The mother phase image is transformed by discrete Fresnel diffraction transform, then the phase angles are withdrawn to form the phase encryption mask; the original watermark image is encrypted into the cipher text by the phase encrypted mask after DFDT; the original host image is transformed by DWT, the pixels of high frequency parts are modified with the encoded watermark under weight factor, which is replaced by the average of its adjacent four-pixel neighborhoods; finally, the watermarked image is obtained after inverse DWT.
通过提取相位母板的离散菲涅耳衍射变换的相角而获得相位密码板，原始水印图像经离散菲涅耳变换和相位密码板的共同作用形成水印密文，将水印密文嵌入到原始宿主图像的离散小波变换系数矩阵中，再对叠加水印信息的像素用其最邻近的像素均值来替换，从而获得一种新的盲数字水印提取法。