Thanks. I didn't mean to suggest something like this should be part of
WebKit. I was wondering if anybody had any experience they could share
that might help me or others come to faster conclusions about the
usefulness or feasibility of this in custom ports. If I implement the
formats below I can report back on my results and possibly donate to
ports that might be interested in this, such as OWB.
Thanks.
Paul
On Dec 14, 2008, at 1:12 AM, Paul Pedriana wrote:
For a lot of web pages, images are the primary source of memory
usage. These images seem to be typically stored as RGB or ARGB data
in the BitmapImage class.
This isn't always true though. For example, the ports that use CG
have CGImageRefs and not raw ARGB data.
It seems to me that applications that wish or need to save runtime
memory could benefit from runtime image compression whereby images
are stored in some compressed form instead of RGB or ARGB formats. I
am currently looking into this possibility and I'm wondering if
anybody has previously looked into it.
My current idea is to support two kinds of compressed images: RLE and
YCoCg-DXT5. The former could be for any images that are simple
enough, and the latter could be for general images and give a fixed
4:1 compression ratio. RGB transforms to YCoCg with better
decorrelation (breakdown of RGB to YCC) than YCbCr and many images
can get PSNR values over 40 (i.e. hard to tell from original). If the
computer has decent vector processing or a programmable GPU, the
performance could be decent, otherwise it depends on the CPU. (A)RGB
could of course remain as a fallback.
I'm wondering if anybody has looked into runtime image compression
with WebKit and considered options such as this.
This could in theory be done as a separate library that is then just
used by the specific ports of WebKit that might need it. I'm not
convinced it would need to be part of WebKit itself.
dave
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