Watermark method aiming at computer graphic image

Abstract

The invention discloses a watermark method aiming at a computer graphic image. A watermark signal adopts a pseudo random sequence in spread spectrum communication and the sequence item takes a value from {-1,1}. The method comprises the steps of firstly performing contourlet transform on the image, embedding the watermark signal into a sub-band with the greatest energy in direction sub-bands of second level conversion in the contourlet transform, and performing contourlet inverse transform on the contourlet transform coefficient embedded with the watermark to obtain a watermark image; then performing contourlet transform on the watermark image, selecting the sub-band embedded with the watermark, taking the absolute value of the contourlet transform coefficient embedded with the watermark, modeling the absolute value and performing watermark detection in the absolute value domain. The watermark method overcomes the difficulty for accurately modeling the contourlet coefficient of the computer graphic image, so the success rate of the watermark detection is improved, the transparency and robustness of the watermark can be well balanced, the watermark detection does not relay on an original image and the effect is better than the effect of the detection carried out directly on a transform domain.

Description

Technical field [0001] The present invention involves a watermark method for computer graphics, which belongs to the field of information hidden technology. Background technique [0002] In the field of digital images (video) watermarks, people focus on natural images and ignore computer graphics image (CG), which is gradually becoming more and more popular and important information carriers.Simply transplant the watermark algorithm for natural images to be transplanted on the computer graphics image, which will cause obvious human traces, and it is easy to be perceived by the human vision system (HVS).It feels that the difference in this level is easily perceived by HVS, which makes it difficult to embed the watermark in CG images. [0003] Studies have found that HVS is less sensitive to the distortion of the edge of the image, and CG images are no exception. Therefore, watermarks can be considered into the edge of CG images.Contourlet transform (CT) is a transformation that is...

AI Technical Summary

Problems solved by technology

For the distribution of CT coefficients of CG images, due to the particularity of the distribution, the distribution characteristics cannot be well described when modeling with GGD, and the result is a decline in watermark detection performance.

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