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[Bug 6327] New: filters-comptran-01-b reference PNG incorrect

From: <bugzilla@wiggum.w3.org>
Date: Sat, 20 Dec 2008 16:46:42 +0000
To: www-svg@w3.org
Message-ID: <bug-6327-2017@http.www.w3.org/Bugs/Public/>

http://www.w3.org/Bugs/Public/show_bug.cgi?id=6327

           Summary: filters-comptran-01-b reference PNG incorrect
           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


Attached is a file which demonstrates how the first three gradients should
render (if I read the SVG standard correctly) by simply substituting the
filtered gradients by gradients which mimic the filtering. I have no idea in
what way, exactly, the current reference PNG is wrong, but it most definitely
seems to be very wrong:
 - The first third of the "table" gradient should be a transition from yellow
to black, without any green. This can be easily verified by considering that in
the original gradient went from #ff0000 to #00ff00 and that the two transfer
functions are mirror versions of each other.
 - At the far left of the "linear" gradient the red channel in the reference
PNG reaches values above 200, while 255*(.5+.25)=191.25.
 - At x=133, the original gradient (at the top) has green value 207, the
"gamma" gradient should therefore have value 255*(2*(207/255)^3+0)=272.8... (so
255, as the values are clamped). In contrast, the reference PNG has value 185.


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Received on Saturday, 20 December 2008 16:46:52 GMT

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