Ive, it appears to me that TIFF is handling the alpha channel different
from other file formats; something about "precomputed alpha" I guess -
is that right?
clipka wrote:
> Ive, it appears to me that TIFF is handling the alpha channel different > from other file formats; something about "precomputed alpha" I guess - > is that right?
TIFF supports *everything* and so the image data itself might already be
"pre-multiplied" by the alpha channel or it might not (like within PNG)
which should nowadays be the more common case (but TIFF exists since
over 25 years!).
The libtif-RGBA-interface does not care about such things and (as I've
tried to explain in some of my other posts) even the way the meaning of
the tag that does specify this has changed over the years.
Also the RGBA-interface returns just the first of possible multiple
"extra"-channels and the actual alpha channel could also be e.g. the
second one.
Not to mention that the returned A-channel might be no alpha channel at
all, could be anything, e.g. a depth-map. And it can also happen...
...am I starting to bore you? Just tell me!
-Ive
Ive schrieb:
> Not to mention that the returned A-channel might be no alpha channel at > all, could be anything, e.g. a depth-map. And it can also happen...> ...am I starting to bore you? Just tell me!
I'm not easy to bore, but... well, I guess I'll just file the TIFF
format as "too flexible to bother about the details at present" :-P
