说明：  数字水印的嵌入与提取算法有多种多样，那怎样评价数字水印嵌入效果和提取效果的好坏呢？业界是这样评价的：针对嵌入效果，我们用峰值信噪比（PSNR）进行评价，数值越大嵌入效果越好。
(There are many kinds of embedding and extracting algorithms of digital watermarking. How to evaluate the embedding and extracting effect of digital watermarking? This is how the industry evaluates: for the embedding effect, we use peak signal-to-noise ratio (PSNR) to evaluate, the larger the value, the better the embedding effect.)