[Webkit-unassigned] [Bug 29279] [Qt] Use RGB16 format for images on Symbian platform

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=29279





--- Comment #17 from Holger Freyther <zecke at selfish.org>  2009-10-06 07:30:34 PDT ---
(In reply to comment #15)
> (In reply to comment #13)
> > > First, QImage::Format is internal definitions and may change
> > > more frequently than public interface. Second, it has many more formats that we
> > > don't really support. And what we really care is the bit-length of the format
> > > not other details. So I plan to use a new enum that only has rgb16 and rgb32.
> > > Would you let me know what your thought on this? Thanks,
> > 
> > It's a public API, it is not "internal" at all.
> > 
> > Another concern: what about 5-5-5 in some other platforms (not Symbian)?
> 
> The conversion is triggered only if
> 1. no alpha channels
> 2. the original format is RGB32
> 3. new format is RGB16

Ah sorry, I didn't attempt to fully parse the code.


> 
> With the current patch, no code changes the default setting to RGB16. Even
> browser client from other platform starts to use this API, whether internally
> 5-5-5 or 5-6-5 is used is transparent to the client. I should probably change
> the title of this bug to "Using RGB16..." to make it less confusing.

Well the point is that this is a decision that the API user should not take as
he has no idea about the consequences on the platform. On X11 this will kill
performance even more.

Two factors for speed and memory usage: Decode the image to what you want
instead of doing color conversion afterwards (in QImageReader/QImageIO), limit
the maximum size of images (see WebCore decoders).

And there is an easy way to convince me, I have created benchmarks and if less
memory in these benchmarks is allocated and they perform faster I'm open to any
change. So far I think the fix should be in QImageReader.

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