--- a/inst/imhist.m
+++ b/inst/imhist.m
@@ -1,8 +1,10 @@
-## Copyright (C) 1999,2000  Kai Habel
+## Copyright (C) 1999,2000 Kai Habel <kai.habel@gmx.de>
+## Copyright (C) 2000 Paul Kienzle
+## Copyright (C) 2011 Carnë Draug <carandraug+dev@gmail.com>
 ##
 ## 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
+## 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,
@@ -14,58 +16,80 @@
 ## along with this program; If not, see <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {} imhist (@var{I},@var{n})
-## @deftypefnx {Function File} {} imhist (@var{I})
-## @deftypefnx {Function File} {} imhist (@var{X},@var{cmap})
-## @deftypefnx {Function File} {[@var{n,x}] = } imhist (...)
-## Shows the histogram of an image using hist.
-## @seealso{hist}
+## @deftypefn {Function File} {} imhist (@var{I})
+## @deftypefnx {Function File} {} imhist (@var{I}, @var{n})
+## @deftypefnx {Function File} {} imhist (@var{X}, @var{cmap})
+## @deftypefnx {Function File} {[@var{counts}, @var{x}] =} imhist (@dots{})
+## Shows the histogram of an image @var{I}.
+##
+## The second argument can either be @var{n}, a scalar that specifies the number
+## of bins; or @var{cmap}, a colormap in which case @var{X} is expected to be
+## an indexed image. If not specified, @var{n} defauls to 2 for binary images,
+## and 256 for grayscale images.
+##
+## If output is requested, @var{counts} is the number of counts for each bin and
+## @var{x} is a range for the bins so that @code{stem (@var{x}, @var{counts})} will
+## show the histogram.
+## @seealso{hist, histc, histeq}
 ## @end deftypefn
 
-## Author:	Kai Habel <kai.habel@gmx.de>
-## July 2000 : Paul Kienzle code simplification for hist() call.
-
-function [varargout] = imhist (I, b)
+function [nn, bins] = imhist (I, b)
 
   if (nargin < 1 || nargin > 2)
     print_usage();
-  endif
 
-  b_is_colormap = 0;
+  elseif (nargin == 1)
+    if (islogical(I))
+      bins = 0:1;
+    else
+      bins = 0:255;
+    endif
 
-  if (nargin == 2)
-    if (ismatrix (b))
-      b_is_colormap = (columns (b) == 3);
+  elseif (nargin == 2)
+    ## A matrix with 3 columns is a colormap so...
+    if (ismatrix (b) && columns (b) == 3)
+      using_colormap = true;
+      ## if using a colormap, image must be an indexed image
+      if (!isind(I))
+        error ("second argument is a colormap but image is not indexed");
+      endif
+      max_idx = max (I(:));
+      bins    = 0:rows(b)-1;
+      if (max_idx > bins(end))
+        warning ("largest index exceeds length of colormap");
+      endif
+    elseif (isnumeric (b) && isscalar (b) && fix(b) == b)
+      using_colormap = false;
+      bins = 0:b-1;
+    else
+      error ("second argument should either be a positive integer scalar or a colormap");
     endif
   endif
 
-  if (b_is_colormap)
-    ## assuming I is an indexed image
-    ## b is colormap
-    max_idx = max (max (I));
-    bins = rows (b);
-    if (max_idx > bins)
-      warning ("largest index exceedes length of colormap");
+  ## matlab returns bins as one column and not one row so we transpose the range
+  bins = bins';
+
+  ## XXX at the moment, this function is not working at all, at least for
+  ## grayscale images. I'm assuming that the code will at least be working for
+  ## indexed images and colormaps so I'm leaving the original code for those
+  ## cases and use only the "new" code when "using_colormap" is false
+  ## Carnë Draug 10/11/2011
+  if (nargout == 0)
+    if (using_colormap)
+      hist (I(:), bins);
+    else
+      [nn] = histc (I(:), bins);
+      stem (bins, nn);
     endif
   else
-    ## assuming I is an intensity image
-    ## b is number of bins
-    if (nargin == 1)
-      bins = 256;
+    if (using_colormap)
+      [nn,bins] = hist (I(:), bins);
     else
-      bins = b;
+      [nn] = histc (I(:), bins);
     endif
 
-    ## scale image to range [0,1]
-    I = mat2gray (I);
+    vr_val_cnt = 1;
+    varargout{vr_val_cnt++} = nn;
+    varargout{vr_val_cnt++} = bins;
   endif
-  
-  if (nargout == 2)
-    [nn,xx] = hist (I(:), bins);
-    vr_val_cnt = 1; varargout{vr_val_cnt++} = nn;
-    varargout{vr_val_cnt++} = xx;
-  else
-    hist (I(:), bins);
-  endif
-
 endfunction