如果一副图像的像素占有很多的灰度级而且分布均匀，那么这样的图像往往有高对比度和多变的灰度色调。直方图均衡化就是一种能仅靠输入图像直方图信息自动达到这种效果的变换函数。它的基本思想是对图像中像素个数多的灰度级进行展宽，而对图像中像素个数少的灰度进行压缩，从而扩展像原取值的动态范围，提高了对比度和灰度色调的变化，使图像更加清晰。-If an image pixel occupies a lot of gray level and evenly distributed, so such images tend to have high contrast and varying shades of gray. Histogram equalization is a kind of input image histogram information alone can automatically achieve this effect transformation function. Its basic idea is the number of pixels in an image more gray-level broadening, while the number of pixels in the image of a small gray compress like to extend the dynamic range of the original value, improved contrast and gray tones changes to make the image clearer.