clipka wrote:
> Which hints at another problem with the new 3.7 behavior: It seems that this is
> dealt with in the backend; but a look at the PNG spec indicates that it is in
> fact a file-format dependent issue, and should therefore be handled in the
> frontend.
> 

This is not really an issue because almost all graphic file formats (and 
all supported by  POV-Ray) do only use non-premultiplied alpha channels 
just like described in the PNG specs. The only exceptions I'm aware of 
that do *also* support premultiplied alpha are TIFF (where a tag for 
this exists) and Microsofts DDS.
The only reason premultiplied alpha does exist at all is to save one 
multiplication per pixel when composing the image with the background, 
and so might have been important in the early days of computer graphics, 
especially games.

-Ive

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