[Digikam-users] image conversion: size questions

[Michael Eschweiler]

Am Wednesday 17 June 2009 15:15:25 schrieb stefano adami:
> I tried to export a series of raw images to jpg. Raw are 3906x2602, 9MB.
>
> First strange thing is that Jpeg size are around 9MB (like raw) with a
> compression quality set to 75.
>
> So I tried to reconvert image (jpg->jpg) with quality set to 80 and now
> images are around 1,8MB (a correct and appropriate size in my opinion),
> but digikam displays a 16KB size and had apparently lost all images info
> (this sounds like a bug).
>
> It's normal that a 75 quality jpg is bigger than a 80quality jpg?

If you convert a jpg to another jpg with 80% that means 80% from your first 
jpg, it doesn't mean that this enhances the quality of a previous compression 
of 75%. In other words: if your first jpg was compressed to 75% and then you 
do another conversion to 80% what you get is an overall compression to about 
60% in comparison with the 100% of your original image (including the 
corresponding losses...).
Regards,
Michael

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