| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method and system for halftone image watermarking. <P>SOLUTION: One method for halftone image watermarking assigns halftone watermark dot values to pseudorandom locations in an image and diffuses the error (106) of the watermark to neighboring pixel locations of these dots. Another method modulates halftone thresholds to convert multilevel pixels to watermarked halftone pixels. This method may be used in conjunction with a robust watermark (110) spread throughout the image before embedding the halftone watermark. In a compatible watermark reader (124), digital watermark signal strength is measured by analyzing bit errors in the extracted watermark message signal. <P>COPYRIGHT: (C)2007,JPO&INPIT |
