Comment 46 for bug 248271

(In reply to comment #37)
> In the originals subframes are encoded with dispose_op=background and
> blend_op=over, despite being full frames 16x16. No need to waste CPU time
> clearing the background, and then doing proper blending.

I don't think that should make any difference. AFAIK we decode after loading into a series of 24bit RGBA surfaces, and just flip between them. So, how the image was encoded should have no effect. The APNG dispose/blend flags should only be used in the initial decode, not as the the animation plays.

> My throbbers use dispose_op=none and blend_op=source, they are in grayscale,
> less pixels are half-transparent, more pixels are fully opaque or fully
> transparent.

I'm not sure grayscale should matter either, as I'm pretty sure it will still get decoded to RGBA surfaces (joe?). I'd assume blending fully opaque/transparent pixels would be faster, but we're still only talking about a handful of pixels per frame...