I have a BMP image without an alpha channel. For a game texture, I would like to add a "mask map" which is a black / white image which tells which regions should be transparent.
To do this, I first opened the BMP image and added a new channel to it and called it Alpha.
Then I opened the mask image, pressed Ctrl A to select everything and copied it.
Then back to the RGB image, I de-ticked the eyes for each channel except the Alpha channel.
Then I pasted the copied image.
However, I don't see any change in the resulting image when I enable the eyes of each channel.
How could I achieve this in the proper way?