Apply mask to images

Mask an Image

[MrGecko]

How could I use GD library to apply a mask to an image?
I have two images. one that is the mask and a jpg that I want to make transparent with the mask.

Thanks,
Mr. Geckp

[jatar_k]

no clue, my thought would be to pick through these

[libgd.org...]
[php.net...]