Hi,
A while ago, I had an issue with single channel tiff files ( crash in
alpha premult ), which I fixed by setting
"oiio:UnassociatedAlpha" = 1 in the spec config.
Weird thing is, I kept getting crashes with another file that declares
multiple channels, in the same premult function.
In my code, I read channel by channel, so I have multiple calls to
TIFFInput::read_scanline, with chbegin = chend each time.
After a bit of debug, I found that the first time I call the function,
the m_convert_alpha boolean is correctly set to false. However, in the
second call, it get erased in ImageInput::read_scanlines and is set to true.
The issue comes from the way the read_native_scanline function is coded:
if we request a scanline that we have already read, we close the file
and reopened it using this calls:
if (! close () ||
! open (m_filename, dummyspec) ||
! seek_subimage (old_subimage, old_miplevel, dummyspec)) {
return false; // Somehow, the re-open failed
}
So obviously, the current config paremeters are lost. Isn't it possible
rewind instead of reopening the file ?
Second question: can the premult work when reading channel per channel ?
Naively I'd say that it can't: we may not have the data in memory.
Michel
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