读取rgba格式的图片，并且显示R分量成灰度图

clear all;
mFID = fopen(‘C:\Users\WDJR\Desktop\r.txt’, ‘r’);
y=textscan(mFID, '%d ')
y=cell2mat(y);
m=reshape(y,19204,1080);
% m=m’;
figure(1);
colormap(gray(256));
image(m);
ii=0;jj=0;
for i=1:4:19204
ii=ii+1;
for j=1:1:1080
jj=jj+1;
z(jj,ii)= m(i,j);
end
jj=0;
end
figure(2);
colormap(gray(256));
image(z);

结果：读取r分量并且显示