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diff --git a/octave_packages/image-1.0.15/imdither.m b/octave_packages/image-1.0.15/imdither.m
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+## Copyright (C) 2009 Sergey Kirgizov
+##
+## This program is free software; you can redistribute it and/or
+## modify it under the terms of the GNU General Public License
+## as published by the Free Software Foundation; either version 3
+## of the License, or (at your option) any later version.
+## 
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {[@var{Y}, @var{newmap}] = } imdither (@var{img})
+## @deftypefnx {Function File} {[@var{Y}, @var{newmap}] = } imdither (@var{img}, @
+## @var{colors})
+## @deftypefnx {Function File} {[@var{Y}, @var{newmap}] = } imdither (@var{img}, @
+## @var{colors}, @var{dithtype})
+## @deftypefnx {Function File} {[@var{Y}, @var{newmap}] = } imdither (@var{img}, @
+## @var{map})
+## @deftypefnx {Function File} {[@var{Y}, @var{newmap}] = } imdither (@var{img}, @
+## @var{map}, @var{colors})
+## @deftypefnx {Function File} {[@var{Y}, @var{newmap}] = } imdither(@var{img}, @
+## @var{map}, @var{colors}, @var{dithtype})
+## Reduce the number a colors of rgb or indexed image.
+##
+## Note: this requires the ImageMagick "convert" utility.
+## get this from www.imagemagick.org if required
+## additional documentation of options is available from the
+## convert man page.
+##
+## where
+## @var{dithtype} is a value from list:
+## 
+## @itemize @bullet
+## @item "None"
+## @item "FloydSteinberg" (default)
+## @item "Riemersma"
+## @end itemize 
+##
+## @var{colors} is a maximum number of colors in result map
+##
+## TODO: Add facility to use already created colormap over "-remap" option
+##
+## BUGS: This function return a 0-based indexed images 
+## when colormap size is lower or equals to 256 like at cmunique code
+## @seealso{cmunique}
+##
+## @end deftypefn
+
+function [Y,newmap] = imdither(im,p1,p2,p3)
+  
+  colors="256";
+  dithtype="FloydSteinberg";
+  if  ( nargin < 1 )
+    usage([ ...
+       "imdither( rgb )\n", ...
+       "imdither( rgb,colors )\n", ...
+       "imdither( rgb,colors,dithtype )\n", ...
+       "imdither( img,map )\n", ...
+       "imdither( img,map,colors )\n", ...
+       "imdither( img,map,colors,dithtype )\n"       
+       ]);
+  endif
+
+  fname = [tmpnam(),".ppm"];
+  if (nargin == 1 || isscalar(p1))
+                # rgb
+    if (nargin >= 2)
+      colors=sprintf("%d",p1);
+      if (nargin >= 3)
+    dithtype=p2;
+      endif
+    endif
+    opts=["-colors ",colors;"-dither ",dithtype];
+    imwrite(fname,im(:,:,1),im(:,:,2),im(:,:,3),opts);
+    [Y,newmap]=cmunique(imread(fname));        
+    delete(fname);
+  else    
+    if (nargin <= 1)
+      usage([ ...
+         "imdither( rgb )\n", ...
+         "imdither( rgb,colors )\n", ...
+         "imdither( rgb,colors,dithtype )\n", ...
+         "imdither( img,map )\n", ...
+         "imdither( img,map,colors )\n", ...
+         "imdither( img,map,colors,dithtype )\n"       
+         ]);
+    endif
+                # indexed
+    if (nargin >= 3)
+      colors=sprintf("%d",p2);
+      if (nargin >= 4)
+    dithtype=p3;
+      endif
+    endif
+    opts=["-colors ",colors;"-dither ",dithtype];
+    im (rows(p1)<=256)
+    imwrite(fname,im,(p1+1),opts);
+    [Y,newmap]=cmunique(imread(fname));    
+    delete(fname);
+  endif
+endfunction