounts of applied toner of the print image and copy-forgery-inhibited pattern image. 
     The first and second embodiments have described a composition method of, when the amount of applied toner necessary for copy-forgery-inhibited-pattern printing exceeds the maximum amount set in the image processing apparatus, calculating the value of the amount of applied toner of a copy-forgery-inhibited pattern image, and controlling the amount of applied toner of a print image based on the calculated value. In the method described in the first and second embodiments, although the copy-forgery-inhibited pattern image is formed from only a specific color (for example, cyan) and added, all C, M, Y, and K colors are subtracted from the print image. This can prevent the amount of applied toner from exceeding the maximum amount upon composition. However, the color balance is lost, and the copy-forgery-inhibited pattern print image is output in color tint different from the original one of the print image. The third embodiment pays attention to this problem. When the copy-forgery-inhibited pattern image is formed from only a specific color (for example, cyan), γ (gamma) correction processing is performed for only the specific color (for example, cyan) in the print image, and only the specific color after the gamma correction processing is subtracted from the print image. This can prevent color imbalance, and the copy-forgery-inhibited pattern print image can be output in almost the same color tint as that of the print image. However, only this processing cannot prevent the amount of applied toner from exceeding the maximum amount when the copy-forgery-inhibited pattern image is formed from, for example, only cyan and added, and the print image does not contain the amount of cyan which can compensate for the subtracted amount. In the third embodiment, therefore, the same processing as that in the first and second embodiments is executed after processing for a specific color. A detailed method will be described below. 
       FIG. 9  is a block diagram for explaining the arrangement of an image processing unit  110  in the third embodiment of the present invention. An input print image is received via a network I/F  108  using a driver or the like on the host computer, or via a scanner I/F  109  using a scanner unit or the like. A RAM  103  holds the input print image. 
     Similar to the first embodiment, based on an instruction set by the user using a display unit  105  and operation unit  106 , a copy-forgery-inhibited-pattern printing determination unit  401  determines whether to perform copy-forgery-inhibited-pattern printing. A color conversion unit  402  converts a print image into data suited to an image processing apparatus. An applied amount calculation unit  403  calculates the amount of applied toner of the print image, and that of applied toner of a copy-forgery-inhibited pattern image designated via the display unit  105  or operation unit  106 . An LUT generation unit  404  generates an LUT for performing gamma correction processing based on the result of the applied amount calculation unit  403  for a specific color designated as the color of the copy-forgery-inhibited pattern image in copy-forgery-inhibited-pattern printing. A GM processing unit  405  executes gamma correction processing for the specific color of the print image, based on the LUT generated by the LUT generation unit  404 . A determination unit  406  calculates the amount of applied toner upon copy-forgery-inhibited-pattern composition, based on the amount of applied toner of the print image having undergone gamma correction processing by the GM processing unit  405 , and the amount of applied toner of the copy-forgery-inhibited pattern image that are calculated by the applied amount calculation unit  403 . The determination unit  406  determines whether the calculated amount of applied toner exceeds the maximum amount of applied toner set in the image processing apparatus. An applied amount control unit  407  controls the amount of applied toner of the print image based on the value calculated by the applied amount calculation unit  403 . An image forming unit  408  performs halftoning for the print image. A composition unit  409  composites the print image and copy-forgery-inhibited pattern image. Thereafter, the composition unit  409  sends and outputs the copy-forgery-inhibited pattern print image data to the image processing apparatus via an engine I/F  107 . 
       FIG. 10  is a flowchart of exemplary processing executed by the image processing apparatus in the third embodiment.  FIG. 11  is a schematic view of the processing. S 31  to S 33 , S 36 , and S 38  to S 41  are the same as S 11  to S 14 , and S 16  to S 19  in the exemplary flowchart of the first embodiment shown in  FIG. 3 . Thus, only a difference will be explained. 
     In S 34 , the LUT generation unit  404  generates an LUT for a specific color (cyan in the schematic view of  FIG. 11 ) designated as the color of a copy-forgery-inhibited pattern image in copy-forgery-inhibited-pattern printing, based on the amount of applied toner of the copy-forgery-inhibited pattern image that is calculated by the applied amount calculation unit  403 . The generated LUT is used to perform gamma correction processing for only the specific color of a print image so as to reduce the amount of applied toner by the increase of the amount of applied toner of the copy-forgery-inhibited pattern image. Note that the increase of the amount of applied toner of the copy-forgery-inhibited pattern image is the amount of applied toner of the copy-forgery-inhibited pattern image. The amount of applied toner is decreased uniformly even in an image region (density region) where the amount of applied toner does not exceed the maximum amount regardless of the copy-forgery-inhibited pattern image. In other words, the amount of applied toner is decreased uniformly by the amount of applied toner of the copy-forgery-inhibited pattern image in the entire image region for the specific color of the print image. A concrete LUT generation method will be explained with reference to  FIG. 12 . 
