How to use colormap

Hi everyone. I want to color in the letter 'a' from an image full of different characters. I have two images, one with the characters without the letter 'a'(call this A) and one with only the letter 'a'(call this B). I want to set the image B to the color red using colormap but not sure how to use this function in this situation.

Thanks for reading.

Answer 1

[Image Analyst]

Cast the images to single. Then subtract them and take the absolute value. Then threshold it

subtractedImage  = abs(single(imageA) - single(imageAwithLetter));
binaryImage = subtractedImage > thresholdValue;

Then create image B:

imageB = rgb2gray(imageA);  % or just imageA if imageA is already grayscale.
imageB(imageB == 255) = 254; % Set existing 255 to 254
imageB(binaryImage) = 255; % Set only the letter pixels to 255.
imshow(imageB);
myColormap = gray(256);
myColormap (256,:) = [1 0 0]; % 256 goes to pure red.
colormap(myColormap);
colorbar;

[u-will-neva-no]

Nice one, thanks!