Abstract:
A color processing method has a first conversion process for converting on a fixed basis colorimetry data representative of colorimetry values into CMY color data representative of a combination of values of C, M and Y, and a second conversion process for converting the CMY color data obtained in said first conversion process into color data depending on a device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a color processing method of applying color processing to measured data representative of colorimetry values, for example, XYZ values and L*a*b* values so that a high quality of image can be obtained by, for example a printing system and a printer, a color processing apparatus and a color processing program storage medium storing a color processing program, when executed in a computer, which causes the computer to operate as the color processing apparatus. 
     2. Description of the Related Art 
     Hitherto, as an apparatus for applying a high quality of color processing for printing to image data representative of an image, there is known an apparatus in which CMY data representative of a combination of density values of C, M, Y and K is inputted and CMYK data representative of a combination of dot % values of C, M and Y is outputted (cf. for example, Japanese Patent Laid Open Gazette Hei.9-83824, U.S. Pat. No. 6,002,806). 
     This apparatus is for performing color processing in accordance with an input of CMY data, and is recently improved in various respects. However, such an apparatus is basically established in technology in some extent. There are many experts who are able to perform a high quality of color processing (this type of color processing is referred to as a “set up”) through operating the apparatus as mentioned above. 
     However, recently, as a color management technology becomes popular, there is enhanced a necessity that color data other than CMY data as well is subjected to color processing with high quality. For example, a color management by an ICC profile is spread. In this case, input data to a color processing apparatus is measured data representative of colorimetry values such as XYZ values and L*a*b* values. To use the measured data for printing, there is needed an apparatus for performing a color conversion of the measured data into CMYK data. However, a color processing technology capable of processing such a color conversion of data in high quality is not yet established. Further, to perform a high quality of color processing, technique of an expert is indispensable. However, the expert has no technique of performing a high quality of set up in accordance with colorimetry data, while the expert is skilled in set up based on CMY data through input of the CMY data. 
     As described above, while necessity for performing a high quality of color processing in accordance with colorimetry data is increased, a processing system for implementing this is not yet established. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the present invention to provide a color processing method capable of performing a high quality of color processing in accordance with colorimetry data, a color processing apparatus and a color processing program storage medium storing a color processing program, when executed in a computer, which causes the computer to operate as the color processing apparatus capable of performing a high quality of color processing in accordance with colorimetry data. 
     To achieve the above-mentioned object, the present invention provides a color processing method comprising: 
     a first conversion process for converting on a fixed basis colorimetry data representative of colorimetry values into CMY color data representative of a combination of values of C, M and Y; and 
     a second conversion process for converting the CMY color data obtained in said first conversion process into color data depending on a device. 
     Here, the above-mentioned “converting on a fixed basis” implies a conversion to be performed on a fixed basis regardless of sorts of images, but not a conversion to be performed adaptively for each image. 
     In the color processing method according to the present invention as mentioned above, it is preferable that said first conversion process comprises: an RGB data creating process for converting the colorimetry data into RGB data representative of a combination of values of three primary colors R, G and B, and; a CMY data creating process for subjecting the values of three primary colors R, G and B represented by the RGB data obtained in said RGB data creating process to a logarithmic transformation to create CMY data representative of a combination of values of C, M and Y. In this case, it is preferable that the color processing method further comprises a parameter computing process for computing parameters of converting the colorimetry data into the RGB data in accordance with a chromaticity value of a predetermined white point on an x-y chromaticity view and chromaticity values of three points associated with three primary colors R, G and B on the x-y chromaticity view, and said RGB data creating process converts the colorimetry data into the RGB data in accordance with the parameters computed in said parameter computing process. In this case, it is preferable that said parameter computing process provides such a definition that vertexes of a triangle are defined as three points associated with three primary colors R, G and B, said vertexes being located at three straight lines on the x-y chromaticity view, coupling three points, which represent main wave lengths of three primary colors R, G and B in a color reproduction area on the x-y chromaticity view, corresponding to an assembly of entire colors reproducible in a colorimetry system for obtaining the colorimetry data, with a predetermined white point on the x-y chromaticity view, respectively, where said triangle includes the color reproduction area. 
