Repro is easy for me on two Win7 machines: 1) Load the linked page. 2) Switch away from the tab. 3) Switch back to the tab with the image. 4) Watch the text carefully. About a second after switching back to the image, it should jump about a pixel upwards for a frame before reverting to its normal state. At a guess, this sounds like something weird with the screenshotting code. The image is resized (shrunk), so maybe it's an interaction with the downsampling code? Most curiously, this seems to stop reproducing if you have the full-size image loaded in a background tab. It starts to reproduce again if you close the background tab with the full-size image. Perhaps an issue with zooming and throwing out decoded image data?

Does flipping image.high_quality_downscaling.enabled fix the problem? It sounds a lot like that is the cause.

(In reply to Timothy Nikkel (:tn) from comment #1) > Does flipping image.high_quality_downscaling.enabled fix the problem? It > sounds a lot like that is the cause. Yep. Setting that pref to false makes the issue disappear, and re-enabling the pref makes it reappear.

Something like bug 832400 probably is about the same issue then.

This would count as a regression?