Updated the question and provided a specific case. I have a dataset of RGB images as well as the corresponding Alpha map images (which contain only black, 0.5, and white). I would like to import and concatenate the alpha maps with the RGB images to create a 4-channel RGBA input for the network. Currently, my code is creating a 6-channel input, presumably because it is concatenating RGB with RGB instead of RGB with A. How can I do this properly?