[Digikam-devel] [Bug 142571] Auto-exposure result is different from the preview

[Jörg Kühne]

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http://bugs.kde.org/show_bug.cgi?id=142571         




------- Additional Comments From joerg.kuehne lycos de  2007-03-08 22:34 -------
The Auto-exposure values calculated from prewiew picture are different from the values of the original picture (black/white point). 
Try the following patch. It works fine for me.

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Index: libs/whitebalance/whitebalance.cpp
===================================================================
--- libs/whitebalance/whitebalance.cpp	(revision 640698)
+++ libs/whitebalance/whitebalance.cpp	(working copy)
 @ -179,18 +179,13  @
        
     // Calculate optimal exposition and black level 
     
-    int    stop, i, scale, w, h;
-    double sum;
+    double sum, stop;
+    int i;
     uint   rgbMax = sb ? 65536 : 256;
     
-    w     = width  / 400;
-    h     = height / 400;
-    scale = QMAX(w, h);
-    scale = QMAX(1, scale);
-    
     // Cutoff at 0.5% of the histogram.
     
-    stop = ((uint)(width / scale)*(uint)(height / scale)) / 200;
+    stop = width * height / 200.0;
     
     for (i = rgbMax, sum = 0; (i >= 0) && (sum < stop); i--)
         sum += histogram->getValue(Digikam::ImageHistogram::ValueChannel, i);
 @ -198,10 +193,6  @
     expo = -log((float)(i+1) / rgbMax) / log(2);
     DDebug() << "White level at:" << i << endl;
     
-    // Cutoff at 0.5% of the histogram. 
-    
-    stop = ((uint)(width / scale)*(uint)(height / scale)) / 200;
-    
     for (i = 1, sum = 0; (i < (int)rgbMax) && (sum < stop); i++)
         sum += histogram->getValue(Digikam::ImageHistogram::ValueChannel, i);

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Jörg