图像平滑是数字图像处理的一个重要内容。我们所涉及的图像中、相邻象素的灰度之间大多具有很高的相关性，也就是说一幅图像中大多数象素的灰度值差别不大。因为这种灰度相关性的存在，一般图像的能量主要集中在低频区域中，只有图像的细节部分的能量才处于高频区域中。但因为在数字化和传输过程中经常有噪声和假轮廓出现，这部分信息也集中于高频区域内。-Image Smoothing of digital image processing is an important element. We are involved in image between the adjacent pixel gray mostly with a very high correlation, meaning that the majority of image pixel gray value is not very different. Because the gray-scale correlation exists, the general image of energy mainly concentrated in the low-frequency region, only the details of the image part of the energy only in the high-frequency region. However, because in the digitization and transmission of noise and often leave the outline of the emergence of this part of information is also concentrated in the high-frequency region.