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

Mikolaj Machowski mikmach at wp.pl
Wed Jun 21 21:29:18 BST 2006

Dnia środa, 21 czerwca 2006 19:06, Caulier Gilles napisał:
> Le Mercredi 21 Juin 2006 16:08, Mikolaj Machowski a écrit :
> > Dnia środa, 21 czerwca 2006 13:46, Gilles Caulier napisał:
> > > SVN commit 553524 by cgilles:
> > >
> > > digikam from trunk : digiKam KIO slave image preview extractor use
> > > now the new DMetadata IPTC image preview extraction method ! It's
> > > very fast !!!
> >
> > Don't know how for RAW files but preview speed for JPEG files is
> > much slower...
> Because, if no preveiw data is found in IPTC tags, the whole image is
> loaded uing Qt.

So, why previous method was faster? Weren't image loaded?

> There is somthing missing for that : the Exif makernote preview tag
> extraction. Exiv2 need to be improved for that. It's planed for the next
> release

What about generating necessary method by Digikam/Image Editor?
> > 2. What is sampling factor? In most systems 1x2 (or lower) is default
> >    but offers significantly reduced quality for modest size gains
> >    comparing to 1x1.
> sampling factor ?

From ImageMagick man:

-sampling-factor <horizontal_factor>x<vertical_factor>
      sampling	factors	 used  by  JPEG	 or  MPEG-2  encoder  and  YUV

      This option specifies the sampling factors to  be	 used  by  the
      JPEG  encoder  for chroma downsampling.  If this option is omit-
      ted, the JPEG library will use its  own  default	values.	  When
      reading  or  writing  the	 YUV  format  and when writing the M2V
      (MPEG-2) format, use -sampling-factor 2x1 to specify  the	 4:2:2
      downsampling  method.  To use the same sampling factors as those
      found by the JPEG decoder, use  the  -define  jpeg:preserve-set-
      tings flag.


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