Originally Posted by jsr
However, on the Amiga, nothing supports alpha channel, nor from hardware, neither from software. Besides, even if i would made a custom IFF chunk, which would contain the alpha data, i cannot expect existing software supporting it.
Simply there is no any point storing the alpha data.
It's true that there's absolutely no point in storing alpha channel in an IFF file, however, it may be useful to add some BMP out features. You could add an option to output the PNG as two BMP files: One 24bit for the RGB data, and one 8bit for the alpha data.
It's probably mostly useful for programmers, and if that PNG library you were talking about earlier is easy to use and capable enough, then such features are probably not worth the effort.