Valid Digital Watermarking of Palette-based Image
Manchun Cai · Acta Scientiarum Naturalium Universitatis Sunyatseni · 2004
The palette_based image is widely used in practical, such as in internet and in mobile network. But there is little research on the palette_based image in digital watermark field, since in contrast with the true color image, the palette-based image has quantized color cube and independent color table. By analyzing the present digital watermark methods of palette_based image, disadvantages of them are pointed out in this paper. They are low validity, severe visual distortion and resistlessness to the palette analysis. A valid digital watermark method of palette_based image is proposed. The cluster analysis is used to reduce the visual distortion, and the embedding capacity is increased by using the grads modulation scheme which is presented. Then the raw message is embedded into or extracted from the palette_based image by adjusting the color frequencies of nearest pixels in image. On the premise of guaranteeing the image fidelity, the proposed method is perfect valid which means the bit error rate is almost zero. Furthermore, the method can resists attacks of the palette analysis, the format transformation and the copy_paste operation.