Patent ID: 7006256

Claim:
A watermarked image generator that embeds watermarks into an input image to generate a watermarked output image, comprising: a watermark data source that inputs watermark data to a watermark embedding device, the watermark embedding device halftoning the input image to generate the output image made of 2×2 binary patterns, the 2×2 binary patterns forming the watermarks embedded in the output image, wherein the watermark embedding device includes: a tri-level error diffusion generator that performs tri-level error diffusion on a reduced resolution version of the input image by halftoning the input image into black, white and 50% gray; and a plurality of halftoning circuits that successively replace each pixel of the halftoned input image with one of a plurality of the 2×2 binary patterns, the one of the plurality of 2×2 binary patterns being selected based on at least one bit of the watermark data when a pixel of the halftoned image data is 50% gray.