关键词: 数字水印, 分形变换, 对比度因子

Abstract: It is necessary to study those watermark algorithms appropriate to the special feature of fractal transform. By analyzing related parameters in the process of image fractal transform and taking some trials, a new watermark algorithm embedding and extracting the watermark information was proposed by modulating the parameter of contrast factor which mapped the domain blocks to their best matched blocks in fractal transformation. Higher watermark capacity could be embedded into image at low algorithm complexity without having perceptible influence on the quality of the image. The extraction algorithm avoided the loss of watermark information because of the missed synchronization between original image and watermarked image, which improved the accuracy in extraction. Experiment results show the effectiveness of the algorithm.

Key words: watermark, fractal transform, contrast factor