Picture viewer?

Carsten Haitzler (The Rasterman) raster at openmoko.org
Tue Feb 12 01:42:11 CET 2008

On Sat, 9 Feb 2008 19:38:29 -0800 (PST) Asheesh Laroia <asheesh at asheesh.org>

> On Sun, 10 Feb 2008, Stroller wrote:
> > On 8 Feb 2008, at 23:42, Clarke Wixon wrote:
> >
> >> Michael 'Mickey' Lauer <mickey at ...> writes:
> >> 
> >>> ipkg install gpe-gallery.
> >> 
> >> . . . which works, but is s-l-o-w when reading 8 megapixel digicam 
> >> pictures, for
> >> example.  Probably with sanely-sized pictures it would be quite a bit 
> >> better.
> >
> > Please excuse me if this is a naive question, but isn't any image viewer 
> > going to be slow, dealing with 8 megapixel pictures, running on a 200mhz 
> > - 400mhz processor?
> Not to mention eight megabytes of I/O from the micro-SD slot.  I don't 
> have my Neo on-hand, but it'd be great to see some performance numbers 
> that can indicate what sort of performance is reasonable to expect.

actually 8mpixel jpegs normally are about 2-4mb for file IO. as for  resizing,
you can actually get resize for free on load with jpeg just by decoding a
subset of the DCT info - the load is actually sped up by a fair margin. this is
easy. so you can resize an 8mpixel image (3246x down to 405x306) AND load it
much faster than only loading the 8mpixel image on its own. :)

> > I'd guess that the GPU's hardware might be used to accelerate image 
> > resizing in GTA02, but ...
> >
> > IMO you might be better off writing a bash script on your main machine 
> > that uses ImageMagick to resize the images, then copy them across.
> Yes - and in fact, JPEG supports embedded thumbnails that should not even 
> require you to read the whole image as I feared is the major time sink 
> (and certainly not require you to actually decode the whole image).

that's possible if the exif data is still there. the above is a generic solution
that works for all jpeg images though. :) as i said - it also is supported by
libjpeg - and is exported and made easy by libraries such as epeg and evas :)
(evas has load options where u can request downscaling of images at load time.
if it is possible to do the loader will do it and with jpeg it comes "for free"
on load - in fact speeds sup the load).

> -- Asheesh.
> -- 
> Start the day with a smile.  After that you can be your nasty old self again.

Carsten Haitzler (The Rasterman) <raster at openmoko.org>

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