Thanks for the help! At first, I had just 1 binary mask. I got 2 more and I want to combine/format all 3 into a single mask that can be used as ground truth (so I can segment more things with just one model). The training image has a shape of (3, 224, 224) and each mask has a shape of (1, 224, 224). What should be the shape of the combined formatted mask and what values should it contain? How can I achieve that?