Method and apparatus for calcuating color differences on measured evaluation charts to evaluate color reproducibility considering image homogeneity

A color processing apparatus for evaluating an image forming apparatus, the color processing apparatus comprising:

• a first input section, arranged to input data associated with spectral reflectances of a plurality of points on a first evaluation chart output from the image forming apparatus by supplying first image data that represents an image having a uniform density in a region to be evaluated in one page to the image forming apparatus to form the first evaluation chart;
• a first calculator, arranged to calculate color differences between a color at a predetermined point and colors at other points on the first evaluation chart based on the data associated with the spectral reflectances on the first evaluation chart;
• a second input section, arranged to input data associated with spectral reflectances of a plurality of points on a second evaluation chart output from the image forming apparatus by supplying second image data that corresponds to a color target for color matching to the image forming apparatus to form the second evaluation chart;
• a second calculator, arranged to calculate color differences between data associated with the spectral reflectances of the plurality of points on the second evaluation chart and data associated with spectral reflectances of the color target, which correspond to the plurality of points on the second evaluation chart;
• and
• a controller, arranged to control operation of said second input section and said second calculator so that when the color differences calculated by said first calculator fall within a permissible range of heterogeneity of colors in the region to be evaluated, said second input section and said second calculator operate, and when the color differences calculated in by said first calculator fall outside the permissible range, operations of said second input section and said second calculator are skipped.

A computer readable product storing a computer readable program enabling a computer to perform a method of evaluating an image forming apparatus, the method comprising the steps of:

• inputting data associated with spectral reflectances of a plurality of points on a first evaluation chart output from the image forming apparatus by supplying first image data that represents an image having a uniform density in a region to be evaluated in one page to the image forming apparatus to form the first evaluation chart;
• calculating color differences between a color at a predetermined point and colors at other points on the first evaluation chart based on the data associated with the spectral reflectances on the first evaluation chart;
• inputting data associated with spectral reflectances of a plurality of points on a second evaluation chart output from the image forming apparatus by supplying second image data that corresponds to a color target for color matching to the image forming apparatus to form the second evaluation chart;
• calculating color differences between data associated with the spectral reflectances of the plurality of points on the second evaluation chart and data associated with spectral reflectances of the color target, which correspond to the plurality of points on the second evaluation chart;
• and
• controlling execution of the second inputting step and the second calculating step so that when the color differences calculated in the first calculating step fall within a permissible range of heterogeneity of colors in the region to be evaluated, the second inputting step and the second calculating step are executed, and when the color differences calculated in the first calculating step fall outside the permissible range, execution of the second inputting step and the second calculating step is skipped.