[webkit-qt] Proposal for switching image decoders from Qt to WebCore

simon.hausmann at nokia.com simon.hausmann at nokia.com
Thu Feb 16 23:22:54 PST 2012

Apologies for the top-quote.

I'm not sure that using the WebCore decoders outside of WebKit has many benefits, because performance
wise it seems that they're just as "fast" as the Qt ones but using them outside of WebKit would require an
extra API layer that in turn may have a performance cost. The extra features are nice but maybe not too
difficult to implement either.

Regarding a fallback to Qt Image plugins: I'm perfectly fine with this, although I don't see much use for
supporting web content that nobody else supports (when it comes to images). So I'm not very interested
in doing that part of the work myself, but I'd be more than happy to review patches that implement this.


P.S.: Allan, I just saw that WebCore does have the webp decoder :)

From: webkit-qt-bounces at lists.webkit.org [webkit-qt-bounces at lists.webkit.org] on behalf of ext Allan Sandfeld Jensen [kde at carewolf.com]
Sent: Saturday, February 11, 2012 20:27
To: webkit-qt at lists.webkit.org
Subject: Re: [webkit-qt] Proposal for switching image decoders from Qt to       WebCore

On Friday 10 February 2012, Simon Hausmann wrote:
> Hi,
> I'd like to propose that we switch over to using the WebCore image
> decoders.
> Zoltan has spent some time comparing performance and memory usage between
> the ImageDecoderQt (and the qt plugins for image decoding) and the WebCore
> image decoders, in https://bugs.webkit.org/show_bug.cgi?id=71555
> My interpretation of the result is that performance and memory usage wise
> there's not much of a difference. However the WebCore image decoders have
> some advantages that are of a different nature:
>     1) They are an actively maintained piece of code. Unfortunately the Qt
> image decoder plugins are subject to less tender loving care. The WebCore
> decoders are used by pretty much all other ports, and from my totally
> biased point of view we have also found them working great for the N9 with
> the Qt based browser/webkit.
>     2) They support image downsampling, which is particularly nice for
> mobile devices with less memory than our gigabyte filled workstations.
>     3) The jpeg decoder supports progressive/interlaced jpegs, which is
> again an nice thing for image loading over slow connections.
> Therefore I'd like to re-open https://bugs.webkit.org/show_bug.cgi?id=32410
> .
> Any opinions / objections / thoughts?
If it was possible I would like it to be possible for Qt to handle any images
not supported internally in WebCore.

Also would it be possible to port the webcore image decoders to Qt so other Qt
applications can benifit from faster or more featureful decoders?


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