[Digikam-users] jpeg compression

Thorsten Schnebeck thorsten.schnebeck at gmx.net
Sat Jun 30 17:23:04 BST 2007

Am Freitag 29 Juni 2007 schrieb Hugo Palma:
> This discussion has really helped me understand some more things about file
> formats.
> So if i'm only taking into the account picture quality and flexibility and
> don't care about metadata tiff is better than png for editing right ?
No :-)

TIFF is a very flexible but also complicate container for image data. This 
flexibility is the reason that many raw formats are based on TIFF internal 
directory structures but this leads also to the problem that a library like 
libtiff can not cope with every special vendor solution.

PNG is simple and has everything you need for storing an image.

To keep it simple in PNG you can e.g. not handle CYMK (print) or real number 
based (HDR) image data nor handle multiple images in one file.

But being simple PNG often has better compression ratio than standard TIFF.

To make it short: Only looking at lossless storing images to a file TIFF and 
PNG are equal. But digiKam has better PNG support compared to TIFF as the 
used PNG libraries are simply better than the free and open tiff libs.

So, for long time storage today PNG is the way to go as it preserves the 
metadata if the image.

This may change in the future when TIFF-based DNG-format gets better 
support. ;-)



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