[Bug 193967] New: VERY fast loading of thumbnails [PATCH]

https://bugs.kde.org/show_bug.cgi?id=193967

           Summary: VERY fast loading of thumbnails [PATCH]
           Product: digikam
           Version: unspecified
          Platform: Compiled Sources
        OS/Version: Linux
            Status: NEW
          Severity: wishlist
          Priority: NOR
         Component: Albums GUI
        AssignedTo: [hidden email]
        ReportedBy: [hidden email]


Version:            (using Devel)
Compiler:          gcc4.3.2
OS:                Linux
Installed from:    Compiled sources

With this simple patch loading of thumbnails is much, much faster. Of course it
comes with price - slightly lower quality of thumbs (but only on display,
generated thumbnails are of good quality).

It is done by simple change from SmoothTranformation to FastTransformation.

I understand that this trade off isn't good for everyone but digiKam experience
becomes much smoother after removing of Smooth transformation ;)

Several possible solutions:
- use that patch as is and accept slightly lower quality (really visible only
with smallest thumbnails of 80px - and really, who could expect super quality
from those thumbs ;)
- make option in config dialog a) lower quality of thumbs, faster loading b)
high quality of thumbs, slower browsing of albums
- load thumbnails in two passes: first time with FastTransformation, second,
after eg. 2-3 seconds of inactivity with Smooth transformation

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Mikolaj Machowski <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Version|unspecified                 |0.11.0-svn




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--- Comment #1 from Mikolaj Machowski <mikmach wp pl>  2009-05-25 01:30:05 ---
Created an attachment (id=33985)
 --> (http://bugs.kde.org/attachment.cgi?id=33985)
%s/Smooth/Fast/ Transformation

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--- Comment #2 from Mikolaj Machowski <mikmach wp pl>  2009-05-25 02:33:58 ---
I was too fast. First replace is harmful -> it generates lower quality thumbs.
Have to test it more - but second part is still valid!

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[Gilles Caulier-4]

https://bugs.kde.org/show_bug.cgi?id=193967


Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Albums GUI                  |Thumbnails




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Gilles Caulier <[hidden email]> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED




--- Comment #3 from Gilles Caulier <caulier gilles gmail com>  2009-05-25 06:30:47 ---
SVN commit 972480 by cgilles:

optimize QImage scaled 2nd pass to use fast transform instead smooth transform.
Quality still here.
BUG: 193967


 M  +7 -8      thumbnailcreator.cpp  
 M  +3 -0      thumbnailcreator_p.h  


WebSVN link: http://websvn.kde.org/?view=rev&revision=972480

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--- Comment #4 from Andi Clemens <andi clemens gmx net>  2009-05-25 09:40:20 ---
For me thumbs have bad quality now, Gilles i guess yours are ok because they
have been already created before?
What when removing .thumbnails folder?

I remember some blog entry on the QtLabs homepage where some way was introduced
to have good AND fast scalings. Need to search for this...

Andi

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--- Comment #5 from Andi Clemens <andi clemens gmx net>  2009-05-25 09:44:43 ---
Ah, here it is:
http://labs.trolltech.com/blogs/2009/01/26/creating-thumbnail-preview/

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--- Comment #6 from Andi Clemens <andi clemens gmx net>  2009-05-25 09:50:15 ---
Also, this cheat scale seems to be even faster then FastTransformation, but
looks like SmoothTransformation.

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--- Comment #7 from Gilles Caulier <caulier gilles gmail com>  2009-05-25 09:52:42 ---
Andi,

Of course, i have tested to remove ./thumbnails (:=))) It still good quality
without anti-aliasing if thumbs size is less than 256. At 256, smoothscale
version is used (from cache).

What do you mean by bad quality exactly ? Can you take a screenshot ?

Gilles Caulier

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--- Comment #8 from Gilles Caulier <caulier gilles gmail com>  2009-05-25 10:00:32 ---
Andi,

The question is : why i cannot see any signifiant differences here when size <
256 ?

