Correct me if I'm wrong, but neither Delphi nor Kylix work on MacOS X. So I think I made a reasonable assumption in concentrating the discussion on Free Pascal, which does work on MacOS X. Also I just noticed that this is the Free Pascal forum. I should read more carefully. ops:

Anyway, I did some testing with the fpImage unit, and found that while it does support the reading of alpha channel information from PNG files, it crashes when you try to write such information. Writing is fine when you don't have an alpha channel. I submitted it as a bug to the FPC guys.

Personally, I stick with TGA files. This image format is so simple that even someone as dumb as me can create a reader/writer class for it. Compression tends to be 2 or 3 times worse than PNG but I can live with that.