Suppression of moire patterns in scanned halftone images

Moire patterns often appear in the image obtained from scanning an image pr inted on a magazine or a newspaper. The patterns do not exist in the origin al printing but come from alias sampling of screened halftone pictures. A s trategy to design a moire suppression scanning procedure is proposed. Fouri er analysis is presented for both the screening and the scanning processes, from which a formula is derived to calculate a special scanning resolution , called moire controlling scanning resolution. With the moire scanning res olution, an input halftone image is scanned and the moire signals can be co nfined in programmed frequency areas. After filtering out the signals in th ose areas, the original can be restored. Some useful spatial filters for th is purpose are designed. Experimental results are shown to demonstrate the feasibility of the proposed approach. (C) 1998 Elsevier Science B.V. All ri ghts reserved.