Detecting Red Green and Blue by cancelling background - matlab

Question

I have continuous image acquisition and have a white paper at the background of the camera (facing the camera)
The image with just the white background is producing a greenish blue tinge due to light bulbs used in the room which is resulting in output as GREEN for the following code
green = im(:,:,2);
red = im(:,:,1);
if sum( green(:)) > sum(red(:))
disp('green');
else
disp('red');
end
Is there any way to CANCEL the white paper background for processing only the color objects that will be placed in front of the camera ??
The Color objects will be RED, GREEN and BLUE squares

Answer 1

The way you are testing for green or red is fundamentally flawed - you need to look for the dominant colour using a suitable threshold, otherwise you will get false positives. E.g.
threshold = 0.7; % determine a suitable threshold empirically
blue = sum(sum(im(:,:,3)));
green = sum(sum(im(:,:,2)));
red = sum(sum(im(:,:,1)));
total = red + green + blue;
if (red / total > threshold)
disp("red");
elseif (green / total > threshold)
disp("green");
elseif (blue / total > threshold)
disp("blue");
else
disp("indeterminate colour");
end