Quote Originally Posted by cragwolf
Since you want it to work on Win32, Linux and MacOS X, you're clearly looking for a Free Pascal solution, so Kylix and Delphi support is irrelevant. Doesn't Free Pascal support PNG with the fpimage unit? I haven't tried it outside of compiling and running the associated demo program (see imgconv.pp), but it seems to support transparency as far as I can tell. Also, as far as I can tell it doesn't require libpng, but correct me if I'm wrong. It's part of the FCL, which is poorly documented. You'll have to look at the source code to see what it can do. It's in the fcl/image sub-directory.
I compile my programs on win32 with delphi, and kylix on other platforms, since so far, delphi still leads the performance for code execution on win32.