为提高水印抗印刷/扫描攻击的鲁棒性,比较了在CMYK与RGB颜色空间嵌入的水印经印刷/扫描后提取的效果。采用离散小波变换域傅里叶全息数字水印算法生成水印图像,经印刷/扫描后,可以提取到水印;然而,由于印刷/扫描过程中颜色空间的转换,使得原本嵌入某一颜色通道的水印转移到其他通道,降低了单通道提取的水印质量;且相对于RGB颜色空间,在CMYK颜色空间嵌入水印生成的水印图像经历印刷/扫描后提取到的水印质量普遍较高,说明CMYK→RGB→CMYK颜色空间的转换相对于RGB→CMYK→RGB颜色空间的转换,对水印图像的改变较小。为减小印刷/扫描攻击的影响,考虑下一步研究工作主要集中在CMYK颜色空间嵌入水印。
In order to find the proper color space for promoting robustness against print-and-scan, the watermarks extracted from watermarked image embedded into CMYK and RGB color space were compared. Experiments showed that the watermark embedded into one channel diffused to other channels and reduced the quality of extracted watermark. The watermark extracted from watermarked image embedded into CMYK color space had higher quality than RGB space, which indicated that the transformation of CMYK → RGB → CMYK led to less damage for extracted watermark than in the transformation of RGB→CMYK→RGB. The future research on anti-counterfeiting print should mainly be focused on the embedded watermark CMYK color space.