一般的图像增强方法根据增强处理过程所在的空间不同，可分为基于空域和频域的方法。基于空域的方法直接对图像进行处理；基于频域的方法是在图像的某种变换域内对图像的变换系数进行修正，然后再反变换到原来的空域，得到增强的图像。(Generally, image enhancement methods can be divided into spatial and frequency domain methods according to the spatial difference of the enhancement process. The method based on spatial domain directly processes the image; the method based on frequency domain corrects the transform coefficients of the image in some transform domain, and then inversely transforms them into the original spatial domain to obtain the enhanced image.)