[webkit-dev] Newbie question re: raw bitmaps

Eric Seidel eric at webkit.org
Wed Dec 22 14:59:21 PST 2010

Platforms provide their own image decoders.  Some of them use the
cross-platform image decoders checked into WebCore:

A quick skim of mozilla's bug on the subject:
leads me to believe there is currently no patent-safe way to use JPEG-XR.

The only platform which has JPEG-XR natively is Windows, however both
Apple's Windows port and Chromium's windows port use the checked-in
image decoders.

I think WebKit is unlikely to support JPEG-XR any time soon.

Without mozilla supporting it (or much content on the web using it)
there is little reason to add support.


On Wed, Dec 22, 2010 at 4:28 PM, Alex Danilo <alex at legrope.com> wrote:
> Hi All,
>        Sorry to post a newbie question.
>        My name's Alex Danilo, I've been doing some SVG stuff over the past
> few years and now have spent the past few months looking into the SVG
> implementation in WebKit.
>        What I'm tyring to do is add a new image format in the engine
> as an exercise.
>        I am trying to add support for JPEG-XR (formerly HD-Photo) as
> a new supported image format for the <image> element (and <img> in
> HTML I guess too).
>        Looking at the ports, code etc. this all plumbs via the Image
> class, BitmapImage class, etc.
>        For some ports, like CG I see that the decode is done lazily
> and defers it to CG so that no intermediate bitmaps are generated.
>        For JPEG-XR, I will have to unpack the ARGB32 bitmap somewhere
> in memory and do a GraphicsContext drawImage() call to paint it to
> the canvas.
>        So my question is, is there any preferred or desirable method
> to accomplish this? i.e. how should I structure the interface to the
> Image class to make sure it works on all ports without creating
> a dog's breakfast of it?
>        All tips and pointers greatly appreciated.
> Cheers,
> Alex
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