     Here, in the above-mentioned “colorimetry system”, an image before the color processing is recorded. The colorimetry system implies a concept including all having an effect on generation of colorimetry data as an object of color processing, for example, characteristics of image recording medium such as a reversal film, and characteristics of image input apparatuses for reading images and colors from the image recording medium to obtain image data and color data as colorimetry values. In this case, in the event that colorimetry data of sufficiently wide reproduction area can be obtained in view of characteristics of an image input apparatus per se, characteristics of an image recording medium (for example, the color reversal film) on which an image to be converted into colorimetry data by the image input apparatus define a color reproduction area on the x-y chromaticity view. 
     In the color processing method according to the present invention as mentioned above, as an typical example, said second conversion process converts the CMY color data obtained in said first conversion process into CMYK data representative of a combination of values of C, M, Y and K. 
     To achieve the above-mentioned object, the present invention provides a color processing apparatus comprising: 
     a first conversion section for converting on a fixed basis colorimetry data representative of colorimetry values into CMY data representative of a combination of values of C, M and Y; and 
     a second conversion section for converting the CMY color data obtained in said first conversion section into color data depending on a device. 
     Further, to achieve the above-mentioned object, the present invention provides a color processing program storage medium storing a color processing program which causes a computer to operate as a color processing apparatus, when the color processing program is executed in the computer system, wherein said color processing program storage medium stores the color processing program comprising: 
     a first conversion section for converting on a fixed basis colorimetry data representative of colorimetry values into CMY data representative of a combination of values of C, M and Y; and 
     a second conversion section for converting the CMY color data obtained in said first conversion section into color data depending on a device. 
     The color processing apparatus of the present invention includes any types of apparatuses for implementing any types of image processing methods of the present invention. A color processing program, which stores the color processing program storage medium of the present invention, includes any types of programs which causes a computer to operate as an apparatus for implementing any types of image processing methods of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic constitution view of an image input-color conversion-image output system to which an embodiment of the present invention is applied. 
         FIG. 2  is a perspective view of a personal computer. 
         FIG. 3  is a hardware structural view of the personal computer. 
         FIG. 4  is a view showing an embodiment of a color processing program storage medium according to the present invention. 
         FIG. 5  is a functional block diagram of an embodiment of a color processing apparatus according to the present invention. 
         FIG. 6  is a flowchart useful for understanding an embodiment of a color processing method of the present invention. 
         FIG. 7  is a view showing x-y chromaticity view. 
         FIG. 8  is a view showing x-y chromaticity view. 
         FIG. 9  is a view showing x-y chromaticity view. 
         FIG. 10  is a block diagram of a color processing section which is an example of the second conversion section of the color processing apparatus shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a schematic constitution view of an image input-color conversion-image output system to which an embodiment of the present invention is applied. 
     An image-input device  10  reads an original image  11  recorded on a reversal film and produces colorimetric image data represented by colorimetry values of XYZ. The colorimetric image data of XYZ produced by the image-input device  10  is fed to a personal computer  20 . The personal computer  20  converts the colorimetric image data obtained by the image-input device  10  into image data for printing representative of dot % for CMYK suitable for a printing system  30 , which will be described later. The image data for printing is fed to the printing system  30 . The printing system  30  performs a printing so that a print image  31  is formed. 
     An aspect as an embodiment of the present invention in the system shown in  FIG. 1  resides in processing contents to be executed inside the personal computer  20 . Hereinafter, there will be described the personal computer  20 . 
       FIG. 2  is a perspective view of the personal computer  20  shown in  FIG. 1 .  FIG. 3  is a hardware structural view of the personal computer  20 . 
