[Digikam-devel] [Bug 149578] New: libjpeg JPEG subsampling setting is not user-controlable

[Jean-Marc Liotier]

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http://bugs.kde.org/show_bug.cgi?id=149578         
           Summary: libjpeg JPEG subsampling setting is not user-controlable
           Product: digikam
           Version: 0.9.1
          Platform: Ubuntu Packages
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: wishlist
          Priority: NOR
         Component: Image Editor
        AssignedTo: digikam-devel kde org
        ReportedBy: jim liotier org


Version:           0.9.1 (using KDE KDE 3.5.6)
Installed from:    Ubuntu Packages
OS:                Linux

This but is basically a reopening of bug #130996. Bug #130996 has been marked as a duplicate of #123649 but it was not the case : #123649 specifically called for the inclusion of the JPEG "quality" factor (an integer between 0 and 100) into the "save as" dialog whereas #130996 also asked for other controls including subsampling.

#130996 expressed exactly what I felt, so I am going to quote it :

"I am really interested in having easy control over Subsampling.  This option was originally in jpeg to help further compress large files by averaging out similar colors, in able to reduce the jpeg file size.  The default value for libjpeg is 2x2, 1x1, 1,1 .  Digikam currently does not set this option, and therefore uses this default.  Breifly, this default option throws away half of the color information, perhaps great for vidio compression, but not for todays high-quality color photography".

Just like the reporter of #130996 I come from a Gimp background and I miss control over subsampling for the same reasons.

You can take a look at Gimp's "save as" JPEG dialog and you will find everything. I understand that Digikam's goal is to be as simple as possible, but JPEG subsampling is not a needlessly complicated tweak : it is the second most important parameter in controlling JPEG's quality.