Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/image-1.0.15/grayslice.m b/octave_packages/image-1.0.15/grayslice.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{X} =} grayslice (@var{I},@var{n})
+## @deftypefnx {Function File} {@var{X} =} grayslice (@var{I},@var{v})
+## creates an indexed image @var{X} from an intensitiy image @var{I}
+## using multiple threshold levels.
+## A scalar integer value @var{n} sets the levels to
+## @example
+## 
+## @group
+## 1  2       n-1
+## -, -, ..., ---
+## n  n        n
+## @end group
+## @end example
+##
+## X = grayslice(I,5);
+##
+## For irregular threshold values a real vector @var{v} can be used.
+## The values must be in the range [0,1].
+##
+## @group
+## X = grayslice(I,[0.1,0.33,0.75,0.9])
+## @end group
+##
+## @seealso{im2bw}
+## @end deftypefn
+
+## Author:     Kai Habel <kai.habel@gmx.de>
+## Date:       03. August 2000
+
+function X = grayslice (I, v)
+
+  if (nargin != 2)
+    usage ("grayslice(...) number of arguments must be 1 or 2");
+  endif
+
+  if (is_scalar(v) && (fix(v) == v))
+
+    v = (1:v - 1) / v;
+
+  elseif (isvector(v))
+
+    if (any (v < 0) || (any (v > 1)))
+      error ("slice vector must be in range [0,1]")
+    endif
+    v = [0,v,1];
+  else
+
+    usage("second argument");
+
+  endif
+
+  [r, c] = size (I);
+  [m, n] = sort ([v(:); I(:)]);
+  lx = length (v);
+  o = cumsum (n <= lx);
+  idx = o (find(n>lx));
+  [m, n] = sort (I(:));
+  [m, n] = sort (n);
+  X = reshape (idx(n), r, c);
+
+endfunction