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

Gilles Caulier caulier.gilles at gmail.com
Sun Jun 14 19:53:14 BST 2009

2009/6/14 Marcel Wiesweg <marcel.wiesweg at gmx.de>:
>> 2009/6/13 Marcel Wiesweg <marcel.wiesweg at gmx.de>:
>> >> Result are better than PGF, from speed and space consumption point...
>> >
>> > For me results with JPEG are better as well.
>> For me, as Mik said, JPEG give artifact on thumbs, with 256x256 size,
>> especially with image which have geometric forms (wall, houses,
>> momuments) or high subject contrast as flowers taken in macro mode and
>> with large zone with same colors ( it's not visible with complex
>> images composition with high levels of details) . Sound like
>> anti-aliasing is not visible.
>> I tried 90 compression instead 85, but it still visible.
>> I cannot see this problem with PGF...
> I see this dilemma:
> PGF: quality good, file size good, speed bad            + + -
> JPEG: quality bad, file size good, speed good   - + +
> PNG: quality good, file size bad, speed good    + - +
> (JPEG2000 has the same properties in this listing as PGF but is slower, so I
> left it out)

and JPEG2000 iostream for QImage implemented to kdeimgio do not work...

> It's pretty normal in life that you can't get everything you want, and here it
> seems we need to decide to sacrifice either quality, disk space or speed.

Ah ah... and now i found another point con JPEG : alpha channel :

PGF : ok
PNG : ok
JPEG : no.

Note : JPEG2000 : ok

well, JPEG no not support alpha chanel... If you try to display  a
thumb from an image with alpha, this channel will be replaced by white
(if i'm not too wrong). I remember an old B.K.O entry about a dumy bug
in the past....

We need to support alpha chanel. No way.

To wrap around JPEG, there is a solution : JNG. What's is that ? It's
PNG file container using JPEG compression and alpha support :


Problem : there is no Qt4 support for JNG :


...and kimgio do not have a plugin for that...

So for me, PGF is the only alternative...


> Marcel
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