Converting Colors to Other Colors

I have to convert all non-red colors in an image to black, and then convert the red color to white. I am completely lost. Could anybody lead me in a direction? Thank you!

[Voss]

If you have this image stored as an image file, the first thing to do would be to read the file into a variable, e.g., using the imread function.

Answer 1

[jonas]

Load image

RGB = imread('image.png');

Image is stored as a nxmx3 matrix, where the 3 layers are red, green and blue pixel intensity and nxm is the resolution. Find pure red colors by finding the indices with strong red channels (1st layer close to 255) and weak green/blue channels (2nd and 3rd channels clsoe to zero).

mask = RGB(:,:,1)>230 & RGB(:,:,2)<1 & RGB(:,:,3)<1;

then you can use this mask to change the colors of your image

RGB(repmat(~mask,1,1,3)) = 0;
RGB(repmat(mask,1,1,3)) = 255;

imshow(RGB)