Apparatus for determining the soil degree of printed matter

A soil degree determining apparatus for determining soiling on printed matter, comprising:

• image input means for inputting an image of printed matter to be subjected to soiling determination,
• image extracting means for extracting image data in a particular area including a printed area, from the image input by the image input means,
• changed-section extracting means for extracting, on the basis of the image data in the particular area extracted by the image extracting means, a non-reversible changed section, thereby providing data concerning the non-reversible changed section,
• feature quantity extracting means for extracting a feature quantity indicative of a degree of non-reversible change in the particular area, on the basis of the data concerning the non-reversible changed section provided by the changed-section extracting means, and
• determining means for estimating the soil degree based on the feature quantity extracted by the feature quantity extracting means,
• wherein
• the image input means is adapted for inputting the image as an IR image using IR light having a near-infrared wavelength,
• the changed-section extracting means includes image emphasizing means adapted for emphasizing a wrinkle and/or a fold in the particular area caused when the printed matter is folded, thereby providing emphasized image data, and
• the changed-section extracting means is adapted for extracting the non-reversible changed section from the emphasized image data.