Re: [SVG1.1F2 LC] 15.12 Filter primitive 'feComposite' formula

Alex Danilo:
> Hello Olaf & Erik,
> 	We included all the Porter-Duff equations in the
> compositing chapter back around 2002 or so, and the current
> draft of that is at:

Looks like something easier to understand without further
searching ;o)

> 	I agree it would be good to include the actual equations
> in the spec. especially since I don't believe the original
> Porter-Duff paper took alpha into account IIRC.

The article deals with rgba images/pixels.
I think, this is sufficient, if we interprete the 
primitive filter inputs as rgba images/pixels.
The main thing one has to guess for SVG is,
how the pictures A and B in the article are related
to the inputs in and in2 of the filter primitive ;o)

But the article contains some other interesting information
as well, for example about premultiplication, a range for
the color values from 0 to 1 and something
like 'transparent black' or 'clear', not really defined in SVG 
properly, but used ;o)
At least for me the article helped to understand some more
or less opaque parts for the filter chapter of SVG ...
For me this indicates, that the wording and structure of the
filter chapter leaves room for improvements related to better
understandability for the general public ;o)
The heterogeneous  structure of sections and formulas 
indicates as well, that this is not really a literary masterpiece.
But I think a major improvement can be left to the new filter


Received on Tuesday, 29 June 2010 13:07:07 UTC