For enhancing printing images quality so as to meet human visual needs, two ways of scanners clarity compensating by optical unsharp-mask and electronic second differential had been devoted based on investigating the cause of cut down on presswork definition produced by printing, the advantages of the twofold method which combine the two was also discussed in the thesis. The method of applying the technique was proposed in digital image processing. Tests had been done on standard images by the suggested method in Matlab, normal ways of USM and second differential were also used for comparing, printing proofs were made after manipulation for subjective evaluation on sharpening degree, statistic analysis on assessment data was also made, which shows that: the second differential method will bring the highest clarity on images with the side-effect of too heavy edges, USM can get relative mild margins and slightly lacking of distinct, the twofold method get preferable contour strengthen and smoothness, it can be used in printing image sharpening.
Unsharp Mask Guided Filtering
