说明：  本源代码首先实现普通的直方图均衡化，再实现灰度级之间的均匀分布，可以有效的解决直方图均衡化过程中的灰度断层现象。使得图像更加的柔和，直方图分布更均匀。
(Source code first to achieve common histogram equalization, and then to achieve uniform distribution between gray levels can be an effective solution in the process of histogram equalization, gray fault phenomenon. Makes the image more of the soft histogram more evenly distributed.)