用matlab函数实现给定图像的直方图；函数histeq()实现直方图均衡化；对给定图像，各自指定直方图，进行直方图匹配，使图像增强。这是个模板-Implemented by matlab function to a given image histogram　function histeq () to achieve histogram equalization　for a given image, each designated histogram, histogram matching, image enhancement. This is a template