基于离散小波变换的差分能量水印技术

DIFFERENTIAL ENERGY WATERMARKING BASED ON DISCRETE WAVELET TRANSFORM

经典差分能量水印是基于离散余弦变换(DCT)的水印技术,为了使该水印在离散小波变换(DWT)域实现,提出一种基于DWT域的差分能量水印技术。首先通过选取DWT子带系数构成类似于DCT块的DWT块,由于差分能量水印方法在嵌入水印时建立局部能量差,检测时根据这能量差检测水印。其次,为了阻止局部能量差的消失,在保证视觉质量不受影响的情况下,适当地增加一个子区的能量,能有效降低加水印图像经过JPEG压缩后的水印检测比特差错率。对量化因子对图像质量的影响进行一些分析,并与文献方法的抗压缩攻击的鲁棒性进行比较。实验结果表明该方法是有效的。

Classic differential energy watermarking （DEW） is the watermarking technique based on discrete cosine transformation （DCT）. In order to implement it in discrete wavelet transform （DWT） domain, we present a DWT-based differential energy watermarking. First, we choose the coefficients of DWT sub-band to form the DWT blocks which are similar to the DCT blocks. As the local energy difference is created by DEW when the watermark is embedded, the watermark will be detected according to this local energy difference. Then, in order to prevent the local energy difference from disappearance, the energy of a sub-region is properly increased to ensure that the bit error rate in image detection can effectively drop a lot after the JPEG compression on the watermark-embedded image under the condition of ensuring good visual quality of the image. The impact of the quantisation factor on image quality is analysed to a certain extent in the paper, and is compared with the robustness of anti-compression attack methods in literatures as well. Experimental results show that our method is effective.