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

Gilles Caulier caulier.gilles at gmail.com
Sun Jun 14 07:53:30 BST 2009


2009/6/13 Mikolaj Machowski <mikmach at wp.pl>:
> On Saturday 13 June 2009 17:17:37 Gilles Caulier wrote:
>> 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.
>> > I have an average size of 11KB per thumbnail (db file size / number of
>> > stored thumbnails).
>> > Most important for me: Subjectively, loading is faster than with PGF.
>> > (With maximum number of icons visible - no sidebars, fullscreen, minimum
>> > thumbnail size - I can mouse wheel scroll at a reasonable fast speed
>> > without seeing missing thumbnails)
>>
>> Well, what better then ? JPEG as well with a compression ratio upper
>> than 75 (default Qt = 75) ? I recommend 85 instead...
>>
>> Mik, do you have tried 85 JPEG quality ? And in this case, DB will be
>> bigger : which size compared to PGF ?
>
> JPEG Qt default (probably 75): 147MB for 15000 images
> JPEG 85: 184MB
> PGF 4: 243MB


Thanks Mik,

And now, time mesurement. Not easy to do because PC timer is not fine...

in digikam/test, i just patched qtpgftest program to measure execusion
of encoding decoding PGF and JPEG image to/from byte array with same
DB conditions. Look result with small test.png image :

[gilles at localhost tests]$ identify test.png
test.png PNG 256x256 256x256+0+0 8-bit DirectClass 168kb

[gilles at localhost tests]$ ./qtpgftest.shell
<unknown program name>(6778)/ main: PGF Encoding time:  0.05  s
<unknown program name>(6778)/ main: PGF Decoding time:  0.03  s
<unknown program name>(6778)/ main: JPG Encoding time:  0.01  s
<unknown program name>(6778)/ main: JPG Decoding time:  0.01  s

If i retry test many time, with other image files, i can always see
JPG faster... JPEG compression is 85

Now, if i take a large image to test (a raw image converted to png):

[gilles at localhost tests]$ identify test.png
test.png PNG 3594x2397 3594x2397+0+0 16-bit DirectClass 24.58mb

[gilles at localhost tests]$ ./qtpgftest.shell
<unknown program name>(7467)/ main: PGF Encoding time:  3.61  s
<unknown program name>(7467)/ main: PGF Decoding time:  2.65  s
<unknown program name>(7467)/ main: JPG Encoding time:  0.66  s
<unknown program name>(7467)/ main: JPG Decoding time:  0.6  s

Gilles Caulier



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