[webkit-dev] image downscaling during decoding

[Ilyes Gouta]

Hi,

On Mon, Aug 13, 2012 at 3:46 PM, Anton Obzhirov <a.obzhirov at samsung.com> wrote:
> Libjpeg has some internal support for downscaling already (2x, 4x). Not sure
> about
>
> Libpng and other libraries.  In general probably it can be implemented  by
> downscaling decoded row of the pixels on the fly using callback API
> provided.

If such a callback API for row-based resizing comes to fruition, then
let's (also) not rule out whole-picture h/w accelerated resizing -
such as by making that new API a mandatory stage in the decoding
process.

-Ilyes

>
> From: tomhudson at google.com [mailto:tomhudson at google.com] On Behalf Of Tom
> Hudson
> Sent: 13 August 2012 15:00
> To: webkit-dev at lists.webkit.org; Anton Obzhirov
> Subject: Fwd: [webkit-dev] image downscaling during decoding
>
>
>
> On Mon, Aug 13, 2012 at 9:39 AM, Anton Obzhirov <a.obzhirov at samsung.com>
> wrote:
>
>
>
> We are looking for ways to improve page loading speed and reduce memory
> usage for WebKit in general and for GTK port of WebKit in particular.
>
> One of the ideas is to implement downscaling of the images during decoding
> for image elements with rectangle less then original image size.
>
> At the moment such images are full decoded to a full size buffer and get
> downscaled during rendering.
>
> It can be quite beneficial in term of memory usage and should speed up
> rendering of the pages like image galleries for example.
>
> So what are your thoughts about it?
>
>
>
> Interesting idea! I know Chrome sees memory pressure from the downsampling
> two-step on some pages, so I'd think this is could be useful for us, too.
>
>
>
> Isn't it going to require fairly large and intrusive changes to several
> different third-party libraries, though?
>
> Also, different ports use different image downscaling algorithms; I can
> think of ways to try to enable incremental downscaling callbacks so you
> don't have to implement N downscales in each of M decoders, but none that
> are both general and performant.
>
>
>
> I'd love to see a proposal on this.
>
>
>
> Tom
>
> (from the right account this time)
>
>
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