直方图均衡：原始图的直方图变换为均匀分布的形式，这样就增加了象素灰度值的动态范围从而达到增强对比度的效果

中值滤波：中值滤波属于非线性平滑滤波器，它可以消除噪声又能保护图象的细节-histogram equalization : the original plan to transform the histogram in the form of uniform distribution. This will increase the value of the pixel gray areas so as to achieve dynamic contrast enhanced effect of filtering : Median filter is nonlinear smoothing filter, it can eliminate noise while preserving image details