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

[Anders Stedtlund]

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

           Summary: Thumbnails blury after upgrade to 1.0.0 from 0.10
           Product: digikam
           Version: unspecified
          Platform: openSUSE RPMs
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: NOR
         Component: general
        AssignedTo: [hidden email]
        ReportedBy: [hidden email]


Version:            (using KDE 4.3.4)
OS:                Linux
Installed from:    openSUSE RPMs

Hi

After upgrading digiKam from 0.10 to 1.0.0 most thumbnails seems to be quite
blury. Especially thumbnails for jpeg images. RAW, Canon, seems not to be
effected.

I have tried with regeneration of all thumbnails, but without any luck.

I'm running openSUSE 11.2 with digiKam from KDE:Backports.

I had a little discussion about this on the digikam-users mailing list. A
suggestion was to contact libpgf also. I haven't done that yet, but I will.

/Anders

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[Johannes Wienke-3]

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--- Comment #1 from Johannes Wienke <languitar semipol de>  2010-01-31 14:12:45 ---
Can you please provide a screenshot and, if possible, a screenshot of how this
was before the update?

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--- Comment #2 from  <falolaf gmail com>  2010-01-31 14:25:17 ---
I will try to have a after/before screenshot. I haven't 0.10 installed anymore.

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--- Comment #3 from  <falolaf gmail com>  2010-01-31 14:31:49 ---
Where were the thumbnails stored in 0.10?

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--- Comment #4 from Johannes Wienke <languitar semipol de>  2010-01-31 14:41:29 ---
0.10 used the .thumbnails folder in your home directory.

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[Anders Stedtlund]

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--- Comment #5 from  <falolaf gmail com>  2010-01-31 15:20:23 ---
Created an attachment (id=40413)
 --> (http://bugs.kde.org/attachment.cgi?id=40413)
Thumbnail1, digiKam 0.10

The first thumbnail from digiKam 0.10.

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--- Comment #6 from  <falolaf gmail com>  2010-01-31 15:23:00 ---
Created an attachment (id=40414)
 --> (http://bugs.kde.org/attachment.cgi?id=40414)
Thumbnail1, digiKam 1.0.0

The first thumbnail, for digiKam 1.0.0.

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[Gilles Caulier-4]

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Gilles Caulier <[hidden email]> 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 [hidden email] 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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--- Comment #8 from  <falolaf gmail com>  2010-01-31 15:43:57 ---
Hi Gilles

It was me who opened that discussion :)

Can't we have the user decide what choose the compression level instead of a
fixed value in the code?

Another thing is that the thumbnails are better for raw images or png. How can
that be.

I have uploaded two thumbnails of the same image. The thumbnail from digiKam
1.0.0 is a screenshot, while for digiKam 0.10 I took it from the
.thumbnails/large folder.

/Anders

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[Marcel Wiesweg]

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Marcel Wiesweg <[hidden email]> changed:

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--- Comment #9 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-01-31 21:25:00 ---
Can you also give us the original image?

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--- Comment #10 from  <falolaf gmail com>  2010-02-01 09:26:42 ---
(In reply to comment #9)
> Can you also give us the original image?

I can do that, but I have to wait until I get home.

/Anders

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--- Comment #11 from  <falolaf gmail com>  2010-02-01 11:27:59 ---
I wasn't allowed to upload the image. It's to big. Any suggestions where I can
store it?

/Anders

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--- Comment #12 from Gilles Caulier <caulier gilles gmail com>  2010-02-01 11:33:11 ---
Give an url to web space or send image by mail to Marcel

Gilles Caulier

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--- Comment #13 from  <falolaf gmail com>  2010-02-01 13:13:47 ---
Here's a link to the image:
http://s746.photobucket.com/albums/xx106/falolaf/?action=view&current=gotland_2008-04-27_161621.jpg

/Anders

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--- Comment #14 from  <falolaf gmail com>  2010-02-01 13:19:41 ---
(In reply to comment #13)
> Here's a link to the image:
> http://s746.photobucket.com/albums/xx106/falolaf/?action=view&current=gotland_2008-04-27_161621.jpg
>
> /Anders

That was a bad choice, the image was resized. I will send it by mail instead.

/Anders

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--- Comment #15 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-02-06 14:53:44 ---
Created an attachment (id=40569)
 --> (http://bugs.kde.org/attachment.cgi?id=40569)
Result of thumb extraction and scaling

This image is extracted from the thumbnail generation process and directly
stored as PNG, before PGF compression. Compared to the 1.0.0 thumbnail which
you provide I see some minor blurring on the white wall on the left and in the
white grid in the background, but the major artifacts and the handrail are
already present before libpgf compression

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--- Comment #16 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-02-06 14:57:13 ---
Created an attachment (id=40570)
 --> (http://bugs.kde.org/attachment.cgi?id=40570)
Result of thumb extraction and full smooth scaling

The is also extracted from thumbnail generation process before PGF compression.
This time, I disabled the "cheat scaling" and only used smooth scaling. From my
impression, this is identical to the 0.10 thumbnail and better than the 1.0
version.

This clearly shows that libpgf is not the problem here but the introduction
"cheat scaling"
(http://labs.trolltech.com/blogs/2009/01/26/creating-thumbnail-preview)

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--- Comment #17 from Gilles Caulier <caulier gilles gmail com>  2010-02-06 15:06:31 ---
Marcel,

Yes, it's clear that libpgf is not the problem here. Great to see...

Gilles Caulier

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--- Comment #18 from  <falolaf gmail com>  2010-02-07 09:01:25 ---
Can this explain that thumbnails from RAW images seems to be unaffected?

/Anders

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--- Comment #19 from Marcel Wiesweg <marcel wiesweg gmx de>  2010-02-07 14:25:26 ---
It may be that RAW thumbnails are generated from a preview which is already
smaller, or that for some other reason the scanning optimization actually works
well for these cases.

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