W3C home > Mailing lists > Public > www-svg@w3.org > December 2008

[Bug 6261] New: filters-gauss-01-b incorrectly handles region where rectangles overlap (or does it?)

From: <bugzilla@wiggum.w3.org>
Date: Tue, 02 Dec 2008 14:43:10 +0000
To: www-svg@w3.org
Message-ID: <bug-6261-2017@http.www.w3.org/Bugs/Public/>


           Summary: filters-gauss-01-b incorrectly handles region where
                    rectangles overlap (or does it?)
           Product: SVG
           Version: All Specifications
          Platform: PC
        OS/Version: Windows NT
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Filter Effects
        AssignedTo: schepers@w3.org
        ReportedBy: th.v.d.gronde@hccnet.nl
         QAContact: www-svg@w3.org

Created an attachment (id=606)
 --> (http://www.w3.org/Bugs/Public/attachment.cgi?id=606)
Spreadsheet showing the problem

Currently Inkscape's rendering of filters-gauss-01-b.svg is different from the
reference PNG. However, this is only true for the regions where two rectangles
overlap. This is most apparent with the blurxy test. The top and bottom parts
match almost perfectly while the middle part is clearly different.

I have attached a spreadsheet that shows some graphs demonstrating the problem.
(For the reference PNG only the green channel is shown to reduce unnecessary
clutter.) The graphs correspond to lines extracted at y=220, y=270 and y=320
(from top to bottom). Legend:
  - the continuous green line is Inkscape's output
  - the dashed green line is the W3C reference PNG
  - the brown line is the result of blurring a 45 pixels wide strectch of
    "red" roughly corresponding to the visible part of the red rectangle
    (only the green channel, so all 255 except for the "red" part, which
    is 0)
  - the orange line is the result from alpha compositing the green
    channels from y=220 and y=320 (corresponding to only red and only
As can be seen from the middle graph Inkscape's output matches quite well to
the data computed in the spreadsheet, while the reference PNG's line differs
quite a bit. The orange line was included to rule out the possibility that the
difference was caused by filtering the rectangles separately vs. filtering the
combination, apparently it doesn't matter much which approach is used (for this

So, which image is correct? (And what causes this mismatch?)

Configure bugmail: http://www.w3.org/Bugs/Public/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are the QA contact for the bug.
Received on Tuesday, 2 December 2008 14:43:22 UTC

This archive was generated by hypermail 2.4.0 : Friday, 17 January 2020 22:54:21 UTC