Patent ID: 8179570

Claim:
A method of generating an ultraviolet (UV) fluorescent watermark in an image, comprising: selecting an electronic continuous-tone color image in an input color space for a document; generating a binary watermark mask that divides the continuous-tone color image into two regions including a watermark region and a background region; performing a first color transformation that converts the continuous-tone color image in the watermark region from the input color space to a first CMY color space; executing a successive-filling halftoning algorithm with a dot-on-dot strategy on the continuous-tone color image in the watermark region to generate a first binary output image in the watermark region; performing a second color transformation that converts the continuous-tone color image in the background region from the input color space to a second CMY color space; executing a successive-filling halftoning algorithm with a dot-off-dot strategy on the continuous-tone color image in the background region to generate a second binary output image in the background region; generating a watermarked binary output image embedded with UV fluorescent watermark by combining the first binary output image in the watermark region with the second binary output image in the background region; and printing the watermarked binary output image on a fluorescent substrate.