Wavelet based halftone segmentation and descreening filter design

The advent of electronic publication creates strong interest in converting existing printed documents into electronic formats. During this process, image reproduction problems can occur due to the formation of Moire patterns in the screened halftone areas. Therefore, the optimal quality of a scanned document is achieved if halftone regions are first identified and processed separately. We propose a complete algorithm to achieve this objective. A wavelet based halftone segmentation algorithm is first designed to locate possible halftone regions using a decision function. We then introduce a suboptimal FIR descreening filter to efficiently handle various screening frequencies and angles. Experimental results are offered to illustrate the performance of our algorithm.