MATLAB: Image processing using indexing

colormapimage processingindexingrgb

Hi. I am wondering if anyone can help me. I'm not sure wether this is possible but i will try to explain it as best I can.
I have two images with the same resolution.
Image A, a RGB image.
Image B, a Gray scale image the with only a small region of postive values the rest black (0 values).
I wish to map a jet colormap to Image B and substitute these potive pixels into image A (repleaceing the pixels from A)
I understand that a grayscale image with a colormap is of a different format to a RGB image which is (m*n*3). But is it possible.
I hope i have explained it clearly enough.
I would be gratefull for any help. Thank you
Regards Dana

Best Answer

The details depend on what class your images are, but here's an example that you can probably modify as needed.
% test data - an rgb image and a greyscale image the same size, with lots
% of zeros in it
A = imread('saturn.png');
p = imread('pout.tif');
B = zeros(size(A,1), size(A,2), class(p));
B(1001:1000+size(p,1), 501:500+size(p,2)) = p;
% apply the jet map to the greyscale image
if strcmp(class(B), 'double')
  % assume values in range 0-1
  Brgb = ind2rgb(B, jet);
else
  nvals = double(intmax(class(B))) + 1;
  Brgb = ind2rgb(B, nvals*jet(nvals));
end
% copy non-zero parts of B into A
ind = repmat(B ~= 0, [1 1 3]);   % index array
Amod = A;
Amod(ind) = Brgb(ind);
% look at the result
imshow(Amod);
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