Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / image-1.0.15 / histeq.m

diff --git a/octave_packages/image-1.0.15/histeq.m b/octave_packages/image-1.0.15/histeq.m
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+## Copyright (C) 2000  Kai Habel
+##
+## 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 2 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.
+##
+## You should have received a copy of the GNU General Public License
+## along with this program; If not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} @var{J} = histeq (@var{I}, @var{n})
+## Histogram equalization of a gray-scale image. The histogram contains
+## @var{n} bins, which defaults to 64.
+##
+## @var{I}: Image in double format, with values from 0.0 to 1.0
+##
+## @var{J}: Returned image, in double format as well
+## @seealso{imhist}
+## @end deftypefn
+
+## Author:     Kai Habel <kai.habel@gmx.de>
+## Date:       08. August 2000
+## Modified-by: Jonas Wagner <j.b.w@gmx.ch>
+## Date:        11. February 2008
+
+function J = histeq (I, n)
+  if (nargin == 0)
+    print_usage();
+  elseif (nargin == 1)
+    n = 64;
+  endif
+
+  [r,c] = size(I); 
+  I = mat2gray(I);
+  [X,map] = gray2ind(I, n);
+  [nn,xx] = imhist(I, n);
+  Icdf = 1 / prod(size(I)) * cumsum(nn);
+  J = reshape(Icdf(X),r,c);
+  plot(Icdf,'b');
+  legend( 'Image Cumulative Density Function');
+endfunction