Patent ID: 7800798

Claim:
A print quality measuring method for comparing an image of reference paper and a printed image of a print corresponding to the image of the reference paper for controlling ink feeding rates of a printing machine, the method comprising: a reading step for reading, by using an image pickup device, the image of the reference paper and the printed image of the print; a representative color determining step for determining, from image data to be printed, a representative color characterizing the printed image of the print, and positions of the representative color; and a calculating step for carrying out, by using a calculating device including a CPU, 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 printed image of the print, to create control data for controlling the ink feeding rates of the printing machine, wherein the representative color and the positions thereof are determined for respective rectangular sections on a printing paper corresponding to ink keys in each ink well of the printing machine, wherein said image data has three color components, said representative color determining step being executed to classify pixels in each of said sections corresponding to ink keys according to tones of each of the three color components, and determine said representative color and a position thereof from pixels included in a predetermined class interval, wherein said representative color determining step is executed to create a histogram with the tones of each of the three color components of each pixel in each of said sections, and select the representative color and the position thereof from pixels included in a class interval of maximum frequency in said histogram, and wherein the position of the representative color selected is a position having a maximum area formed by the pixels included in said class interval.