     The personal computer  20  comprises, on an external appearance, a main frame unit  21 , an image display unit  22  for displaying an image on a display screen  22   a  in accordance with an instruction from the main frame unit  21 , a keyboard  23  for inputting various sorts of information to the main frame unit  21  in accordance with a key operation, and a mouse  24  for inputting an instruction according to, for example, an icon and the like, through designation of an optional position on the display screen  22   a , the icon and the like being displayed on the position on the display screen  22   a . The main frame unit  21  has a floppy disk mounting slot  21   a  for mounting a floppy disk, and a CD-ROM mounting slot  21   b  for mounting a CD-ROM. 
     The main frame unit  21  comprises, as shown in  FIG. 3 , a CPU  211  for executing a various types of program, a main memory  212  in which a program stored in a hard disk unit  213  is read out and developed for execution by the CPU  211 , the hard disk unit  213  for saving various types of programs and data, an FD drive  214  for accessing a floppy disk  100  mounted thereon, a CD-ROM drive  215  for accessing a CD-ROM  110  mounted thereon, an input interface  216  connected to the image-input device  10  (cf.  FIG. 1 ), to receive image data from the image-input device  10 , and an output interface  217  to transmit image data to the printing system  30 . These various types of elements are connected via a bus  25  to the image display unit  22 , the keyboard  23  and the mouse  24 . 
     The CD-ROM  110  stores therein a color processing program for causing the personal computer  20  to operate as a color processing apparatus. The CD-ROM  110  is mounted on the CD-ROM drive  215  so that the color processing program, which is stored in the CD-ROM  110 , is up-loaded on the personal computer  20  and is stored in the hard disk unit  213 . 
       FIG. 4  is a view showing an embodiment of a color processing program storage medium according to the present invention. The color processing program storage medium shown in  FIG. 4  represents storage medium such as the CD-ROM  110  shown in  FIG. 3  and the hard disk in the hard disk unit  213 . 
     A color processing program storage medium  300  stores a color processing program  310  comprising a first conversion section  320 , a second conversion section  330  and a parameter computing section  340 . The first conversion section  320  comprises an RGB data creating section  321  and a CMY data creating section  322 . Operations of the respective sections of the color processing program  310  will be described later. 
     When the color processing program  310  is stored in the CD-ROM  110  shown in  FIG. 3 , the CD-ROM  110  corresponds to an example of a color processing program storage medium of the present invention, and when the color program  310  stored in the CD-ROM  110  is loaded onto the personal computer  20  and stored in the hard disk unit  213 , the hard disk storing the color processing program  310  corresponds to an example of a color program storage medium of the present invention. Further, when the color processing program  310  within the hard disk is down loaded onto the floppy disk  100  shown in  FIG. 3 , the floppy disk storing the color processing program  310  also corresponds to an example of a color processing program storage medium of the present invention. 
       FIG. 5  is a functional block diagram of an embodiment of a color processing apparatus according to the present invention. 
     A color processing apparatus  410  shown in  FIG. 5  is implemented when the color processing program  310  shown in  FIG. 4  is loaded onto the personal computer  20  and is executed by the personal computer  20 . 
     The color processing apparatus  410  shown in  FIG. 5  comprises a first conversion section  420 , a second conversion section  430  and a parameter computing section  440 . The first conversion section  420  comprises an RGB data creating section  421  and a CMY data creating section  422 . 
     The first conversion section  420 , which comprises the RGB data creating section  421  and the CMY data creating section  422 , the second conversion section  430 , and the parameter computing section  440  in the color processing apparatus  410  shown in  FIG. 5  comprise the combinations of the first conversion section  320 , which comprises the RGB data creating section  321  and the CMY data creating section  322 , the second conversion section  330 , and the parameter computing section  340 , which are shown in  FIG. 4  as software parts, with the hardware of the personal computer  20  and the operating systems (OS), respectively. 
       FIG. 6  is a flowchart useful for understanding an embodiment of a color processing method of the present invention. 
     In the explanation of the flowchart of  FIG. 6 , there will be explained the color processing program shown in  FIG. 4  and the color processing apparatus shown in  FIG. 5 . 
     In the flowchart of  FIG. 6 , there are shown a first conversion process (step (a)) which is executed when the color conversion processing is carried out, a second conversion process (step (b)), and a parameter computing process (step (c)) which is a preparatory process before the color conversion processing is carried out. The first conversion process (step (a)) comprises an RGB data creating process (step (a 1 )) and a CMY data creating process (step (a 2 )). 
     In the RGB data creating process (step (a 1 )) of the first conversion process (step (a)), XYZ values represented by the colorimetric image data produced by the image-input device  10  are converted into RGB values in accordance with formula (1) as set forth below. 
     Incidentally, as typical examples of a color system representative of colorimetry values, there are, for example, L*a*b* and the like other than XYZ. However, they can be converted into XYZ, and thus here it will be explained assuming that XYZ are dealt with. 
     
