[Webkit-unassigned] [Bug 22150] New: Color.cpp gives wrong colors for a alpha < 1

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=22150

           Summary: Color.cpp gives wrong colors for a alpha < 1
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: vbs85 at gmx.de


Color.cpp gives wrong colors, for an alpha lower than 1. This is a problem for
canvas in Qt and Cairo. Cg seems _not_ to be affected.
It's difficult to messure it or make a real LayoutTest for it, since Qt and
Cairo lacks a fully working getImageData support. But it is difficult to
implement getImageData as long as we can't test it because of wrong colors.

I'll upload a simple test. If you make a screenshot and compare the color
values (rgb) with the color-values of ff or opera, you can see that they
differs from ff and opera. ff and opera give the right values.

I checked if it is a problem with canvas. But canvas has the right colors. The
colors in canvas are parsed by CSSParser::parseColor and are given to the
GraphicsContext by CanvasStyle.cpp. But the GraphicsContext gets the wrong
colors.
I can't say if it is a problem of Color.cpp or CSSParser.cpp.

See also: https://bugs.webkit.org/show_bug.cgi?id=21575#c5

And again: Cg seems not to be affected.


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