GrayImage = imread(‘c:/users/mat/c1.jpg’);
[rows , cols] = size(GrayImage);%得到图像矩阵的行、列数
ZhiFang = zeros(1 , 256);%初始化一个矩阵，用来存储灰度图像中每个像素出现的频率
for i = 0:255
ZhiFang(1 , i+1) = length(find(GrayImage == i)) / (rows * cols);%计算矩阵GrayImage中值与i相等的元素的个数
end
figure(1);
bar(0:255 , ZhiFang , ‘grouped’);%根据bar绘制直方图
xlabel(‘灰度值’);
ylabel(‘出现次数’);
axis([0 255 0 0.02]);%axis函数用来设置画面横坐标及纵坐标的上下限