The basic concept for evaluating print quality using a mobile phone camera is as follows: The printed material must display a 3x3 grid of colors as shown in the image. The composition of these nine color blocks has been mentioned several times before: CMYK full coverage, CMYK 50%, and C50MY40 gray balance. The camera must distinguish the range of this grid, extract the RGB values, convert them to CIE system values, and then calculate values such as color difference, TV, and gray difference. Finally, a score is given based on the full-page color difference, TV difference, and the brightness and gray difference of the gray balance.