Re: resolution

On Monday 09 September 2002 11:39, poeml_at_cmdline.net wrote:
> On Sun, Sep 08, 2002 at 01:10:38PM +0100, poml_at_poeml.de wrote:
> > Hi,
> >
> > see, the camera has three resolutions: 512 (low), 1024 (med),
> > 1280 (high).
> > The CCD chip is 1024.
> >
> > So, I'm trying to figure out, how under Windoof they interpolate the
> > picture to 1280.
>
> So do you think it is the Winblows that interpolates, not the camera?

Yes, the camera sends 1024x768 both in medium and high resolution mode. Any 
upscaling is done by the Agfa software. It is not simply changing the X and Y 
resolution values inside the JPEG header, the software has to decode the 
JPEG, scale up, and encode back to JPEG.

The camera does not do anything special, the ONLY thing is that when creating 
a medium quality shot, it uses a higher compression ratio. That is ALL! :)

> > So where's the difference? Is it just the JPEG compression factor maybe?
>
> Sounds resonable, since a compression with less loss would allow the
> interpolation...

That's 100% true :-)

A 1024x768 at 150kb can be of much better quality than a 1024x768 picture at 
75kb. But they are still both 1024x768.

Agfa probably scales the image to pretend it is really higher *resolution*, 
and it IS higher quality, but not higher resolution. Probably most users will 
think 1280x960 with a 100:1 compression ratio is much better than 1024x768 at 
20:1 :-))

In our case, we are making a Linux driver. The user knows best! We give the 
user the exact JPEG data the camera gave us. Any modifications the user wants 
to make, scale up, adjust brightness, etc, he can do in his favourite 
program.

If the Agfa software tries to be smart and "fixes" a picture which doesn't 
need to be fixed, too bad! You are out of luck! And if you have a program 
which can do a MUCH better upscale to 1280x960, also too bad, the Agfa 
software already did it for you using the inferior algorithm.

Sounds ok? :-)
Dennis