## Copyright (C) 2010 Soren Hauberg
##
## 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.
##
## 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{props} = } regionprops (@var{BW})
## @deftypefnx {Function File} {@var{props} = } regionprops (@var{BW}, @var{properties}, @dots{})
## Compute object properties in a binary image.
##
## @code{regionprops} computes various properties of the individual objects (as
## identified by @code{bwlabel}) in the binary image @var{BW}. The result is a
## structure array containing an entry per property per object.
##
## The following properties can be computed.
##
## @table @t
## @item "Area"
## The number of pixels in the object.
## @item "EulerNumber"
## @itemx "euler_number"
## The Euler number of the object (see @code{bweuler} for details).
## @item "BoundingBox"
## @itemx "bounding_box"
## The bounding box of the object. This is represented as a 4-vector where the
## first two entries are the @math{x} and @math{y} coordinates of the upper left
## corner of the bounding box, and the two last entries are the width and the
## height of the box.
## @item "Extent"
## The area of the object divided by the area of the bounding box.
## @item "Perimeter"
## The length of the boundary of the object.
## @item "Centroid"
## The center coordinate of the object.
## @item "PixelIdxList"
## @itemx "pixel_idx_list"
## The indices of the pixels in the object.
## @item "FilledArea"
## @itemx "filled_area"
## The area of the object including possible holes.
## @item "PixelList"
## @itemx "pixel_list"
## The actual pixel values inside the object. This is only useful for grey scale
## images.
## @item "FilledImage"
## @itemx "filled_image"
## A binary image with the same size as the object's bounding box that contains
## the object with all holes removed.
## @item "Image"
## An image with the same size as the bounding box that contains the original pixels.
## @item "MaxIntensity"
## @itemx "max_intensity"
## The maximum intensity inside the object.
## @item "MinIntensity"
## @itemx "min_intensity"
## The minimum intensity inside the object.
## @item "WeightedCentroid"
## @itemx "weighted_centroid"
## The centroid of the object where pixel values are used as weights.
## @item "MeanIntensity"
## @itemx "mean_intensity"
## The mean intensity inside the object.
## @item "PixelValues"
## @itemx "pixel_values"
## The pixel values inside the object represented as a vector.
## @end table
##
## The requested properties can either be specified as several input arguments
## or as a cell array of strings. As a short-hand it is also possible to give
## the following strings as arguments.
##
## @table @t
## @item "basic"
## The following properties are computed: @t{"Area"}, @t{"Centroid"} and @t{"BoundingBox"}.
## @item "all"
## All properties are computed.
## @end table
##
## If no properties are given, @t{basic} is assumed.
## @seealso{bwlabel, bwperim, bweuler}
## @end deftypefn

function retval = regionprops (bw, varargin)
  ## Check input
  if (nargin < 1)
    error ("regionprops: not enough input arguments");
  endif
  
  if (!ismatrix (bw) || ndims (bw) != 2)
    error ("regionprops: first input argument must be a NxM matrix");
  endif

  if (numel (varargin) == 0)
    properties = "basic";
  elseif (numel (varargin) == 1 && iscellstr (varargin {1}))
    properties = varargin {1};
  elseif (iscellstr (varargin))
    properties = varargin;
  else
    error ("regionprops: properties must be a cell array of strings");
  endif
    
  if (ischar (properties) && strcmpi (properties, "basic"))
    properties = {"Area", "Centroid", "BoundingBox"};
  elseif (ischar (properties) && strcmpi (properties, "all"))
    properties = {"area", "eulernumber", "boundingbox", "extent", "perimeter", ...
                  "centroid", "pixelidxlist", "filledarea", "pixellist",       ...
                  "filledimage", "image", "maxintensity", "minintensity",      ...
                  "weightedcentroid", "meanintensity", "pixelvalues"};
  elseif (!iscellstr (properties))
    error ("%s %s", "regionprops: properties must be specified as a list of",
           "strings or a cell array of strings");
  endif

  ## Get a labelled image
  if (!islogical (bw) && all (bw >= 0) && all (bw == round (bw)))
    L = bw; # the image was already labelled
    num_labels = max (L (:));
  else
    [L, num_labels] = bwlabel (bw);
  endif
  
