- From: Anthony Grasso <Anthony.Grasso@cisra.canon.com.au>
- Date: Sun, 27 Feb 2011 22:03:10 +0000
- To: W3C SVG WG Public List <public-svg-wg@w3.org>
Hi SVG WG, This is Jaspers response regarding ISSUE-2335. Cheers, Anthony -----Original Message----- From: Jasper van de Gronde [mailto:th.v.d.gronde@hccnet.nl] Sent: Tuesday, 21 December 2010 6:06 PM To: Anthony Grasso Subject: Re: ISSUE-2335: Clarify feConvolveMatrix bias property [SVG 1.1 F2 Last Call] Hi Anthony (/SVG WG), I believe with these latest changes the bias property indeed makes a lot more sense, thank you! Kind regards, Jasper van de Gronde On 2010-12-10 05:57, Anthony Grasso wrote: > Hi Jasper, > > Thank you for help regarding the feConvolveMatrix 'bias' property. > > I was given the task of resolving this issue. The SVG Working Group decided that the bias should be defined as you suggested Option 2. To address this problem, the following changes have been made to the feConvolveMatrix section [1] of the specification: > - Made a correction to the convolution matrix formula [2] > - Added wording to the 'bias' attribute [3] > - Clarified how the 'preserveAlpha' attribute effects the > convolution matrix formula [4] > > Please advise the SVG Working Group if these changes have satisfactorily address the issue you have raised. > > Kind Regards, > > Anthony Grasso > > > [1] > http://dev.w3.org/SVG/profiles/1.1F2/master/filters.html#feConvolveMat > rixElement [2] > http://dev.w3.org/SVG/profiles/1.1F2/master/filters.html#feConvolveMat > rixElementFormula [3] > http://dev.w3.org/SVG/profiles/1.1F2/master/filters.html#feConvolveMat > rixElementBiasAttribute [4] > http://dev.w3.org/SVG/profiles/1.1F2/master/filters.html#feConvolveMat > rixElementPreserveAlphaAttribute > > >> -----Original Message----- >> From: public-svg-wg-request@w3.org [mailto:public-svg-wg- >> request@w3.org] On Behalf Of SVG Working Group Issue Tracker >> Sent: Wednesday, 23 June 2010 6:14 PM >> To: public-svg-wg@w3.org >> Subject: ISSUE-2335: Clarify feConvolveMatrix bias property [SVG 1.1 >> F2 Last Call] >> >> >> ISSUE-2335: Clarify feConvolveMatrix bias property [SVG 1.1 F2 Last >> Call] >> >> http://www.w3.org/Graphics/SVG/WG/track/issues/2335 >> >> Raised by: Erik Dahlström >> On product: SVG 1.1 F2 Last Call >> >> I would really like the bias property clarified in SVG 1.1 SE. The >> problem with the current explanation is that it seems to be >> contradictory (and if you take the most explicit explanation, frankly >> not that useful). >> >> In the explanation of the property it is said to be intended to have >> (as one possibility) a gray zero response. However, in the basic >> convolution formula the bias is added directly to the premultiplied >> color values. If you follow this definition the bias property does >> not give you any effective control over the zero response! Depending >> on the alpha component a bias of 0.5 could be anything from >> out-of-range white to 0.5 gray. >> >> We've discussed this problem before and the last post in that thread >> that I could find was by me (on Nabble, as my laptop, with a lot of >> my e-mails is being serviced) and summarized the progress as follows: >> >> <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 >> ------------------------------------- >> >> I previously suggested: >> ------------------------------------- >> Option 2: >> cR = cF + bias*aR >> ------------------------------------- >> >> You seem to suggest: >> ------------------------------------- >> Option 3: >> cR = cF + bias*(aR-bias) >> ------------------------------------- >> I'm not sure what the advantage of this would be though. For example, >> if you have a uniformly colored shape (opacity also uniform) and >> apply the filter -1 1 (with bias=0.5) I would expect a response of >> (0.25,0.25,0.25,0.5), and not (0,0,0,0.5). >> >> Another option would be to do an explicit conversion from and to >> premultiplied colors: >> ------------------------------------- >> Option 4: >> cR = (cF/aF + bias)*aR >> ------------------------------------- >> Conceptually this might be cleaner, but it does have the disadvantage >> of needing a division. Specifically, what color should result if aF=0? >> </quote> >> >> Original mail: >> http://www.w3.org/mid/4C21BDBC.3090800@hccnet.nl >> >> The information contained in this email message and any attachments may be confidential and may also be the subject to legal professional privilege. If you are not the intended recipient, any use, interference with, disclosure or copying of this material is unauthorised and prohibited. If you have received this email in error, please immediately advise the sender by return email and delete the information from your system.
Received on Sunday, 27 February 2011 22:04:07 UTC