[Webkit-unassigned] [Bug 139414] New: Small rounding error in SVG color transformation

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Mon Dec 8 14:51:38 PST 2014


            Bug ID: 139414
           Summary: Small rounding error in SVG color transformation
    Classification: Unclassified
           Product: WebKit
           Version: 528+ (Nightly build)
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: SVG
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: sabouhallawa at apple.com
                CC: zimmermann at kde.org

Created attachment 242848
  --> https://bugs.webkit.org/attachment.cgi?id=242848&action=review
Test case

Open the attached test case and compare it with the expected file.

Result: With naked eyes, the two will look very similar. But if a comparison tool is used, the result will be they are different.
Expected: The test case and the expected file should exactly the same.

The test case has the following filter effect:
    <feColorMatrix type="matrix" values="0 1 0 0 0   0 0 1 0 0   1 0 0 0 0   0 0 0 0.5 0" ...>
This filter effect is applied to the following target element:
    <rect x="0" y="0" width="100" height="100" fill="#123456" filter="url(#f1)"/>
The resulting color should be equal to: r=0x34, g=0x56, b=0x12 and alpha=0.5

The expected file has only the following element:
    <rect x="10" y="10" width="80" height="80" fill="#345612" fill-opacity="0.5"/>

With closer look at the test case, one can see a difference of 1/256 in every color component when it is compared with the expected file.

NOTE: We may end up not fixing this bug. But we need to investigate to understand where the rounding happens. And based on this investigation we will decided if it is worthy fixing or not.
NOTE: The attached test case is imported from Mozilla SVG test suite.

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