       
         
           
             
               
                 
                   
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     Here, elements A ij  (i, j=1, 2, 3) of the matrix (A ij ) is determined in the parameter computing process (step (c)), and thus, first, the parameter computing process (step (c)) will be explained hereinafter. 
     Each of  FIGS. 7 to 9  is a view showing x-y chromaticity view. 
     In  FIG. 7 , there is shown a color reproduction area  710  in an entire color area  700  surrounding the whole area of the existing colors. The color reproduction area  710  is an area in which a color chart consisting of a large number (for example, 729 colors) of color patches, which is the maximum capable of being represented as color on a reversal film having the same characteristic as a reversal film on which the original image  11  (cf.  FIG. 1 ) is recorded, is created, and a large number (for example, 729 colors) of points on the x-y chromaticity view, which are determined from colorimetry data for XYZ obtained through reading by the image-input device  10 , is encircled. 
     A relationship between the colorimetry data for XYZ and coordinate points (x, y) on the x-y chromaticity view is as follows.
 
 x=X /( X+Y+Z )
 
 y=Y /( X+Y+Z )  (2)
 
     A z chromaticity value is expressed by the following formula (3).
 
 z =1 −x−y=Z /( X+Y+Z )  (3)
 
     While the z chromaticity value is not necessary for a notation of the x-y chromaticity view of  FIGS. 7 to 10 , it is necessary for the latter computation. 
     Next, as shown in  FIG. 8 , a predetermined white point is determined on the x-y chromaticity view. According to the present embodiment, the following point (x w , y w ), which represents the chromaticity value of light D 50  of the auxiliary standard of CIE, is defined as a white point  720 .
 
( x   w   , y   w )=(0. 3 4 5 7, 0. 3 5 8 6)  (4)
 
     Next, let us consider on the x-y chromaticity view three straight lines  721 ,  722  and  723 , which couple the white point  720  with the coordinate points  711 ,  712  and  713  (vertexes of roughly triangle of the color reproduction area  710 ) corresponding to the primary color of the color reproduction area  710 , respectively, and in addition, as shown in  FIG. 9 , a triangle  730  having its vertexes on the three straight lines and including the color reproduction area  710 . It is desirable for the triangle  730  that it is set up in such a manner that the triangle  730  includes the color reproduction area  710  and the area is minimum. 
     According to the present embodiment, the vertexes of the triangle  730  thus set up are denoted in form of primary color points  731 ,  732  and  733 , which are representative of chromaticity values of primary colors of G, B and R, respectively. 
     From the white point  720  and the three primary color points  731 ,  732  and  733  thus determined, elements A ij  of the matrix (A ij ) of the transformation formula shown in the formula (1) are determined as follows (cf. “Foundations of Color Engineering” by Mituo Ikeda, pages 125 to 130, (Kabushiki Kaisha) Asakura Bookstore). 
     Here, x y z chromaticity values (x, y, z) of the white point  720  are represented by (x w , y w , z w ). x y z chromaticity values of the primary color points  731 ,  732  and  733  are represented by (x G , y G , z G ), (x B , y B , z B ), (x R , y R , z R ), respectively. 
     Formula (1) is expressed by
 
 R=A   11   X+A   12   Y+A   13   Z 
 
 G=A   21   X+A   22   Y+A   23   Z 
 
 B=A   31   X+A   32   Y+A   33   Z   (5)
 
(a) with respect to the white point (x w , y w , z w ),
 
 A   11   x   w   +A   12   y   w   +A   13   z   w =1
 
 A   21   x   w   +A   22   y   w   +A   23   z   w =1
 
 A   31   x   w   +A   32   y   w   +A   33   z   w =1  (6)
 
(b) with respect to primary color point (x G , y G , z G ) of G,
 
 A   11   x   G   +A   12   y   G   +A   13   z   G =0
 
 A   31   x   G   +A   32   y   G   +A   33   z   G =0  (7)
 
(c) with respect to primary color point (x B , y B , z B ) of B,
 
 A   11   x   B   +A   12   y   B   +A   13   z   B =0
 
 A   21   x   B   +A   22   y   B   +A   23   z   B =0  (8)
 
(d) with respect to primary color point (x R , y R , z R ) of R,
 
 A   21   x   R   +A   22   y   R   +A   23   z   R =0
 
 A   31   x   R   +A   32   y   R   +A   33   z   R =0  (9)
 
     Taking notice of formulas including for example, A 11 , A 12 , A 13  in the expression (6) to (9), the following three formulas exist.
 
