Abstract:
An image processor includes an operation panel at which color adjustments for image data are set. A generation device generates a pattern signal which represents a state related to the set color and image data representing a test image. A processor processes the image data representing the test image on the basis of the set color adjustment. The processed image data and the pattern signal are then output by an output device such as a color printer.

Description:
This application is a continuation of application Ser. No. 08/097,206 filed Jul. 27, 1993, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image processing apparatus and an image forming apparatus, capable of varying the print density. 
     2. Related Background Art 
     Color printing apparatus generally reproduce colors of a predetermined number, by mixing inks or toners of yellow (Ye), magenta (Mg), cyan (Cy) and black (Bk) colors in suitable proportions. 
     The conventional color printing apparatus are capable of regulating the proportions of these coloring materials, but lack the function of releasing the result of such regulation as a sample. The result of regulation can only be confirmed, therefore, by the actual printing of a suitable color image (or color characters). 
     Also the result of regulation of the print density of Y, M, C and Bk colors has not been reflected on the printed result of the color sample or the test print. 
     Conventionally there has not been a measure for evaluating the color change corresponding to a color regulation, because of the lack of technology therefor, so that the actual printing has had to be executed. Such situation is encountered not only in the color printing but also in the monochromatic printing. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an image processing apparatus enabling easy density adjustment. 
     Another object of the present invention is to provide an image processing apparatus and an image forming apparatus enabling easier observation of the status of adjustment. 
     Still another object of the present invention is to provide an image processing apparatus and an image forming apparatus enabling easier observation of the status of color adjustment. 
     The above-mentioned objects can be attained, according to a preferred embodiment of the present invention, by an apparatus comprising setting means for setting a density with which an image is to be formed, generation means for generating test pattern signals including a pattern signal and a gray scale signal representing a state of the density set by the setting means, and process means for processing the test pattern signals, generated by said generation means, according to the setting by the setting means. 
     Still another object of the present invention is to provide an image processing apparatus and an image forming apparatus capable of satisfactory color reproductions respectively for characters and for other images. 
     Still another object of the present invention is to provide an image processing apparatus and an image forming apparatus with novel functions. 
     Still other objects of the present invention, and the features thereof, will become fully apparent from the following description of embodiments, to be taken in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram of a printing apparatus constituting an embodiment of the present invention; 
     FIG. 2 is a chart showing various gamma conversion tables used for color adjustment; 
     FIG. 3 is a flow chart for setting color adjustment phases from a panel; 
     FIG. 4 is a flow chart for printing a test print; 
     FIG. 5 is a flow chart for writing a raster image; 
     FIG. 6 is a flow chart for writing a color sample; 
     FIG. 7 is a flow chart for a color reproduction process; 
     FIG. 8 is a view showing an example of the test pattern; 
     FIG. 9 is a view showing an example of the color sample; 
     FIG. 10 is a block diagram of an embodiment of the present invention; 
     FIG. 11 is a chart showing gamma conversion characteristics; 
     FIG. 12 is a flow chart for setting color adjustment parameters; 
     FIG. 13 is a flow chart for a test print; 
     FIG. 14 is a flow chart showing details of a step S 119  in FIG. 13; 
     FIG. 15 is a flow chart showing details of a step S 132  in FIG. 14; 
     FIG. 16 is a view showing the result of a test print of the present embodiment; and 
     FIG. 17 is a view showing an example of the operation panel  124  shown in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a block diagram of a printing apparatus constituting an embodiment of the present invention. The printing apparatus  2 , provided with a microprocessor system including a ROM and a RAM, is connected to a host computer  1 , which sends print data and print commands to the printing apparatus  2 . 
     The printing apparatus  2  is also provided with an interface  21  for data exchange with the host computer  1 ; a control unit  22  for controlling the apparatus; an operation panel  23  for setting or varying printing parameters; a color reproducing information storage unit  24  for storing information necessary for color reproduction (gamma conversion table etc.); a color reproducing process unit  25 ; a command analysis unit  26  provided with a command search table  26 - 1  storing jump addresses to analysis programs corresponding to the command numbers of the print command transmitted from the host computer  1 , and serving to analyze the print data and the print commands sent from the host computer  1  thereby generating information of a page developable in a development memory; a page information unit (RAM)  27  for storing thus analyzed information of a page; a page information analysis unit  28  for analyzing thus stored page information; a development unit  29  for data development in a development memory  29 - 1 ; an output unit  2 A for forming a permanent visible image of the developed data on a recording sheet; a character pattern information unit  2 B storing the information for developing character patterns; a data bus  2 C; and a test pattern storage unit  100  for storing test pattern information as writing commands. 
