Converting location into binary masks and filtering the image with such masks

Question

Say that we have an image which pixels were labeled 1 and 2. How can we do the following in MATLAB?

• Convert the locations of 1s and 2s into binary masks
• Filter the image with those masks

Thanks.

Answer 1

Example:

% some RGB image
img = im2double(imread('peppers.png'));
[h,w,~] = size(img);

% lets create some random labels. I'm simply dividing into two halves,
% where upper half is labeled 1, and lower half labeled 2
labels = [ones(h/2,w)*1; ones(h/2,w)*2];

% compute masks and filter image using each
img1 = bsxfun(@times, img, labels==1);
img2 = bsxfun(@times, img, labels==2);

% show result
subplot(121), imshow(img1)
subplot(122), imshow(img2)