how to transfer one shape onto another

[liamlars]

I need to be able to edit digital images, in following way: original image depicts some object which is not flat. It could be for example a curtain that is hanging disorderly down the window, or a wrinkled tablecloth, or somebody's discarded jeans (mostly, fabrics, hanging loosely or being discarded in a heap). I have another image, of an object which is flat, two dimensional. For example, a drawing of a rose. Or a butterfly. Stuff like that. And I need to transfer this image to the first object in a way that will make it look like it was always there. That is, the otherwise white curtain needs to look like it has roses all over it, jeans need to look like they have various butterflies on them, etc. So, I need the way to capture the shape of the first object, and then to apply the same curvature on my new objects before or during placement. I understand how to do basic image manipulations in Gimp, but the above is really above my pay grade. Could somebody please tell me which tutorial and which part of it deals with that kind of issue? Or point me in the right direction in some other way? Thanks