彩色图转化成灰度图

加权法就是  GRAY==0.3*R+0.59*G+0.11*B

均值法就是 GRAY==(R+G+B)/3

最大值发就是  max（R,G,B）

A=imread(‘D:\lena.BMP‘);
r=double(A(:,:,1));
g=double(A(:,:,2));
b=double(A(:,:,3));
[m,n]=size(r);
bw=zeros(m,n);
bw=0.3.*r+0.59.*g+0.11.*b;
subplot(2,2,1)
imshow(mat2gray(bw));
title(‘加权法，其实我们的rgb2gray就是默认的加权法‘)
bw1=zeros(m,n);
bw1=(r+g+b)./3;
subplot(2,2,2)
imshow(mat2gray(bw1));
title(‘均值法‘)
bw2=zeros(m,n);
for i=1:m
    for j=1:n
       bw2(i,j)=max(max(r(i,j),g(i,j)),b(i,j));
    end
end
subplot(2,2,3)
imshow(mat2gray(bw2));
title(‘最大值法‘)