knownbugs.txt

这是VCF框架的代码

Known bugs for FreeImage

- PHOTOSHOP AND ALPHA-CHANNELED TIFF ------------------------------------

LibTIFF doesn't load the alpha channel when that file is created
with Adobe Photoshop. This is a bug in Photoshop as it writes
the TIFF in a non-standard, non-documented way. According to
the LibTIFF mailing list:

"Photoshop's PSD file format allows for a number of layers, alpha
channels, etc. In such a sceme, there is no such thing as a single alpha
channel, but only a number of channels, some of which represent colors
in layers, or in a global picture, others alpha's that can have just
about any local layers or global image meaning and must even considered
to be editable and enablable/disablable by users all the time. I guess
this makes adobe reluctant to define such a thing as a single alpha
channel, including when they write out other formats that allow for
something else/more than a single alpha."

On the same libTIFF mailing a semi-solution is provided:

"If I create a 32-bit (24-bit + 8 bit alpha) TGA image in another
program, and load it into Photoshop, Photoshop shows it as RGBA.
If I then save it to TIFF, Photoshop properly flags it as an Alpha
channel, and TIFFReadRGBAImage reads it fine. I'm not sure what
Photoshop does differently when you create an Alpha channel by hand
versus loading it with the image."