     In the present embodiment, the page information storage unit  27  stores the color image information in the form of R, G and B data, while the development memory  29 - 1  stores Y, M, C and Bk data converted from the R, G and B data. It is also possible, however, to store the R, G and B data in the development memory  29 - 1  and to convert the data into the Y, M, C and Bk data immediately before the supply to the printer unit. 
     FIG. 2 shows various gamma conversion tables in the color process unit. The table converts the input densities of Y, M, C and Bk, calculated in 256 levels from a non-printed state “0” to a solid printed state “255”, into density information of Y, M, C and Bk of values from “0” to “255”. For example in gamma characteristics “−5” shown in FIG. 2, in response to input Y, M, C, Bk signals corresponding to solid printed density, there are obtained output signals of a value “102”, instead of the value “255” corresponding to the solid printed state. In this case, therefore, the colors are printed with a lower density in comparison with the input density. The color density adjustment is thus conducted by selecting a suitable gamma conversion table for the input density, thereby varying the output density. 
     FIG. 3 is a flow chart for setting, in a printing apparatus with color adjusting function, the color adjustment values of four colors Y, M, C and Bk from the operation panel  23 . A step S 1  selects the color adjustment mode from the panel  23 ; a step S 2  selects the color adjustment level of Y and sets it in NY; then a step S 3  selects the color adjustment level of M and sets it in NM; a step S 4  selects the color adjustment level of C and sets it in NC; a step S 5  selects the color adjustment level of Bk and sets it in NBk; and a step S 6  selects the gamma conversion table  24 - 1  in the color reproducing information storage unit  24 , utilizing the values of Y, M, C and Bk in the NY, NM, NC and NBk. 
     FIG. 4 is a flow chart for executing a test print, when an instruction for test printing is provided by the host computer  1 . A step S 1  selects the test print mode; a step S 2  reads a test print command from the test pattern storage unit  100 ; a step S 3  analyzes said command in the command analysis unit; a step S 4  sets the color adjustment level values NY, NM, NC and NBk in the color adjustment information set by the panel  23 ; then a step S 5  effects test printing of color adjustment information or effects dot development of said information in the page information storage unit  27 , in the same manner as a pattern A shown in FIG. 8; a step S 6  effects dot development of other print information such as data B shown in FIG. 8, then effects color processing by the color reproduction process unit  25 , according to the color adjustment state set by the panel  23  and effects printing in the output unit  2 A or dot development in the information storage unit  27  as explained before; and a step S 7  effects raster image writing. 
     FIG. 5 is a flow chart of raster image writing. A step S 1  reads the pixel data of R, G and B stored in the page information storage unit  28 ; a step S 2  effects a color reproduction process, involving conversion from the R, G, B data into the Y, M, C, Bk data; a step S 3  effects development of the pixel data of C, M, Y and Bk in the memory; a step S 4  discriminates whether all the pixel data have been read, and, if read, this routine is terminated, but, if not, the sequence returns to the step S 1 . 
     FIG. 7 is a flow chart of the color reproduction process in the step S 2  shown in FIG. 5. A step S 1  effects logarithmic conversion from the R, G, B luminance signals into Y, M, C density signals; a step S 2  effects undercolor removal and black color generation; a step S 3  effects color masking; and a step S 4  effects gamma conversion, with the density selected in the above-mentioned color adjustment mode. The data thus subjected to image processing are written into the development memory  29 - 1 . 
     FIG. 8 illustrates an example of the test print prepared in this embodiment. 
     The print shown in FIG. 8 includes: 
     a pattern A indicating the color adjustment levels in numerical presentation for the four colors Y, M, C and K. The presentation may be made in a graphical form, or in any other form that allows visual confirmation of the color adjustment state; 
     an area B for printing information indicating the available memory capacity in the development memory  29 - 1 , the page information storage unit, the page information analysis unit etc., the slot for inserting a font card and the available options; 
     an area C for printing information relating to the font; 
     an area D for printing information relating to the interface; 
     an area E for printing information relating to the memory size; 
     an area F for printing information relating to the layout; 
     an area G for printing information relating to the expanded functions; 
     an area H for printing information relating to the copy/overlay; and 
     a color pattern I of plural colors, including gray scales of Y, M, C and K, of which density is regulated by the color reproducing process unit  25  shown in FIG. 1, according to the numerical values in A, whereby the selected color adjustment levels can be visually confirmed in the form of actual densities, in addition to the numerical representation. 
     In the following embodiment, there will be described an example of printing a color sample from the host computer, instead of printing data representing the test pattern. 
     The hardware configuration of the apparatus will not be explained as it is the same as explained before. 
