Comment 80 for bug 263661

FWIW, attachment 351955 shows the background instead of black when using operator-over instead of overriding with operator-source here:

http://hg.mozilla.org/mozilla-central/annotate/0df95f3a6de6/modules/libpr0n/src/imgFrame.cpp#l631

That may often be a little better though still not right, and there are other reasons to use extend-pad.

I'm curious whether the bug here is in calculating scale factors and clips or in the nearest neighbour implementation. However, extend-pad is probably the appropriate solution anyway.