[Digikam-users] jpeg compression

[Bjørn Kvisli]

Torsdag 28 juni 2007 16:31, skrev Arnd Baecker:
> On Thu, 28 Jun 2007, [iso-8859-1] Bjørn Kvisli wrote:
> > Arnd,
> >
> > I took an image out of the camera ( a Kodak C40, this time) and saved it
> > with different values for jpeg quality. The orginal file was 1.2 MB big,
> > and here are the sizes with diffrerent levels of jpeg quality:
> >
> > 75 -> 1.3 MB
> > 85 -> 1.8 MB
> > 90 -> 1.9 MB
> > 92 -> 2.3 MB
> > 95 -> 2.6 MB
> > 97 -> 3.2 MB
> > 100 -> 4.5 MB
> >
> > All of them bigger than the original file. I don't thimk I understand
> > this.
>
> This suggests, that maybe something like 70 was used inside of the camera?

If I understand this right, assuming that the Kodac C340 uses jpeg quality of 
70 internally, it makes no sense to set a higher value in Digikam?

Hm.. I must find out what kind of compression my Nikon uses.

>
> >From the number of pixels Nx * Ny, the number of bytes needed
>
> to store the image (without) compression should follow from
> Nx * Ny * (8+8+8), i.e. one Byte per R, G, B.
>
> What is the resolution of your camera?
The resolution is 2576x1932 (4.98Mpx)
>
> Anyway, overall the above looks pretty reasonable to me.
>
> Best, Arnd
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