Gilles

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--- Comment #9 from Andi Clemens <andi clemens gmx net>  2009-05-25 10:31:37 ---
Created an attachment (id=33988)
 --> (http://bugs.kde.org/attachment.cgi?id=33988)
FastTransformation - 137px thumbnail size

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--- Comment #10 from Andi Clemens <andi clemens gmx net>  2009-05-25 10:32:12 ---
Created an attachment (id=33989)
 --> (http://bugs.kde.org/attachment.cgi?id=33989)
256px thumbnail size

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--- Comment #11 from Andi Clemens <andi clemens gmx net>  2009-05-25 10:33:18 ---
As you can see in the above screenshots, the outlines are very jaggy.

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--- Comment #12 from Mikolaj Machowski <mikmach wp pl>  2009-05-25 16:11:03 ---
Andi - for me 256px thumbnail is smooth as previously. Smaller thumbs *are*
jagged but not to such extent. Only in 80px I see something like on your
screenshot and only on pictures with high contrast. What is your graphic card
and drivers? (I have old Nvidia with legacy, proprietary OpenGL drivers)

Gilles - maybe some misunderstanding? My idea/patch was only simple replacement
of Smooth with Fast, there is no second pass and writing of it is beyond my
capabilities.

Personally this trade off - lower quality of thumbnails for faster loading of
them is preferable - even welcomed with enthusiasm. Previously loading of whole
screen of thumbs could take 4-5 seconds. Now filling the screen with thumbs
take about 1 second. Judging from number of wishes for preloading of thumbs
speed is important for users.

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--- Comment #13 from Andi Clemens <andi clemens gmx net>  2009-05-25 16:20:55 ---
1 second? When generating the thumbnails? Then my system is crap, although I
have a MacBookPro Core 2 Duo. It takes 8 seconds and more for one page
(smallest thumbsize, approx 40 thumbs per page).
But if you mean the loading of the thumbs that are already cached / generated,
this is not faster for me.
The approach in the above Qt Labs blog entry should be even faster then
FastTransform AND look better, so maybe we should try this method?

Andi

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--- Comment #14 from Mikolaj Machowski <mikmach wp pl>  2009-05-25 17:41:53 ---
Below I will attach copy'n'paste patch with "cheat" method from Ariya.

1) his method doesn't care about aspect ratio so you will see squares but as
quick tool for tests it is enough
2) it is slightly slower than fast transformation - he probably tested it on
big images where it is easier to gain performance, we are going only for
scaling 256px downwards to 80px; on my screen smallest thumbs (55 pieces) take
3 seconds to fill the screen; It would be interesting to see what this method
gives for generation of real thumbs; all times are for already generated thumbs
and I see difference between loading of pregenerated thumbs before and now
(Gilles patch doesn't touch generation of thumbs at all)
3) my computer: Sempron 2200, 756MB RAM (233 MHz), GeForce2 MX 400; Qt4.5.1,
KDE4.3svn
4) bit tricky legal issues: file of origin where cheatScale is coming from is
under GPL2 or 3, while thumbnailcreator.cpp is GPL2+
5) what is taking so much time is loading of thumbnails in sequence; would it
be possible to load them simultaneously (thread per thumb or at least few
threads per whole screen)?

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--- Comment #15 from Mikolaj Machowski <mikmach wp pl>  2009-05-25 17:44:05 ---
Created an attachment (id=33995)
 --> (http://bugs.kde.org/attachment.cgi?id=33995)
hack'n'slash patch for 'cheatscale'

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--- Comment #16 from Marcel Wiesweg <marcel wiesweg gmx de>  2009-05-25 18:03:48 ---
We should be careful, if we use FastTransformation and users notice that
thumbnails look "bad" then it makes a really bad impression on the average
user.
On my system, thumbnail loading is not significantly bothering me at all.
Creating takes its time, but loading is fast enough. I usually use thumbnail
size 160 and I never "wait" for thumbnails to appear once they are created.

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--- Comment #17 from Andi Clemens <andi clemens gmx net>  2009-05-25 18:14:03 ---
Yes, here too. I don't see a difference once the thumbs are generated. The
creation is slow, this could be faster (maybe with this cheat method, so it
would also look nice?)

Andi

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