by Isick on Thu May 31, 2007 1:29 am
It depends on the effect you are going for. What I would do (if this is indeed the style you want) is to place the image in a layer of its own and a greyscale image of a footprint over it (also in its own layer). Then, by hand, select the depressed design created by the sole of the shoe, Inverse the selection (Ctrl + I) and, highlighting the image layer, delete what is selected.
What you should be left with is your image minus any part that was not in the depressed areas of the foot print.