灰度图像转彩色图像 gray2rgb

img = imread('mdb025.jpg');
[rows,cols]=size(img);
 r=zeros(rows,cols);
 g=zeros(rows,cols);
 b=zeros(rows,cols);
 r=double(img);
 g=double(img);
 b=double(img);
 rgb=cat(3,r,g,b);
 imwrite(uint8(rgb),'mdb025-rgb.jpg');