TIFF and LibTiff Mail List Archive

2000.07.31 22:49 "Readiing Photoshop Alpha in library", by Phil Weeks

Subject pretty much says it all. How do you do this? We save tiffs from photoshop, should be 32 bit rgba tiffs, when read by tiffinfo, it reports back that there is extra samples, but it is unspecified. If this file is read into Paint Shop Pro, and resaved, tiffinfo correctly reports the extra sample as assoc-alpha. Looking inside the debugger of the tool I've written that uses libtiff, when the photoshop file is read in the alpha is all 255 (0xFF), obviously not what I want. So the question is, how do you get the alpha read from a Photoshop tiff file?