Color image processing method and apparatus

A color image processing method for performing color separation to separate image data colors into primary four color-material colors and pale color-material colors of predetermined ones of the primary color-material colors, comprising:

• a setting step of setting a target gray line connecting white to black for the color separation in predetermined color space;
• a three color gray generation step of obtaining a combination of three color materials to realize a color on the target gray line;
• a four color separation processing step of determining amounts of the primary four color materials to realize the color on the target gray line;
• a total color material amount determination step of determining a total color material amount to realize the target gray line;
• and
• a color-material amount determination step of, regarding a color which cannot be realized by the combination of primary Y color and the pale color-material colors to realize the color on the target gray line, determining respective color material amounts of the color materials based on the total color material amount and the color material amounts of the primary four colors.

A color image processing apparatus for performing color separation to separate image data colors into primary four colors represented by four color-materials, at least one of which is constituted by pale color-material and deep color-material, comprising:

• obtaining means for obtaining a density or luminance characteristics when the pale color-material and deep color-material are mixed;
• first setting means for setting a target density or target luminance after the pale color-material and deep color-material are separated;
• second setting means for setting a total amount of color-materials after the pale color-material and deep color-material are separated;
• and
• acquisition means for acquiring an amount of the pale and deep color-materials to obtain the target density or target luminance and the total amount of color-materials, based on the density or luminance characteristics obtained by said obtaining means.