     FIG. 6 is a flow chart of the color sample printing. The color sample means a print of color palette data, provided in the apparatus, in a format as shown in FIG. 9, in which the square blocks indicate colors of mutually different hues. The color palette data show color numbers and color data of which combination of color components such as R, G and B is selected in advance, in correspondence with each of the color numbers. The correspondences between the color numbers and the combinations of the color component data can be varied by the host computer, and the color sample is printed in order to facilitate the understanding of such variable correspondences. Referring to FIG. 6, a step S 1  selects the color sample mode; a step S 2  reads a color sample command from the ROM: a step S 3  analyzes the command in the command analysis unit; a step S 4  sets the color adjustment levels NY, NM, NC and NBk as the color adjustment information; and a step S 5  writes the raster image. FIG. 5 shows the flow of raster image writing, in which a step S 1  reads the R, G and B data of a pixel; a step S 2  effects the color reproducing process; a step S 3  develops the pixels data of C, M, Y and Bk in the memory; and a step S 4  discriminates whether all the pixel data have been read, and, if read, the raster image writing routine is terminated, but, if not, the sequence returns to the step S 1 . 
     In the embodiment shown in FIG. 9, the color adjustment levels A′ may also be printed in a similar manner as the data A in FIG.  8 . 
     In the present embodiment there has been explained an example of printing the color test pattern, but the present invention also includes the case of test pattern printing or sample printing of a monochromatic gray scale. 
     As described in the foregoing, in a printing apparatus capable of color printing and varying the print density, the present embodiment effects the color sample printing or the test printing with adjusted colors when the color density is adjusted, whereby the user can directly observe the changes in colors and understand the result of the color adjustment. 
     Also in such color sample printing or test printing, numerical data indicating the state of color adjustment are printed at the same time, and such numerical data are useful in varying the color adjustment state again. 
     FIG. 10 shows another embodiment of the present invention, wherein a host computer  110  provides a color printer  112  of the present embodiment with print data. 
     The color printer  112  is provided therein with an interface  120  for receiving data (print data and control data) from the host computer  110 ; a control circuit (microcomputer)  122  for controlling the entire printer; and an operation panel  124  for entering the operation mode and various parameters into the control circuit  122 . 
     A color reproducing information storage circuit  126  stores information required for color reproduction, in the form of gamma conversion tables NY 1 , NM 1 , NC 1 , NBk 1 ; NY 2 , NM 2 , NC 2 , NBk 2 ; NY 3 , NM 3 , NC 3 , NBk 3  respectively for characters, images and character/images as will be explained later. A circuit  128  is provided for a color reproducing process. 
     A command analysis circuit  130 , for analyzing the print data and control data from the host computer  110  and generating print information of a page (page information), is provided with a command table  130   a  storing jump addresses for the analysis programs corresponding to the print command numbers from the host computer  110 . 
     A page information storage circuit  132 , consisting of a RAM, serves to temporarily store the page information, obtained by the analysis in the command analysis circuit  130 . 
     In the following there will be described an embodiment, in a color printing apparatus equipped with means for adjusting the output color density, enabling arbitrary density adjustment by the adjusting means at the test printing. 
     There are also provided a page information analysis circuit  134  for analyzing the page information stored in the page information storage circuit  132 ; a development circuit  136  for developing the information to be printed as an image on a development memory  136   a , according to the result of analysis by the analysis circuit  134 ; an output circuit  138  for printing the bit map data, developed in the development memory  136   a , on a recording sheet; and a character pattern information storage circuit  140  storing character pattern information of various characters. 
     FIG. 17 is a view of the operation panel  124  shown in FIG. 10, wherein keys  124 - 1 ,  124 - 2  are provided for selecting the color adjustment modes for characters or for images; designations keys  124 - 6 ,  124 - 8 ,  124 - 10 ,  124 - 12  for designating the color components Y, M, C and Bk in the color adjustment modes; display units  124 - 14 ,  124 - 16 ,  124 - 18 ,  124 - 20  for displaying the density adjusted states of the Y, M, C and Bk colors; and keys  124 - 22 ,  124 - 24  for elevating and lowering the adjusted density levels of the Y, M, C and Bk colors. 
     The circuits  120 - 140  are mutually connected by a system bus  142 . 
     The gamma conversion table  126   a  of the color reproducing information storage circuit  126  stores the information on the gamma conversion characteristics as shown in FIG.  11 . The characteristics are similar to those shown in FIG. 2, but are provided in a larger number in order to appropriately print the characters and images. The values of Y, M, C and Bk, obtained by processing the print data from the host computer  110 , in 256 levels from a non-printed state “0” to a solid printed state “255”, are converted within a range from 0 to 255. For example, for a parameter of −5 in FIG. 11, an input signal corresponding to the solid printed state is converted into an intermediate output signal at a level  102 . Although FIG. 11 shows linear conversions, there may naturally be employed nonlinear conversions, and, for this reason the conversions shown in FIG. 11 are called gamma conversions. 
