| 摘要 |
PURPOSE:To enable highly accurate testing of decoloration by forming histograms of image density of a reference printed matter and a printed matter to be tested, then, when the difference between the frequencies of a given density is not less than a first decoloration discrimination value, checking the density frequency difference for not only the given density but also the adjacent densities, and discriminating the condition under test as decoloration when the difference is not less than a second decoloration discrimination value. CONSTITUTION:An image on a reference card 1 is picked up by an ITV camera 3, and is subjected to A/D conversion at a converting part 41 in a main body 4 of a tester to be a multivalued image. The multivalued image is stored into a RAM 42, and a density histogram is formed by a calculating part 44. A density histogram for a card 1 to be tested is formed similarly to that for the reference card 1, and the calculating part 44 calculates the difference in frequency between the two density histograms on the basis of each density. When the difference for a given density value (n) is not less than a first decoloration discrimination value alpha, the difference in frequency is calculated for not only the given density value (n) but also the adjacent density values n-1 and n+1, and when the difference is not less than a second decoloration discrimination beta, it is judged that decoloration is present. It is thereby possible to automatize decoloration testing without errors and with high accuracy, through discriminating decoloration from effects of nonuniformity in illustration by a light source 6 or the like. |
