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

[Arnd Baecker]

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------- Additional Comments From arnd.baecker web de  2007-09-07 16:40 -------
Ad #c15 and #c17: just in case, it seems that the
code downloadable at http://www.programmersheaven.com/download/17054/download.aspx
could be used as basis for the detection of the jpeg compression level.
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2007-09-08 17:49 -------
SVN commit 709928 by cgilles:

kipi-plugins RAW converter : set JPEG subsampling factor to Medium.
CCBUGS: 149578


 M  +11 -4     rawdecodingiface.cpp  


--- branches/extragear/kde3/libs/kipi-plugins/rawconverter/rawdecodingiface.cpp #709927:709928
 @ -223,10 +223,17  @
             cinfo.input_components = 3;
             cinfo.in_color_space   = JCS_RGB;
             jpeg_set_defaults(&cinfo);
-            // B.K.O #130996: set horizontal and vertical Subsampling factor
-            // to 1 for a best quality of color picture compression.
-            cinfo.comp_info[0].h_samp_factor = 1;
-            cinfo.comp_info[0].v_samp_factor = 1;
+
+            // B.K.O #149578: set encoder horizontal and vertical chroma subsampling
+            // factor to 2x1, 1x1, 1x1 (4:2:2) : Medium subsampling.
+            // See this page for details: http://en.wikipedia.org/wiki/Chroma_subsampling 
+            cinfo.comp_info[0].h_samp_factor = 2;
+            cinfo.comp_info[0].v_samp_factor = 1;
+            cinfo.comp_info[1].h_samp_factor = 1;
+            cinfo.comp_info[1].v_samp_factor = 1;
+            cinfo.comp_info[2].h_samp_factor = 1;
+            cinfo.comp_info[2].v_samp_factor = 1;
+
             jpeg_set_quality(&cinfo, 100, true);
             jpeg_start_compress(&cinfo, true);
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[Gilles Caulier-4]

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------- Additional Comments From caulier.gilles gmail com  2007-09-08 17:52 -------
Jean marc,

Do you know another important settings to adjust image quality with JPEG encoder which is missing in digiKam ? If yes, please open a new file in this room...

Thanks in advance

Gilles
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