Bug 115158 – Account for CTM scale when deciding the image resampling algorithm.

• Component: Images
• Status: NEW

[Ryosuke Niwa]

We might want to consider merging:

https://chromium.googlesource.com/chromium/blink/+/b772b4d7c24b66bebba703fd2ef89fbe73ea1935

Account for CTM scale when deciding the image resampling algorithm.

ImageQualityController considers the image size and layout size when
computing which resampling algorithm to use, but did not account
for the current transform. This was noticable as 'bouncing' when
scaling an image direclty with a transform.

This patch incorporates the context's CTM (which includes scale
but not zoom) into the resampling calculation. Because the
ImageQualityController runs on a 500ms timer, a manual test
has been added.

[Ahmad Saleem]

Not removed:

https://github.com/WebKit/WebKit/blob/786e7036ff95fecccbd5ec1aae8a39a523227f1e/Source/WebCore/rendering/ImageQualityController.cpp#L125

to Line 127.

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Added these two lines (155 & 156):

https://github.com/WebKit/WebKit/blob/786e7036ff95fecccbd5ec1aae8a39a523227f1e/Source/WebCore/rendering/ImageQualityController.cpp#L155


_____

LayoutSize not detailed and also not updated below:

https://github.com/WebKit/WebKit/blob/786e7036ff95fecccbd5ec1aae8a39a523227f1e/Source/WebCore/rendering/ImageQualityController.cpp#L172

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Above are some examples, which indicates that it might be added in some shape or form but not completely.. Appreciate if someone can confirm. Thanks!

[Ahmad Saleem]

I tried it with following:

https://github.com/WebKit/WebKit/pull/5111

but it seems that this optimisation was removed in follow-up:

https://src.chromium.org/viewvc/blink?revision=194338&view=revision

I am going to close by PR despite review from Said because it is leading to build failures as well. Thanks!