Method for automatic trap selection for correcting for plate misregistration in color printing

Abstract

A method for automatic compensation for misregistration of printing plates in printing of polychromatic document pages or images, in which a trapping map image is superimposed upon the structured graphic image representing the layout of the document page or image from which it is derived, so as to prevent light leaks and other errors at the boundaries between color regions within the image. Traps are selected automatically and applied to a boundary map comprising the set of boundaries between regions of different color of the original image. The selection process uses the results of a plurality of separate methods for ranking possible traps each of which is assigned an overall score by means of a weighted sum of the ranks obtained by each of the separate methods, with the resulting score used as the basis for automatic trap selection among the set of possible traps. The weights applicable to the score are previously determined according to several methods, such as a least squares fit procedure in which traps are judged subjectively by "experts" and correlated with the ranks obtained by each of the separate methods.

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