A Standard for Thumbnailers
Carsten Haitzler (The Rasterman)
raster at rasterman.com
Thu Jan 11 03:46:04 PST 2007
On Wed, 10 Jan 2007 16:23:17 +0100 Benedikt Meurer <benny at xfce.org> babbled:
> Erlend Davidson wrote:
> >> it makes use of the fact that JPEG's are DCT's
> >> and you get "free" downscaling on decode by factors of 2, 4 and 8
> >> times in each
> >> dimension simply by decoding the DCT at a different output res (and
> >> throwing
> >> out higher frequency DCT elements). it means for an incredibly faster
> >> decode
> >> and thus thumbnail generation is sped up massively. you speed up the
> >> other half
> >> of this work by using JPEG output for thumbnails. it makes a
> >> difference. a
> >> perceptible and measurable one. people notice.
> > Could a similar optimisation be applied to PNG to generate those
> > thumbnails very quickly?
> BTW. both Thunar and Nautilus use the same trick with libjpeg, so that
> won't save time anyway. Saving to JPEG won't boost performance either.
> What's however interesting is the saved disk space.
yes it will boost performance - see my previous mail. i tested ONLY writes to
png or to jpeg. jpeg won - by a huge factor compared to png. that speed test
didnt do the reading bits at all.
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The Rasterman (Carsten Haitzler) raster at rasterman.com
Tokyo, Japan (東京 日本)
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