How I can change white color to red?

I have an image and I would like to turn all white pixels to red. How can I do this?

Thanks

"I have an image" is not clear. Is it an oilpainting, an indexed grayscale image as PNG, or an imported RGB array?

Is a RGB image.

Answer 1

Let me guess what your image is:

img     = uint8(rand(640, 480, 3) * 255);
R       = img(:, :, 1);
G       = img(:, :, 2);
B       = img(:, :, 3);
isWhite = R == 255 & B == 255 & G == 255;
G(isWhite) = 0;
B(isWhite) = 0;
newImg  = cat(3, R, G, B);

I do not like this solution. Is there an "inplace" method which does not duplicate the data?

Thanks

Is (253,254,251) still white? (BTW, that's what my response was asking.) If so, you can alter the formula to use different thresholds. In that example, you'd use >= instead of == and the new threshold values:

isWhite = R >= 253 & G >= 254 & B >= 251;

Answer 2

Define the range of values that encompass white? Is it only (255,255,255) or could it be more of the possible 16.7 million colors?