On 04.07.2010 12:24, clipka wrote:
> Some other image file formats, such as OpenEXR and TIFF, officially use
> associated - or premultiplied - alpha, which means that the data is
> stored in the file already pre-composed against a black background, so
> simply ignoring alpha would indeed give what you'd expect.


To clarify and to prevent a new bug within POV-Ray:

I do not know where you did get the information/impression that TIFF 
"officially use associated - or premultiplied - alpha". This is not true 
as TIFF allows *everything*.
You might have misread the TIFF 6.0 specs section 18: Associated Alpha 
Handling. This section applies only *IF* the "ExtraSamples" tag is 
present and the value of the tag reads 1. In most cases (in all if the 
TIFF was written by any Adobe software) the value of the ExtraSample tag 
will be 0 - i.e. unassociated, non-pre-multiplied, straight.

-Ive

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