 A   11   x   w   +A   12   y   w   +A   13   z   w =1
 
 A   11   x   G   +A   12   y   G   +A   13   z   G =0
 
 A   11   x   B   +A   12   y   B   +A   13   z   B =0
 
     Solving those three simultaneous equations makes it possible to determine A 11 , A 12 , A 13 . Likewise, there exist three formulas including A 21 , A 22 , A 23 , too, and there exist three formulas including A 31 , A 32 , A 33 , too. Solving those simultaneous equations makes it possible to determine all elements A ij  (i , j=1, 2, 3) of the matrix (A ij ) of the formula (1). In the present embodiment, those elements A ij  correspond to the parameter referred to in the present invention. 
     In the present embodiment as mentioned above, the white point and the primary color point are rather strictly determined. However, it is acceptable that those points are empirically determined in some extend, without passing through such a strict step, and the elements of the matrix of the formula (1) are determined in accordance with coordinates of those points. In this case, however, as compared with a case where those points are strictly determined as mentioned above in accordance with the present embodiment, there is a possibility that an accuracy of the final color processing is lowered, or an operator is obliged to have a load in order to avoid such a matter that an accuracy of the final color processing is lowered. 
     In the parameter computing process of the step (c) of  FIG. 6 , in the manner as mentioned above, parameters (in the example as mentioned above the elements A ij  of the matrix (A ij ) of the formula (1)) are computed. The parameters thus computed are saved for the purpose of color conversion processing for the actual image (the original image  11  shown in  FIG. 1 ). 
     In the color processing program  310  shown in  FIG. 4  and the color processing apparatus  410  shown in  FIG. 5 , the parameter computing section  340  and the parameter computing section  440  serve to perform processing of the parameter computing process of the step (c) of  FIG. 6 , respectively. 
     Next, there will be described color conversion processing for the actual image. When the image-input device  10  (cf.  FIG. 1 ) is used to read the original image  11  recorded on a color reversal film, colorimetry data (XYZ values) on the respective points of the original image are obtained. 
     The colorimetry data (XYZ values) are converted into RGB data in accordance with the formula (1) in the RGB data creating process (step (a 1 )) of the first conversion process (step (a)) shown in  FIG. 6 , and then in the CMY data creating process (step (a 2 )) of the first conversion process (step (a)), CMY data are determined from RGB data determined in the RGB data creating process (step (a 1 )) in accordance with the following formula (10).
 
 C =−1  o g R 
 
 M =−1  o g G 
 
 Y =−1  o g B   (10)
 