     FIG. 12 shows a flow chart for setting the color adjustment values for Ye, Mg, Cy and Bk colors from the operation panel  124 . The operator selects the color adjustment mode for characters or for images by actuating the key  124 - 1  or  124 - 2  on the operation panel  124  (step S 101 ), and enters the color adjustment parameters for the Ye, Mg, Cy and Bk colors in succession, whereupon the control circuit  122  sets the entered parameters as variables NY 1 , NM 1 , NC 1  and NBk 1  for designating the gamma conversion tables (steps S 102 , S 103 , S 104  and S 105 ). The default value of said variables is “0”. In the embodiment shown in FIG. 11, each of the entered parameters NY 1 , NM 1 , NC 1 , NBk 1  assumes an integral value within a range from −7 to +7. 
     The control circuit  122  sets, for each color, a gamma conversion table among those  126   a , according to the parameters NY 1 , NM 1 , NC 1 , NBk 1  entered from the operation panel  124  (step S 106 ). Also the operator in advance designates the character patterns or images as the object of color adjustment at the test printing, to the control circuit  122  through the operation panel  124 . Thus, a selection can be made as to whether to apply a same color adjustment or different color adjustments to the character and images. 
     FIG. 13 is a flow chart of the test printing sequence. In this example, the color adjustment can be applied to the characters only, the test image only or both. 
     According to the selection of the test print mode by the operator through the operation panel  124  (step S 111 ), the control circuit  122  reads the test print command from the unrepresented ROM (step S 112 ), and supplies the command to the command analysis circuit  130 , which analyzes said test print command (step S 113 ). 
     If the color adjustment is designated for the characters only in the test print image represented by the test print command (step S 114 ), the character printing color information is subjected to gamma conversion utilizing the color adjustment parameters NY 1 , NM 1 , NC 1 , NBk 1  set in the sequence shown in FIG. 11, but the color adjustment is not applied to other images (step S 115 ). 
     Also if the color adjustment is designated for the images only (step S 114 ), the image printing color information is subjected to the gamma conversion utilizing the color adjustment parameters NY 2 , NM 2 , NC 2 , NBk 2  set in the sequence shown in FIG. 11 but the color adjustment is not applied to the characters (step S 116 ). 
     In case the color adjustment is applied to both of the characters and the images, or in case no separate color adjustments are designated for the characters and the images (step S 114 ), the printing color information for both is subjected to the gamma conversion, utilizing the parameters NY 3 , NM 3 , NC 3 , NBk 3  set in the sequence shown in FIG.  11 . 
     After the steps S 115 , S 116  and S 117 , the printing condition information, including the set color adjustment parameters NY, NM, NC, NBk, is developed into a bit map in the development memory  136   a , and the image of test print is converted into raster data and stored in a predetermined portion (for example an area different from the area for the printing condition information) in the development memory  136   a  (step S 119 ). Then the data stored in the development memory  136   a  are supplied to the output circuit  138  and printed on the recording sheet (step S 120 ). 
     FIG. 14 is a flow chart showing the details of the step S 119  in FIG. 13. A step S 131  reads the R, G and B data of a pixel, then a step S 132  effects the color reproducing process by the color reproducing process circuit  128  and conversion into the C, M, Y and Bk data, and a step S 133  stores the data in predetermined areas of the development memory. After the steps S 131 , S 132  and S 133  are executed for all the pixels, the sequence returns to the flow shown in FIG.  13 . 
     If separate color adjustments are designated for the characters and the images in this embodiment, the step S 132  identifies the corresponding command and utilizes the color adjustment parameters NY 1 , NM 1 , NC 1 , NBk 1  for the development of characters and parameters NY 2 , NM 2 , NC 2 , NBk 2  for the development of images. This point defines the difference from the flow chart shown in FIG.  5 . 
     FIG. 15 is a flow chart showing details of the color reproducing process in the step S 132  shown in FIG.  14 . The R, G, B luminance data are logarithmically converted into C, M, Y density data (S 141 ), and a black signal is generated with the removal of undercolor (S 142 ). Then masking is conducted (S 143 ), and gamma conversion is executed by the table  26   a  (S 144 ). 
     FIG. 16 shows an example of a test print obtained in the apparatus of the present embodiment. Different from the example shown in FIG. 8, there are printed parameters A for the characters only, and B for the image only, together with the test print image. Consequently the user can recognize the state of test print in numerical presentation. 
     The image for such test print may naturally be replaced by a suitable test pattern. 
     As explained in the foregoing, the present embodiment allows to confirm the results of color adjustments for the characters and for the image, in the actual printed colors.