说明：  包括画单图的直方图，均衡直方图，归一化直方图以及两幅图像的联合直方图；修正了读入图像时要在同一目录下、以及图像的格式和是否为RGB图像的限制；修正了画两幅图像联合直方图时，大小需要保持一致的限制
(Paintings include single graph histogram, histogram equalization, the normalized image histogram and two joint histogram amended to read into the images in the same directory, and image formats and whether the restrictions RGB images Fixed painting two joint histogram, the need to maintain a consistent size restrictions)