Patent ID: 7889390

Claim:
An image forming method for digitally reproducing a moiré-free color: halftone image having an embedded correlation-based digital watermark using an enhanced halftone screen set consisting of a halftone screen for each of N colorants forming N color separations (where N≧3), the method comprising: providing a color input image to be watermarked; providing a watermark image to be embedded in the N-color image; generating N different uniform rosette halftone screen configurations each meeting uniform rosette halftone screen conditions; generating N three-dimensional threshold arrays each having a phase shift value as an input; and halftoning the color input image by halftoning N different color separations using a different one of the halftone screen configurations and three-dimensional threshold arrays for each color separation to produce a moiré-free color output image having the watermark image embedded therein.