%% 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{edge} = } createEdge (@var{p1}, @var{p2})
%% @deftypefnx {Function File} {@var{edge} = } createEdge (@var{x0}, @var{y0}, @var{dx}, @var{dy})
%% @deftypefnx {Function File} {@var{edge} = } createEdge (@var{param})
%% @deftypefnx {Function File} {@var{edge} = } createEdge (@var{line}, @var{d})
%% Create an edge between two points, or from a line.
%%
%%   The internal format for edge representation is given by coordinates of
%%   two points : [x1 y1 x2 y2].
%%   This function can serve as a line to edge converter.
%%
%%
%%   Returns the edge between the two given points @var{p1} and @var{p2}.
%%   
%%   Returns the edge going through point (@var{x0}, @var{y0}) and with direction
%%   vector (@var{dx},@var{dy}).
%%
%%   When @var{param} is an array of 4 values, creates the edge going through the
%%   point (param(1) param(2)), and with direction vector given by
%%   (param(3) param(4)).
%%   
%% When @var{line} is given, creates the edge contained in @var{line}, with same
%% direction and start point, but with length given by @var{d}.
%%
%%
%%   Note: in all cases, parameters can be vertical arrays of the same
%%   dimension. The result is then an array of edges, of dimensions [N*4].
%%
%% @seealso{edges2d, lines2d, drawEdge, clipEdge}
%% @end deftypefn

function edge = createEdge(varargin)

  if length(varargin)==1
      % Only one input parameter. It can be :
      % - line angle
      % - array of four parameters
      % TODO : add control for arrays of lines.
      var = varargin{1};
      
      if size(var, 2)==4
          % 4 parameters of the line in a single array.
          %edge = var;
          edge = zeros(size(var));
          edge(:, 1:2) = var(:,1:2);
          edge(:, 3:4) = edge(:, 1:2)+var(:,3:4);
      elseif size(var, 2)==1
          % 1 parameter : angle of the line, going through origin.
          edge = [zeros(size(var,1)) zeros(size(var,1)) cos(var) sin(var)];
      else
          error('wrong number of dimension for arg1 : can be 1 or 4');
      end
      
  elseif length(varargin)==2    
      % 2 input parameters. They can be :
      % - 2 points, then 2 arrays of 1*2 double,
      % - a line, and a distance.
      v1 = varargin{1};
      v2 = varargin{2};
      if size(v1, 2)==2
          % first input parameter is first point, and second input is the
          % second point.
          %edge = [v1(:,1), v1(:,2), v2(:,1), v2(:,2)];
          edge = [v1 v2];
      else
          % first input parameter is a line, and second one a distance.
          angle = atan2(v1(:,4), v1(:,3));
          edge = [v1(:,1), v1(:,2), v1(:,1)+v2.*cos(angle), v1(:,2)+v2.*sin(angle)];
      end
      
  elseif length(varargin)==3
      % 3 input parameters :
      % first one is a point belonging to the line,
      % second and third ones are direction vector of the line (dx and dy).
      p = varargin{1};
      edge = [p(:,1) p(:,2) p(:,1)+varargin{2} p(:,2)+varargin{3}];
     
  elseif length(varargin)==4
      % 4 input parameters :
      % they are x0, y0 (point belonging to line) and dx, dy (direction
      % vector of the line).
      % All parameters should have the same size.
      edge = [varargin{1} varargin{2} varargin{1}+varargin{3} varargin{2}+varargin{4}];
  else
      error('Wrong number of arguments in ''createLine'' ');
  end

endfunction
