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

[Andi Clemens]

Hmm why do we need alpha channel support? Never seen a photo with an alpha 
channel :D

Well anyway I can't say what I prefer, I can only say that with big 
collections (and we must check this, because this might become quickly an 
issue) the thumbsDB is awfully slow.
And I don't think any file format will save us from this, because it is sqlite 
that is not good performing here.

Andi

On Sunday 14 June 2009 20:53:14 Gilles Caulier wrote:
> 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 :
>
> http://en.wikipedia.org/wiki/JPEG_Network_Graphics
>
> Problem : there is no Qt4 support for JNG :
>
> http://doc.trolltech.com/4.5/qimagewriter.html#supportedImageFormats
>
> ...and kimgio do not have a plugin for that...
>
> So for me, PGF is the only alternative...
>
> Gilles
>
> > Marcel
> >
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