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

[Gilles Caulier]

2009/6/13 Mikolaj Machowski <mikmach at wp.pl>:
> 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 :(

Marcel, do you see this comment from Mik about JPEG and PGF performance  ?

Gilles