US Patent 7710612 Method of effacing zipper image

A method of effacing zipper image, applicable to scan a document by a scanner with a stagger charge-coupled device. The nth (n is a positive integer) pixel value obtained by scan on a scan line at which the zipper image is produced is subtracted by the (n+1)th pixel value obtained by scan on the scan line. The absolute value of the result is then compared to a critical value. If the result is smaller than the critical value, the nth pixel is modified by the method.