对两幅灰度图像a,b的对应像素a(i,j)与b(i,j)进行算数运算（加、减、乘、除、乘方），结果存入c(i,j)。用户可以在五种运算中选择。-Two gray-scale images of a, b of the corresponding pixel a (i, j) and b (i, j) to carry out arithmetic (add, subtract, multiply, divide, involution), results into c (i, j) . User