  ## Compute the properties
  retval = struct ();
  for k = 1:numel (properties)
    switch (lower (properties {k}))
      case "area"
        for k = 1:num_labels
          retval (k).Area = local_area (L == k);
        endfor
        
      case {"eulernumber", "euler_number"}
        for k = 1:num_labels
          retval (k).EulerNumber = bweuler (L == k);
        endfor

      case {"boundingbox", "bounding_box"}
        for k = 1:num_labels
          retval (k).BoundingBox = local_boundingbox (L == k);
        endfor

      case "extent"
        for k = 1:num_labels
          bb = local_boundingbox (L == k);
          area = local_area (L == k);
          retval (k).Extent = area / (bb (3) * bb (4));
        endfor

      case "perimeter"
        for k = 1:num_labels
          retval (k).Perimeter = sum (bwperim (L == k) (:));
        endfor

      case "centroid"
        for k = 1:num_labels
          [Y, X] = find (L == k);
          retval (k).Centroid = [mean(X), mean(Y)];
        endfor

      case {"pixelidxlist", "pixel_idx_list"}
        for k = 1:num_labels
          retval (k).PixelIdxList = find (L == k);
        endfor
      
      case {"filledarea", "filled_area"}
        for k = 1:num_labels
          retval (k).FilledArea = sum (bwfill (L == k, "holes") (:));
        endfor

      case {"pixellist", "pixel_list"}
        for k = 1:num_labels
          [Y, X] = find (L == k);
          retval (k).PixelList = [X, Y];
        endfor

      case {"filledimage", "filled_image"}
        for k = 1:num_labels
          retval (k).FilledImage = bwfill (L == k, "holes");
        endfor

      case "image"
        for k = 1:num_labels
          tmp = (L == k);
          [R, C] = find (tmp);
          retval (k).Image = tmp (min (R):max (R), min (C):max (C));
        endfor

      case {"maxintensity", "max_intensity"}
        for k = 1:num_labels
          retval (k).MaxIntensity = max (bw (L == k) (:));
        endfor
    
      case {"minintensity", "min_intensity"}
        for k = 1:num_labels
          retval (k).MaxIntensity = min (bw (L == k) (:));
        endfor
    
      case {"weightedcentroid", "weighted_centroid"}
        for k = 1:num_labels
          [Y, X] = find (L == k);
          vals = bw (L == k) (:);
          vals /= sum (vals);
          retval (k).WeightedCentroid = [dot(X, vals), dot(Y, vals)];
        endfor

      case {"meanintensity", "mean_intensity"}
        for k = 1:num_labels
          retval (k).MaxIntensity = mean (bw (L == k) (:));
        endfor
        
      case {"pixelvalues", "pixel_values"}
        for k = 1:num_labels
          retval (k).PixelValues = bw (L == k)(:);
        endfor
    
      case "orientation"
        for k = 1:num_labels
          [Y, X] = find (L == k);
          if (numel (Y) > 1)
            C = cov ([X(:), Y(:)]);
            [V, lambda] = eig (C);
            [max_val, max_idx] = max (diag (lambda));
            v = V (:, max_idx);
            retval (k).Orientation = 180 - 180 * atan2 (v (2), v (1)) / pi;
          else
            retval (k).Orientation = 0; # XXX: What does the other brand do?
          endif
        endfor
        
      %{
      case "majoraxislength"
        for k = 1:num_labels
          [Y, X] = find (L == k);
          if (numel (Y) > 1)
            C = cov ([X(:), Y(:)]);
            lambda = eig (C);
            retval (k).MajorAxisLength = (max (lambda));
          else
            retval (k).MajorAxisLength = 1;
          endif
        endfor
        
      case "minoraxislength"
        for k = 1:num_labels
          [Y, X] = find (L == k);
          if (numel (Y) > 1)
            C = cov ([X(:), Y(:)]);
            lambda = eig (C);
            retval (k).MinorAxisLength = (min (lambda));
          else
            retval (k).MinorAxisLength = 1;
          endif
        endfor
      %}
      
      #case "extrema"
      #case "convexarea"      
      #case "convexhull"
      #case "solidity"
      #case "conveximage"
      #case "subarrayidx"
      #case "eccentricity"
      #case "equivdiameter"

      otherwise
        error ("regionprops: unsupported property '%s'", properties {k});
    endswitch
  endfor
endfunction

function retval = local_area (bw)
  retval = sum (bw (:));
endfunction

function retval = local_boundingbox (bw)
  [Y, X] = find (bw);
  retval = [min(X)-0.5, min(Y)-0.5, max(X)-min(X)+1, max(Y)-min(Y)+1];
endfunction