Patent attributes
A representative color determining step is executed to determine, from image data, a representative color characterizing an image of a print, and positions of the representative color. A gray control color determining step is executed to determine, from the image data, a gray control color expressed in an achromatic color and positions of the gray control color. A reading step is executed to read an image of reference paper and an image of an actual print. Then, a calculating step is executed to carry out a comparative calculation of color data in the positions of the representative color of the image of the reference paper and color data in the positions of the representative color of the image of the print, and a comparative calculation of color data in the positions of the gray control color of the image of the reference paper and color data in the positions of the gray control color of the image of the print, to create control data for controlling ink feeding rates of a printing machine.