I once wrote a path for it, this included the possibility of disabling the histogram correction (by setting the values out of range).
It seems that a more recent patch reversed this option.
Probably the out of range option was not the best way of implementing it, however the function does make sense
for line-art and B&W photo's see bug #72862.

Revision *16861* <http://svn.gnome.org/viewcvs/gimp?view=revision&revision=16861> - (view <http://svn.gnome.org/viewcvs/gimp/trunk/plug-ins/common/despeckle.c?revision=16861&view=markup>) (annotate <http://svn.gnome.org/viewcvs/gimp/trunk/plug-ins/common/despeckle.c?annotate=16861>) - [select for diffs] <http://svn.gnome.org/viewcvs/gimp/trunk/plug-ins/common/despeckle.c?r1=16861&view=log>

2005-03-11  Sven Neumann  <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>

        * plug-ins/common/despeckle.c: test intensity against white and
        black level, not only the red channel. Improved border behavior.
        Iterate over the pixels row-by-row, instead of jumping through the
        data column-wise.

...

Revision *15374* 
<http://svn.gnome.org/viewcvs/gimp?view=revision&revision=15374> -
2004-10-30  Sven Neumann  <[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>>

        * plug-ins/common/despeckle.c: applied a patch from Geert Jordaens
        that improves the Despeckle algorithm. See bug #72862 
<http://bugzilla.gnome.org/show_bug.cgi?id=72862>.

Right now I don't have the tme to followup a bug report or create a complete 
patch.

         for (v = ymin; v < ymax; v++)
           {
             gint off2 = v * width * bpp;

             for (u = xmin, off2 += xmin * bpp; u < xmax; u++, off2 += bpp)
               {
                 guchar value = pixel_luminance (src + off2, bpp);

/*                if (value < black_level) Allow no histogram correction on line 
art or b&w*/
                 if (value < black_level && filter_type & FILTER_ADAPTIVE)
                   {
                     hist0++;
                   }

/*                else if (value > white_level) Allow no histogram correction on 
line art or b&w*/
                 else if (value > white_level && filter_type & FILTER_ADAPTIVE)
                   {
                     hist255++;
                   }
                 else
                   {
                     buf[count]  = src + off2;
                     ibuf[count] = value;
                     count++;
                   }
               }
           }



Geert Jordaens


Luis A. Florit wrote:
Pals,

    I reported this bug in this list some time ago, and got no
answer (I think), and the 2.3.16 version still has the same bug:
The despeckle plugin shifts the image one pixel to the right,
and one to the bottom. Consequently, it is essentially useless.
If you draw in the middle of a white background a black cross
like this:

 x
xxx
 x

and run the despeckle plugin with radius 1, you get this asymmetric
output:

 x
xxx
 xx

    Thanks,

        Luis.

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