I have a problem for which i haven't found a solution in GIMP, but I'm
sure there is some easy way to achieve this.
I have a 24-bit image file and a separate 256-gray-level image of the
same size. The gray-level image is supposed to act as the alpha channel
for the 24-bit image. I managed to transfer the gray-level information
into the alpha channel of the grey image, and then switched the image
mode from 256 gray levels to full RGB. Then I just selected the other
24-bit image and copied and pasted it into the modified gray level
image. My idea was that, as the original 24-bit image does not have an
alpha channel, the copy/paste would transfer the R, G, and B channels
but leave the alpha channel as it was. Unfortunately, pasting the other
24-bit image also replaced the contents of the alpha channel with a 100%
So, how can I apply a separate 8-bit gray-level image as the alpha
channel for a 24-bit RGB image of the same size?
Thanks in advance,
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