     First, the amount of applied toner of the copy-forgery-inhibited pattern image (cyan) that is calculated by the applied amount calculation unit  403  is converted into the density (the amount of applied toner is that of color material per unit area and thus can be converted into the density). Assume that the cyan density of the copy-forgery-inhibited pattern image is 0.07. Therefore, the LUT is generated to reduce the cyan color of the print image in the entire image uniformly by the increase “0.07” of the cyan density that is caused by the copy-forgery-inhibited pattern image. For example, when an input signal (10 bits) “1023” is sent to the image processing apparatus via the engine I/F  107 , printing is done at the cyan density of 1.36 for the print image. To suppress the cyan density of the print image to 1.29 (signal value of 970) in advance, an LUT for converting the input value “1023” into an output value “970” is generated. When the cyan density of the print image is lower than 0.07 from the beginning, the density is converted into 0 (signal value is also 0). In this processing, the original density value PRINT_DEN of the print image, the target density value TARGET_DEN of the print image, the density value JIMON_DEN of the copy-forgery-inhibited pattern image, the input value INPUT of the LUT, and the output value OUTPUT of the LUT are defined as 
       TARGET_DEN=PRINT_DEN−JIMON_DEN OUTPUT=INPUT corresponding to TARGET_DEN  (3)
 
     Note that the LUT is arbitrarily a 1D or 3D LUT. The amount of applied toner may be reduced not using the LUT but using a conversion value based on simple offset calculation or the like. 
     In S 35 , the GM processing unit  405  performs gamma correction processing for the specific color designated in copy-forgery-inhibited-pattern printing of the print image by using the LUT generated by the LUT generation unit  404 . In this way, the amount of applied toner of the print image is reduced in advance by the increase of the amount of applied toner of the specific color upon adding a copy-forgery-inhibited pattern image later. This can prevent a change in color tint upon copy-forgery-inhibited-pattern composition. 
     In S 37 , the applied amount control unit  407  further reduces the amount of applied toner of the print image in an image area where the amount of applied toner exceeds the maximum amount when the copy-forgery-inhibited pattern image is composited in the print image in which gamma correction processing has been done for the specific color in S 35 . The amount by which the amount of applied toner of the print image is reduced is a value obtained by subtracting the maximum amount of applied toner from the sum of the amount of applied toner of the print image having undergone gamma correction processing in S 35 , and that of applied toner of the copy-forgery-inhibited pattern image. In S 35 , gamma correction processing is executed for only the specific color of the print image. In an image region where the specific color is not contained in the first place, the amount of applied toner is not reduced and may exceed the maximum amount upon adding the copy-forgery-inhibited pattern image. To prevent this, the amount of applied toner of the print image needs to be further controlled. The amount of applied toner is reduced by the same method as that described in S 15  of the first embodiment. 
     As described above, in the third embodiment, the print image undergoes gamma correction processing for only a specific color which forms a copy-forgery-inhibited pattern image. As a result, the amount of applied toner is reduced uniformly in the entire image region (density region). Then, the same processing as that in the first embodiment is performed. As an effect of the third embodiment, a fixing error generated when the amount of applied toner exceeds the maximum amount can be prevented in copy-forgery-inhibited-pattern printing. In addition, gamma correction processing is executed for the print image to uniformly decrease the signal value of the specific color in advance in the entire image region (density region). This can suppress an increase in the amount of applied toner caused by compositing a copy-forgery-inhibited pattern image, and prevent a change in color tint upon adding the copy-forgery-inhibited pattern. 
     OTHER EMBODIMENTS 
     Aspects of the present invention can also be realized by a computer of a system or apparatus (or devices such as a CPU or MPU) that reads out and executes a program recorded on a memory device to perform the functions of the above-described embodiment(s), and by a method, the steps of which are performed by a computer of a system or apparatus by, for example, reading out and executing a program recorded on a memory device to perform the functions of the above-described embodiment(s). For this purpose, the program is provided to the computer for example via a network or from a recording medium of various types serving as the memory device (for example, computer-readable medium). 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application is a continuation of U.S. application Ser. No. 12/892,368, filed Sep. 28, 2010, which claims the benefit of Japanese Patent Application No. 2009-240878, filed Oct. 19, 2009, No. 2010-023550, filed Feb. 4, 2010, and No. 2010-207157, filed Sep. 15, 2010, which are hereby incorporated by reference herein in their entireties.