967278 - Support downscaling at the same time as decoding in PNG/JPEG

Status: RESOLVED WORKSFORME

(Core :: Graphics: ImageLib, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

WebKit added support for something like this in https://bugs.webkit.org/show_bug.cgi?id=28308

The approach they use is to have a table that maps from destination buffer locations to source rows. This isn't great because it only gives NEAREST filtering and the extra table lookup doesn't help for speed.

We should instead come up with an approach that does a proper bilinear scale.

Comment 1

[Milan Sreckovic [:milan] (needinfo for best results)]

Is this the approach we should use to deal with bug 854795?  Should we first do what WebKit does, then improve it?

Comment 2

[Jeff Muizelaar [:jrmuizel]]

(In reply to Milan Sreckovic [:milan] from comment #1)
> Is this the approach we should use to deal with bug 854795?  Should we first
> do what WebKit does, then improve it?

Yes, this is the backend step to bug 854795. I don't think what WebKit does is shippable. From what I can tell it was only ever used by Torchmobile presumably in the Blackberry browser. They recently removed this code from Blink.

Comment 3

[Timothy Nikkel (:tnikkel)]

We did this elsewhere.