- From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
- Date: Tue, 29 Jun 2010 15:04:46 +0200
- To: Alex Danilo <alex@abbra.com>, www-svg@w3.org
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: > > http://www.w3.org/TR/SVGCompositing/ > 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 module. Olaf
Received on Tuesday, 29 June 2010 13:07:07 UTC