说明：  图像处理的几个函数：灰度变换、图片大小变化、直方图处理、中值滤波、锐化、拉普拉斯锐化、sobel锐化
(Several functions of image processing: gray-scale transformation, image size change, histogram processing, median filtering, sharpening, Laplace sharpening, sobel sharpening)