- From: Jasper van de Gronde <th.v.d.gronde@hccnet.nl>
- Date: Wed, 10 Nov 2010 11:15:23 +0100
- To: Anthony Grasso <Anthony.Grasso@cisra.canon.com.au>
- CC: "www-svg@w3.org" <www-svg@w3.org>, W3C SVG Public List <public-svg-wg@w3.org>
Hi, I see the divisor as being nothing more or less than a convenient way of scaling the kernel, so not as a separate entity. So in the options I listed I assumed: cF = cO (*) (kernel/divisor) aF = aO (*) (kernel/divisor) With (*) standing for convolution, and cO/aO for the original color and alpha channels. (With the F standing for filtered.) Regards, Jasper On 2010-11-10 02:06, Anthony Grasso wrote: > Hi Jasper, > > I was given ACTION-2900 [1] to investigate the bias attribute. > > As you're aware the specification currently says when preserveAlpha="false" to apply the convolution to all channels. Currently in the specification, the formula to do the convolution for that case is: > > cR = (cF * kernel)/divisor + bias > aR = (aF * kernal)/divisor + bias > > I agree that the definition of 'bias' is not clear at all and should be changed. > > Regarding how it is used in a filter mathematically, your options listed below do not take into account the filter 'divisor' that the current formula does. I would like to know where you think the 'divisor' value fits in with your options that you have specified. > > Cheers, > Anthony > > [1] http://www.w3.org/Graphics/SVG/WG/track/actions/2900 > ... >> <quote> >> For reference, the pseudo-code in the SVG specification suggests the >> following (preserveAlpha=false): >> ------------------------------------- >> Option 1: >> aF = filtered alpha without bias >> cF = filtered (premultiplied) color without bias >> aR = aF + bias >> cR = cF + bias >> ------------------------------------- >> ...
Received on Wednesday, 10 November 2010 10:15:54 UTC