[Webkit-unassigned] [Bug 26749] Canvas: rotation of 'no-repeat' pattern still has small error

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=26749





--- Comment #7 from Shinichiro Hamaji <hamaji at chromium.org>  2009-07-16 04:27:22 PDT ---
Sorry for the poor description/title of this bug. I've attached an HTML which
can describe why I want to use smaller value than before. 1<<23 is the
precision of mantissa of floats and using this means that the error is <1px. I
think 1px error can be still visible.

The HTML I've attached is putting 3x3 image whose shape is '+' vertically. As
it doesn't change the value of X-axis, you should see a vertical straight line
like "After the patch". However, with current WebKit, the line is not straight
like "Before the patch". If we use 1<<22 as this value, the error should be
<0.5px.

As WebKit is doing anti-alias for rotation, the image changes if we use 1<<21
or something smaller value. However, I think no one would be care about such
tiny changes. So, I think 1<<22 would be OK.

I'll update the patch with more description and test case.

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