?? Index exceeds matrix dimensions.

Please can any body tell me whats wrong with my code? Its giving error on the 'If' statement. '??? Index exceeds matrix dimensions.'

function color()
img = imread('peppers.png');
r = img(:,:,1);
g = img(:,:,2);
b = img(:,:,3);
[m n] = size(img);

for i = 1:m
    for j = 1:n
        if ((r(i,j) - g(i,j)) >= 200) %&& mod(r(i,j) - b(i,j)) >= 200)
            im = r(i,j);
        else
            im = 0;
        end
    end
end
imshow(im);

[Fangjun Jiang]

Don't use color as the function name. Strange enough, help color and doc color give me different type of function help.

Answer 1

[Jan]

img = rand(2,3,4);
[m n] = size(img);

Now m is 2 as expected, but n is 12, the product of all trailing dimensions. Either use:

[m, n, dummy] = size(img);

or

[m, n] = size(r);

The program overwrite im in each iteration. I assume you want to set im(i,j) instead.

A more efficient approach without a loop:

r = img(:, :, 1);
g = img(:, :, 2);
im = r;
im(r - g > 200) = 0;