     In the color processing program  310  shown in  FIG. 4  and the color processing apparatus  410  shown in  FIG. 5 , the RGB data creating section  321  of the first conversion section  320  and the RGB data creating section  421  of the first conversion section  420  serve to perform processing of the RGB data creating process (step (a 1 )) of the first conversion process (step (a)) shown in  FIG. 6 , respectively. Further, in the color processing program  310  shown in  FIG. 4 , the CMY data creating section  322  of the first conversion section  320  serves to perform processing of the CMY data creating process (step (a 2 )) of the first conversion process (step (a)) shown in  FIG. 6 . And in the color processing apparatus  410  shown in  FIG. 5 , the CMY data creating section  422  of the first conversion section  420  serves to perform processing of the CMY data creating process (step (a 2 )) of the first conversion process (step (a)) shown in  FIG. 6 . 
     The second conversion process (step (b)) of the flowchart in  FIG. 6  is a process of obtaining CMYK data through applying the color conversion processing with great accuracy for each image utilizing skills of an operator. 
     In the first conversion process (step (a)), the colorimetry data are converted into CMY data in the manner as mentioned above. Consequently, in the second conversion process (step (b)), it is possible to perform the color processing based on the CMY data. Thus, it is possible to perform the color conversion processing with great accuracy using technique familiar to an operator. 
     In the second conversion section  330  constituting the color processing program shown in  FIG. 4  and the second conversion section  430  constituting the color processing apparatus shown in  FIG. 5 , there is constructed an algorithm useful for performing a color conversion from CMY data into CMYK data. An operator controls various sorts of parameters to define the algorithm, so that the color conversion from CMY data into CMYK data is performed in accordance with the parameters after controlled. 
     The fundamental algorithm of the second conversion section (the second conversion process) is well known. 
     However, here, applicants introduce an example of the recent algorithms (cf. Japanese Patent Application Serial No. Hei. 11-353006). 
       FIG. 10  is a block diagram of a color processing section which is an example of the second conversion section  430  of the color processing apparatus  410  shown in  FIG. 5 . Here, in order to mutually distinguish CMY data, CMY data, which is determined in the first conversion section  420  and is transmitted to the second conversion section  430 , is addressed as color data CMY 0 . 
     The color data CMY 0 , which are entered to a color processing section  520 , is first fed to a range set up section  521 . 
     The range set up section  521  designates a range width in accordance with a designation value of dye density in the highlight on the original image and a designation value of dye density in the shadow on the original image, applies a normalization according to the range width to the color data CMY 0 , and outputs the normalized color data CMY 1 . 
     The color data CMY 1 , that is outputted from the range set up section  521 , is fed to a gradation conversion section  522  and a K-plate creating section  525 . 
     The gradation conversion section  522  is set up with tone curves for C, M and Y three colors corrected by a correction coefficient of the highlight of the tone curve, a correction coefficient of the shadow, and a correction coefficient of the middle. The gradation conversion section  522  determines color data CMY 2  by a gradation conversion of the color data CMY 1  using those tone curves. 
     The color data CMY 2  determined by the gradation conversion section  522  is fed to a UCR section  523  for performing a UCR operation to determine gray component values CMY U , which are to be subtracted from the color data CMY 2 , in accordance with parameter values set up by an operator. The gray component values CMY U  thus determined is subtracted from the color data CMY 2  outputted from the gradation conversion section  522 , so that color data CMY 3  is created. 
     The color data CMY 3 , which are subtracted in the gray component, are fed to a gray balance section  524  in which a gray balance of the color data CMY 3  is corrected to a gray balance of dot % values based on the color characteristic of the printing ink. Correction of the gray balance of the color data CMY 3  makes it possible to convert the color data CMY 3  into dot % values of C, M and Y three colors of dot % values of C, M, Y and K four colors. 
     On the other hand, the K-plate creating section  525 , which receives the color data CMY 1  outputted from the range set up section  521 , determines the minimum value of the dye density value C 1 , M 1  and Y 1  represented by the color data CMY 1 , so that a gray component value K a  of a color represented by the color data CMY 1  is determined. And the gray component value K a , which is determined by the K-plate creating section  525 , is fed to a K-plate curve section  526  in which a K-plate curve, which represents the percentage of components to be replaced by a K-plate in the gray component as a function of the gray component value K a , is used to convert the gray component value K a  into a dot % value for the K-plate. 
     The color processing section  520  shown in  FIG. 10  is provided with further a color correction section  527  for performing a color correction operation. The color correction section  527  is set up with color correction coefficients for controlling color variations in color directions of R, Y, G, C, B and M for each of divisional plates of C, M, Y and K four colors. The color correction section  527  receives the color data CMY 2  determined by the gradation conversion section  522 , and determines color correction data ΔCMYK representative of correction quantity of dot % values for C, M, Y and K four colors, which correspond to color variations according to the color data CMY 2  and the color correction coefficient. Of the color correction data ΔCMYK, C, M and Y three colors component is added to the dot % values outputted from the gray balance section  524 , so that C, M and Y three colors of dot % values CMY 4  are created for reproduction of a color after the color conversion. On the other hand, of the color correction data ΔCMYK, the black component is added to the dot % values for the K-plate outputted from the K-plate curve section  526 , so that dot % value K 4  for the K-plate is created for reproduction of a color after the color conversion. 
     The C, M and Y three colors of dot % values CMY 4  and the dot % value K 4  for the K-plate thus created are fed to %—% conversion sections  528  and  529 , respectively, to be subjected to a fine correction for dot % values and be outputted in form of dot % values CMY P  and K p  for printing, respectively. 
     The dot % values CMY P  and K p  thus outputted are transmitted to the printing system  30  (cf.  FIG. 1 ) in form of printing image data. The printing system  30  creates divisional plates for printing in accordance with the transmitted printing image data and performs a printing, so that a preferable color is reproduced on a printed matter. 
     The color processing section  520  (the second conversion section  430  shown in  FIG. 5 ) shown in  FIG. 10  is set up with a large number of various parameters and performs color conversion processing according to the set up parameter. The set up of the parameters is deeply involved in technique of an operator. The color processing section  520  (the second conversion section  430 ) are to perform a conversion from the conventional CMY data to the CMYK data. Thus, an operator can perform a great accuracy of color conversion processing making good use of one&#39;s experience. 
     As mentioned above, according to the present invention, colorimetry data are once converted into CMY data, and color processing is performed on the converted CMY data. This feature makes it possible to make good use of one&#39;s property for performing a great accuracy of processing accumulated, that is, the former color processing apparatus, technique of color processing and technique of an operator. And thus, it is possible to perform a great accuracy of color processing. 
     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and sprit of the present invention.