阐述了离散傅里叶算法(DFT)、离散余弦算法(DCT)、离散小波变换算法(DWT)这3种常用的频域数字水印算法的原理，并分别采用不同算法对数字图像进行了水印嵌入，检测其峰值信噪比(PSNR)和相关系数(NC)的值，分析并比较了这3种算法的优缺点，证明了离散小波变换在频域算法中能够得到最好的效果。

The principles of three commonly frequency domain digital watermarking algorithms were introduced, of which were discrete Fourier transform algorithm (DFT), discrete cosine transform algorithm (DCT), and discrete wavelet transform (DWT). Digital watermark information was embedded into the carrier image with the three algorithms. The values of peak signal-noise ratio (PSNR) and correlation coefficient (NC) were detected. The advantages and disadvantages of the three algorithms were analyzed and compared. It was proved that DWT algorithm can get the best effect.