Patent ID: 8351644

Claim:
A system for hiding secret data in halftone images, comprising: an image input module, executed on a processor, reading an original image data and a secret image data; a halftoning processing module coupled to the image input module, executed on the processor, receiving the original image data and the secret image data, performing a first error diffusion process to the original image to generate a first halftone image and performing a second error diffusion process to the original image data and the secret image data to generate a second halftone image; and an image output module coupled to the halftoning processing module, executed on the processor, outputting the first halftone image and the second halftone image, wherein the second error diffusion process comprises adding or subtracting a variable noise strength to or from each pixel of the secret image and wherein the halftoning processing module further comprises a noise strength determination module for providing the variable noise strength to be added to each pixel of the second halftone image, wherein the noise strength determination module receives the original image, calculates a corresponding variance for each pixel of the original image and obtains the variable noise strength for each pixel by searching a look-up table with the calculated variance for each pixel and the halftoning processing module further comprises: a first noise adjustment module coupled to the noise strength determination module for adding or subtracting the corresponding variable noise strength from or to each pixel according to pixel values of the first halftone image and pixel values of the secret image; a quantizor coupled to the first noise adjustment module for generating the second halftone image according to a predetermined threshold; and a second noise adjustment module coupled to the quantizor for subtracting or adding the corresponding variable noise strength from or to each pixel in response to the first noise adjustment module.