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ISSUE-2343: 15.12 Filter primitive ‘feComposite’ formula [SVG 1.1 F2 Last Call]

From: SVG Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Tue, 29 Jun 2010 13:35:48 +0000
To: public-svg-wg@w3.org
Message-Id: <E1OTaya-0006be-3o@stu.w3.org>

ISSUE-2343: 15.12 Filter primitive ‘feComposite’ formula [SVG 1.1 F2  Last Call]

http://www.w3.org/Graphics/SVG/WG/track/issues/2343

Raised by: Erik Dahlström
On product: SVG 1.1 F2  Last Call

about arithmetic operation of feComposite is mentioned:
 
'If the arithmetic operation is chosen, each result pixel is computed using 
the following formula:
result = k1*i1*i2 + k2*i1 + k3*i2 + k4'
 
What is especially i1 and i2?
My assumption is, that it is the value of the corresponding channel of
the input indicated by the attributes in for i1 and in2 for i2?
If this is correct, my suggestion is to add something like:
 
',where i1 and i2 indicate the corresponding pixel channel values of
the input images, indicated by the attributes in for i1 and in2 for i2,
and k1, k2, k3, k4 indicate the values of the attributes with the
same name.'
 
Another suggestion to improve the understanding of the
other operations is to add formulas for the other operations
as well. This can help authors a lot, because the original 
article from Porter and Duff is not trivial to find for all readers, 
for example currently here an online version:
http://keithp.com/~keithp/porterduff/p253-porter.pdf
 
Additional suggestion for the related example:
Add a generic font-family -
Instead of font-family="Verdana" use for example 
font-family="Verdana, sans-serif"

Original mail:
http://www.w3.org/mid/201006291243.33346.Dr.O.Hoffmann@gmx.de
Received on Tuesday, 29 June 2010 13:35:49 UTC

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