It can be accomplished in spatial domain and frequency domain. This chapter presents the ways of the smoothing of digital image.

数字图像平滑处理可以在空间域或频率域中进行。

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Directional smoothing filter is frequently used in digital image processing for it has the double properties of noise filtering and edge preserving.

方向平滑滤波器兼有去噪和边缘保持的双重特性，在数字图像预处理中被经常采用。

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