Apparatus for examining the degree of stain on printed matter

An apparatus for examining the degree of stain on printed matter, comprising:

• image input means for inputting images including the image of printed matter to be examined and supplying image data on the printed matter;
• area information storage means for storing positional information on at least two target areas on a standard image corresponding to said image of the printed matter, the area of each of the target areas, their standard average densities, and the degree of dispersion in their density distribution;
• average density computing means for calculating the average density for each target area in said image data supplied from said image input means by using the positional information on each target area and the area of each target area supplied from said area information storage means;
• density difference measuring means for measuring the density difference between the average density for each target area calculated by said average density computing means and said standard average density for each target area supplied from said area information storage means;
• density difference normalizing means for normalizing the density difference for each target area by using the density difference for each target area measured at said density difference measuring means and the degree of dispersion in the density distribution for each target area supplied from said area information storage means;
• and
• summing means for summing the normalized density difference for each of said target areas supplied from said density difference normalizing means and thereby judging the degree of stain on said printed matter to be examined.