[Digikam-devel] [Bug 224999] Thumbnails blury after upgrade to 1.0.0 from 0.10

[Gilles Caulier]

https://bugs.kde.org/show_bug.cgi?id=224999


Gilles Caulier <caulier.gilles at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|general                     |Thumbnails
            Version|unspecified                 |1.0.0




--- Comment #7 from Gilles Caulier <caulier gilles gmail com>  2010-01-31 15:35:44 ---
This problem have been already discuted to digikam-user at kde.org mailing list
recently.

With 1.0 release, thumbnails are stored in a dedicated database using PGF
format (wavelets compression) to reduce space on your hard drive.

With digiKam 0.10, PNG format is used.

It sound like the PGF compression ratio used in digiKam 1.0 is a little bit
high. Perhaps we can just reduce this value by one point or provide a simple
settings in setup dialog.

Code relevant is there :

http://lxr.kde.org/source/extragear/graphics/digikam/libs/threadimageio/thumbnailcreator.cpp#501

'4' is the compression level. A value up to to 4 is very destructive. A lesser
value has better quality, but size data is up. A zero value is a lossless
compression as PNG.

This can be also an issue to libpgf, as an improvement to do to algorithm to
preserve quality of image in all case. I know that pgf team is focused to
provide a fast algorithm against quality when compression level is up

Gilles Caulier

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