%% 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{line} =} createLine(varargin)
%% Create a straight line from 2 points, or from other inputs
%%
%%   Line is represented in a parametric form : [x0 y0 dx dy]
%%   x = x0 + t*dx
%%   y = y0 + t*dy;
%%
%%
%%   L = createLine(p1, p2);
%%   Returns the line going through the two given points.
%%   
%%   L = createLine(x0, y0, dx, dy);
%%   Returns the line going through point (x0, y0) and with direction
%%   vector(dx, dy).
%%
%%   L = createLine(LINE);
%%   where LINE is an array of 4 values, creates the line going through the
%%   point (LINE(1) LINE(2)), and with direction given by vector (LINE(3)
%%   LINE(4)). 
%%   
%%   L = createLine(THETA);
%%   Create a polar line originated at (0,0) and with angle THETA.
%%
%%   L = createLine(RHO, THETA);
%%   Create a polar line with normal theta, and with min distance to origin
%%   equal to rho. rho can be negative, in this case, the line is the same
%%   as with CREATELINE(-rho, theta+pi), but the orientation is different.
%%
%%
%%   Note: in all cases, parameters can be vertical arrays of the same
%%   dimension. The result is then an array of lines, of dimensions [N*4].
%%
%%   NOTE : A line can also be represented with a 1*5 array : 
%%   [x0 y0 dx dy t].
%%   whith 't' being one of the following : 
%%   - t=0 : line is a singleton (x0,y0)
%%   - t=1 : line is an edge segment, between points (x0,y0) and (x0+dx,
%%   y0+dy).
%%   - t=Inf : line is a Ray, originated from (x0,y0) and going to infinity
%%   in the direction(dx,dy).
%%   - t=-Inf : line is a Ray, originated from (x0,y0) and going to infinity
%%   in the direction(-dx,-dy).
%%   - t=NaN : line is a real straight line, and contains all points
%%   verifying the above equation.
%%   This seems us a convenient way to represent uniformly all kind of lines
%%   (including edges, rays, and even point).
%%
%%   NOTE2 : Any line object can be represented using a 1x6 array :
%%   [x0 y0 dx dy t0 t1]
%%   the first 4 parameters define the supporting line,
%%   t0 represent the position of the first point on the line, 
%%   and t1 the position of the last point.
%%   * for edges : t0 = 0, and t1=1
%%   * for straight lines : t0 = -inf, t1=inf
%%   * for rays : t0=0, t1=inf (or t0=-inf,t1=0 for inverted ray).
%%   I propose to call these objects 'lineArc'
%%
%% @seealso{lines2d, createEdge, createRay}
%% @end deftypefn

function line = createLine(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.
          line = var;
      elseif size(var, 2)==1
          % 1 parameter : angle of the line, going through origin.
          line = [zeros(size(var)) zeros(size(var)) 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 :
      % - line angle and signed distance to origin.
      % - 2 points, then 2 arrays of 1*2 double.
      v1 = varargin{1};
      v2 = varargin{2};
      if size(v1, 2)==1
          % first param is angle of line, and second param is signed distance
          % to origin.
          line = [v1.*cos(v2) v1.*sin(v2) -sin(v2) cos(v2)];
      else
          % first input parameter is first point, and second input is the
          % second point.
          line = [v1(:,1), v1(:,2), v2(:,1)-v1(:,1), v2(:,2)-v1(:,2)];    
      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};
      line = [p(:,1) p(:,2) varargin{2} varargin{3}];
     
  elseif length(varargin)==4
      % 4 input parameters :
      % they are x0, y0 (point belongng to line) and dx, dy (direction vector
      % of the line).
      % All parameters should have the same size.
      line = [varargin{1} varargin{2} varargin{3} varargin{4}];
  else
      error('Wrong number of arguments in ''createLine'' ');
  end

endfunction

%!test
%! p1 = [1 1];
%! p2 = [2 3];
%! lin = createLine(p1, p2);
%! assert (p1, lin(1,1:2), 1e-6);
%! assert (p2-p1, lin(1,3:4), 1e-6);

%!test
%! p1 = [1 1;1 1];
%! p2 = [2 3;2 4];
%! lin = createLine(p1, p2);
%! assert (2, size(lin, 1));
%! assert (p1, lin(:,1:2), 1e-6);
%! assert (p2-p1, lin(:,3:4), 1e-6);

