Ugh, no, I replied to the wrong email. Just ignore what I said.

> On Jun 24, 2016, at 10:43 PM, Larry Gritz <[email protected]> wrote:
> 
> For those following along at home, Michel and I have been discussing this 
> off-list, and thanks to his investigation, it turns out that the real issue 
> is explained and fixed with this patch:
> 
> https://github.com/OpenImageIO/oiio/pull/1441
> 
> 
> 
>> On Jun 23, 2016, at 1:36 AM, Michel Lerenard <[email protected]> wrote:
>> 
>> 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
>> 
> 
> --
> Larry Gritz
> [email protected]
> 
> 

--
Larry Gritz
[email protected]


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