%% Copyright (c) 2011, INRA
%% 2003-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
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%% -*- texinfo -*-
%% @deftypefn {Function File} {@var{h} = } drawEllipse (@var{elli})
%% @deftypefnx {Function File} {@var{h} = } drawEllipse (@var{xc}, @var{yc}, @var{ra}, @var{rb})
%% @deftypefnx {Function File} {@var{h} = } drawEllipse (@var{xc}, @var{yc}, @var{ra}, @var{rb}, @var{theta})
%% @deftypefnx {Function File} {@var{h} = } drawEllipse (@dots{}, @var{param}, @var{value})
%% Draw an ellipse on the current axis.
%%
%%   drawEllipse(ELLI);
%%   Draws the ellipse ELLI in the form [XC YC RA RB THETA], with center
%%   (XC, YC), with main axis of half-length RA and RB, and orientation
%%   THETA in degrees counted counter-clockwise.
%%   Puts all parameters into one single array.
%%
%%   drawEllipse(XC, YC, RA, RB);
%%   drawEllipse(XC, YC, RA, RB, THETA);
%%   Specifies ellipse parameters as separate arguments (old syntax).
%%
%%   drawEllipse(..., NAME, VALUE);
%%   Specifies drawing style of ellipse, see the help of plot function.
%%
%%   H = drawEllipse(...);
%%   Also returns handles to the created line objects.
%%
%%   -> Parameters can also be arrays. In this case, all arrays are supposed 
%%   to have the same size.
%%
%%   Example: 
%%   @example
%%   % Draw an ellipse centered in [50 50], with semi major axis length of
%%   % 40, semi minor axis length of 20, and rotated by 30 degrees.
%%     figure(1); clf; hold on;
%%     drawEllipse([50 50 40 20 30]);
%%     axis equal;
%% @end example
%%
%%   @seealso{ellipses2d, drawCircle, drawEllipseArc, ellipseAsPolygon}
%% @end deftypefn

function varargout = drawEllipse(varargin)

  % extract dawing style strings
  styles = {};
  for i = 1:length(varargin)
      if ischar(varargin{i})
          styles = varargin(i:end);
          varargin(i:end) = [];
          break;
      end
  end

  % extract ellipse parameters
  if length(varargin)==1
      % ellipse is given in a single array
      ellipse = varargin{1};
      x0 = ellipse(:, 1);
      y0 = ellipse(:, 2);
      a  = ellipse(:, 3);
      b  = ellipse(:, 4);
      if length(ellipse)>4
          theta = ellipse(:, 5);
      else
          theta = zeros(size(x0));
      end
      
  elseif length(varargin)>=4
      % ellipse parameters given as separate arrays
      x0 = varargin{1};
      y0 = varargin{2};
      a  = varargin{3};
      b  = varargin{4};
      if length(varargin)>4
          theta = varargin{5};
      else
          theta = zeros(size(x0));
      end
      
  else
      error('drawEllipse: incorrect input arguments');
  end


  %% Process drawing of a set of ellipses

  % angular positions of vertices
  t = linspace(0, 2*pi, 145);

  % compute position of points to draw each ellipse
  h = zeros(length(x0), 1);
  for i = 1:length(x0)
      % pre-compute rotation angles (given in degrees)
      cot = cosd(theta(i));
      sit = sind(theta(i));
      
      % compute position of points used to draw current ellipse
      xt = x0(i) + a(i) * cos(t) * cot - b(i) * sin(t) * sit;
      yt = y0(i) + a(i) * cos(t) * sit + b(i) * sin(t) * cot;
      
      % stores handle to graphic object
      h(i) = plot(xt, yt, styles{:});
  end

  % return handles if required
  if nargout > 0
      varargout = {h};
  end

endfunction

