[Digikam-devel] extragear/graphics/digikam/digikam

[Mikolaj Machowski]

On Friday 12 June 2009 21:07:26 Gilles Caulier wrote:

> > Used this for my files (15,000):
> >
> > 1) size of database: 243 MB, size of .thumbnails/large: 1.3GB
> > 2) creation time - for me recreation of all thumbnails takes so long that
> > I have to do other things in meantime so it is incomparable (and data
> > useless) but just for interest it was cut 20% - and "live" creation of
> > thumbs (displaying them with empty database) was faster for me than
> > previously 3) what for me is most important - time of display of images
> > which thumbs are already in database: unfortunately there is scientific
> > method, just feelings - maybe bit faster, definitely not slower
> > 4) quality of images (used default PGF, q=4, don't know how to switch to
> > JPG):
>
> To switch to JPG, it's easy :
>
> http://lxr.kde.org/source/extragear/graphics/digikam/libs/threadimageio/thu
>mbnailcreator.cpp#481
>
> Change this line to dbInfo.type = DatabaseThumbnail::JPEG;
>
> recompile, install. Remove your thumbs database file and start digiKam
> again....

OK. First note: no way default JPEG comression for Qt is 85. Compiled only 
with your change and JPEG artefacts were visible in many images. Size of 
database was 142MB. Creation time comparable with PGF version, but quality 
much lower.

Tested again with declaring 85 in 

http://lxr.kde.org/source/extragear/graphics/digikam/libs/threadimageio/thumbnailcreator.cpp#498

And quality was much better with database size of 184MB and again roughly the 
same time of creation and quality similar to PGF version. However JPEG based 
db is much more resources intensive, eg. playing movies wasn't fluent while I 
was able to view them comfortably while creating PGF db. Quality slightly 
lower comparing to PGF but not dramatically. Time of display comparable. Pity 
you cannot change chroma subsampling when making JPEGs directly in Qt :(

m.