说明：   首先读入图像，得到RGB3个分量，然后对三个分量分别作直方图均衡化，最后合成三个分量返回到RGB图，但是这种方法割裂了RGB3种颜色的相互关系
(First read in the image, to get RGB3 components, then the three components of histogram equalization, the final synthesis of the three components of return to RGB chart, but this method separates the mutual relations of RGB3 colors. )