测试代码如下：
b=imread('CT.tif');
ming=min(b(:))
maxg=max(b(:))
total_b_n = sum(length(b(:)))
[pxy,xb]=imhist(b);
total_pxy_n = sum(pxy)
[m1,n1]=size(b);
total_b_n1 = m1*n1ming =
0
maxg =
255
total_b_n =
262144
total_pxy_n =
262144
total_b_n1 =
262144结果表明：imhist函数输出的pxy总和即为图片的数据个数