[Webkit-unassigned] [Bug 49365] [chromium] Add canvas.toDataURL("image/jpeg", quality) support

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=49365





--- Comment #8 from Stephen White <senorblanco at chromium.org>  2010-11-25 07:25:17 PST ---
(From update of attachment 74360)
Thanks for taking this on!

View in context: https://bugs.webkit.org/attachment.cgi?id=74360&action=review

> WebCore/ChangeLog:16
> +        alpha channel when extracting an "image/jpeg".toDataURL().  The correct answer
> +        needs more investigation.

I don't know if it helps for this particular test, but some of the canvas/philip tests require a different unpremultiply that the one implemented in SkUnPreMultiply, in order to achieve roundtrip lossless conversion on a certain set of colours.  See http://trac.webkit.org/changeset/71760, function mulDiv255Ceil() in ImageBufferSkia.cpp.  The test was canvas/philip/tests/2d.imageData.put.unchanged.html.  If this does fix the problem, it would be ideal if you could upstream this function to Skia.

> WebCore/platform/image-encoders/skia/JPGImageEncoder.cpp:107
> +            SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(*pixel++);

See above:  check if mulDiv255Ceil() fixes the JPEG+alpha case.

> WebCore/platform/image-encoders/skia/JPGImageEncoder.cpp:117
> +        out->m_buffer.resize(8192);

This magic value should be in a constant.

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