Histogram White Spike bug in Brightness Contrast Filter dialog

William Steidtmann billstei at hbci.com
Tue Nov 30 02:33:44 CET 2010

Attached is a patch that eliminates the KisHistogram::KisHistogram() 
constructor that does not pass a "bounds" parameter when using a paint 
device, and modifies all calls to the new KisHistogram constructor that 
does use "bounds".  Most of these calls are (temporarily) passing 
exactBounds (and so this code does not change behaviour there), with the 
exception of the Brightness Contrast filter, which now passes image 
bounds, and thus fixes the White Spike bug in the Brightness Contrast 
filter dialog.  This is very much the same as the Levels Filter 
histogram patch (see Commit #1200357).

To recreate the (pre-patch) bug:

1) Create a 10x10 image, 8 bit sRGB.
2) Set the color to a dark gray 92,92,92.
3) Use a pixel brush to paint all (most) of the image this dark gray.
4) Use menu Filter->Adjust->Brightness/Contrast curve...
5) Note that the graph has little or no indication (count) in the second 
quadrant where this dark gray should be.

After the patch, the second quadrant in step 5) will have an appropriate 
pixel count.

William Steidtmann
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