i don't want to extract or use the multi-layer information, i want to report to the user that it can't be imported. i'm creating specific-sized jpgs from imported files, and the user needs to decide how to flatten that multiple-layered file according to her aesthetic.
the only reference to multilayered i see is CGImageSourceGetCount(CGImageSourceRef)
If the image source is a multilayered PSD file, the function returns 1.
which, of course, isn't helpful in my case.
From my own searching, you can't do this with ImageIO. The only way I've found to deal with multi-layer images is with the QuickTime image importers. See this link: