How do I read an arbitrary chunk from a PNG file?
- by Mason Wheeler
I've got some custom metadata to put into a PNG file. It's being saved through libpng, and it's not difficult to write out a custom chunk. I just call png_write_chunk with the name, length and data. But I can't see how to get the data back out again. I'd expect there to be a png_read_chunk function that takes a chunk name and returns a pointer to the data or something like that, but there's nothing like that in png.h.
Does anyone know how to accomplish this?