[Webkit-unassigned] [Bug 41036] REGRESSION (r61341): Image interpolation quality changes during scrolling and when activating / deactivating application

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=41036





--- Comment #3 from Mark Rowe (bdash) <mrowe at apple.com>  2010-06-23 11:18:10 PST ---
The attached page still shows poor performance with your change: all of the images change interpolation quality at once, leading to hangs of between half and one and a half seconds as every image is resampled at once.  Maybe this is better than it was, but it hardly seems like ideal performance.

I have to confess that I don’t really understand what is going on here.  It appears that any time we’re asked to repaint the image we first repaint it using the lower interpolation quality before repainting it at the higher interpolation quality.  This leads to a very visible shift in the image after changing tabs, scrolling, deactivating the window, activating the window, forcing the window to repaint via the Debug menu, etc.  I don’t think that this shifting is acceptable on pages that are clearly not doing anything heavyweight (whether it be resizing images rapidly or having many tens of resized images).  Whatever heuristic is being used to determine when to use the lower-quality interpolation needs to be smarter than just blindly doing it whenever a resized image repaints.

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