[Digikam-users] questions about the raw importer

[Gilles Caulier]

2008/9/3 Gilles Caulier <caulier.gilles at gmail.com>

>
>
> 2008/9/3 Gandalf Lechner <gandalf.lechner at univie.ac.at>
>
>> Hi Gilles and thanks for the fast answers.
>>
>> Regarding png vs jpg:
>>
>> > I don't recommend to use JPG in your workflow. Use PNG instead.
>>
>> Yes I would like to use a lossless file format, but with png I have the
>> problem
>> that it can produce really big files. For example, I have a raw (cr2) file
>> 9.7
>> MB big, but the png version I got from the digikam converter is 42MB! In
>> comparison to 1.1 MB for the jpg that's just way too big; in particular
>> since
>> it's much larger than the raw itself.
>>
>
> PNG (or TIFF) file size against RAW file size are relevant of 2 points:
>
> - 1/ image data are in RGB color space and take more place.
> - 2/ image data are lossless compressed (deflate compression for PNG and
> TIFF)
>
> Both file format don't know wavelet compression yet.
>
> Alternative to PNG or TIFF :
>
> - JPEG2000 : wavelet/lossless compression and support all metadata (need
> future Exiv2 0.18 for that). File size are reduced (x1/2 - 1/4 against PNG).
> Big problem : it very slow to compress/uncompress
>
> - DNG : use lossless JPEG compression with 16 bits color depth (not wavelet
> based). file size reduced (x1/2) but DNG SDK is patented, do not support
> Linux as well, and documentation is dumy for developpers. Licence is not
> opensource but you can use as well with many restriction.
>
> - HDPhoto : wavelet based. file size reduced (as JPEG 2000). But it's M$
> stuff patented and do not support Linux as well, and licence is anti open
> source.
>
> I recommend to read my blog entry for details :
>
> http://www.digikam.org/drupal/node/368
>
>
I forget to said that a possible opensource alternative will be OpenEXR
which use a loosless compression based on wavelet. The problem is metadata
support. I currently investiguate this point to support this foramt in
digiKam as new photo container.

Gilles
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