[Bug 224999] New: Thumbnails blury after upgrade to 1.0.0 from 0.10

[Vlado Plaga]

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


Vlado Plaga <[hidden email]> changed:

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--- Comment #20 from Vlado Plaga <rechner vlado-do de>  2010-02-13 10:41:57 ---
I'm glad the source of this problem seems already found!
If given the choice (like in gqview or geeqie) I always opt for high quality
resizing of thumbnail pictures - even though I'm already on a "slow" machine (1
GHz). Maybe digiKam could also offer an option, or just change to a higher
quality default re-size algorithm.

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[Marcel Wiesweg]

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





--- Comment #21 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-02-13 14:38:44 ---
My suggestion would be to disable the cheat scaling for now and use good old
smooth scaling? Gilles?

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[Gilles Caulier-4]

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





--- Comment #22 from Gilles Caulier <caulier gilles gmail com>  2010-02-13 14:41:55 ---
yes Marcel, fine for me...

Gilles

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[Marcel Wiesweg]

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


Marcel Wiesweg <[hidden email]> changed:

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             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |FIXED




--- Comment #23 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-02-13 16:38:35 ---
SVN commit 1089637 by mwiesweg:

Disable cheat scaling for thumbnails because of demonstrated quality
regressions.

BUG: 224999

 M  +2 -1      NEWS  
 M  +3 -0      libs/threadimageio/thumbnailcreator.cpp  


WebSVN link: http://websvn.kde.org/?view=rev&revision=1089637

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[Vlado Plaga]

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





--- Comment #24 from Vlado Plaga <rechner vlado-do de>  2010-03-31 10:51:26 ---
What disappointment! I had been looking forward to digiKam 1.2 because of this
fix, but now my thumbnails seem even blurrier than before. I'll attach a
picture with a comparison between digiKam 0.9, digiKam 1.0, and digiKam 1.2.
Could it be that current digiKam only generates very small thumbnails and
upscales them to a width of 256 pixels, if a user wants to see large thumbnail
pictures?

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[Vlado Plaga]

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





--- Comment #25 from Vlado Plaga <rechner vlado-do de>  2010-03-31 10:53:25 ---
Created an attachment (id=42397)
 --> (http://bugs.kde.org/attachment.cgi?id=42397)
Screenshots of three different digiKam versions.

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[Gilles Caulier-4]

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





--- Comment #26 from Gilles Caulier <caulier gilles gmail com>  2010-03-31 10:54:01 ---
Not reproducible there. Please regenerate all thumbnails for your collection
using right option in Tool menu entry.

Gilles Caulier

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[Vlado Plaga]

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





--- Comment #27 from Vlado Plaga <rechner vlado-do de>  2010-03-31 12:14:41 ---
Hm, maybe I made a mistake somewhere, sorry! I tried digiKam 1.2 from Kaelo's
PPA on my notebook, and thumbnails there look good.

I'm currently recompiling digiKam 1.2 on my PPC computer, where I took the
digiKam 1.2 screenshot. I'll write another comment, if there's still a problem
on this computer (the old iMac).

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[Vlado Plaga]

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





--- Comment #28 from Vlado Plaga <rechner vlado-do de>  2010-04-01 18:04:43 ---
After a lot of testing I'm still not sure where exactly the problem comes from,
but it seems like there are both PPC specific as well as Ubuntu (or KDE 4.4)
specific causes involved. I remember the thumbnails' new PGF format had issues
with PPC hardware (big-endian) before, as was discovered in bug #210580.

My findings (from just looking at the surface):

- digiKam 1.2 on Ubuntu 10.04/ AMD64 (KDE 4.4.2) works very well. I tried both
the PPA version and a package compiled from the sources on my system.
Thumbnails look sharp, no matter whether they are displayed at 256 pixels or
slightly smaller.

- digiKam 1.2 on Ubuntu 10.04/ PPC (software versions should be identical to
the AMD64 version) automatically creates very blurry thumbnails, as can be seen
in my attachment from yesterday. But thumbnails look good when I set the slide
to 256 pixels and regenerate the thumbnails using the entry from the "extras"
menu! Still the thumbnails look blurry again when I reduce their size by just a
few pixels, or when I restart digiKam. After a restart, they remain blurry even
in 256 pixel size.

- digiKam 1.2 on Debian/ PPC (sid, with KDE 4.3.4) behaves differently again.
The thumbnails it generates are sharp, as long as they are displayed in 256
pixels width. If I slightly reduce their size, they look very blurry again.
Thumbnails generated under Debian can always be restored to look sharp by
changing their size to 256 - but thumbnails generated under Ubuntu always
remain blurry (also under Debian, where I used the same home account with just
a few pictures).

I'd like to see what is really stored in the "thumbnails-digikam.db", but I
don't know how to do that. My attempt with the "sqlite" command failed.

Should I open a new bug report for this issue? I could call it "Thumbnails
blurry on PPC (big-endian) platform".

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[Marcel Wiesweg]

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--- Comment #29 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-04-01 20:39:51 ---
You need the "sqlite3" tool. Type ".schema" to get the schema. The thumbnails
are stored in PGF format as BLOB.

In the db thumbnails are stored as 256px. That means at initial (slow)
creation, the full image is loaded and then scaled to 256. The original bug
here affected this step.
When loading from the db (fast), the thumbnail is scaled to the desired size
and then converted to pixmap.

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[Vlado Plaga]

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--- Comment #30 from Vlado Plaga <rechner vlado-do de>  2010-04-02 19:17:31 ---
Marcel, thank you for the hint with sqlite3, and for the explanation of the way
digiKam handles its thumbnails.

Indeed I can open "thumbnails-digikam.db" with sqlite3, but I don't know how to
extract a thumbnail from it. Anyway that seems not very helpful to me know -
what would it show, if the thumbnail was already saved blurry under Ubuntu?
DigiKam 1.2 under Debian seems to save good thumbnails anyway, but still
renders them in a blurry way as soon as I change their size.

So I opened a new bug - #233094 - for this new problem.

I currently don't have enough time to learn more C programming, examine how
digiKam works internally, and start searching for the error myself, but I'm
willing to provide more information, or test patches.

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[Gilles Caulier-4]

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

Gilles Caulier <[hidden email]> changed:

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   Version Fixed In|                            |1.2.0

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