medianLine

MEDIANLINE Create a median line between two points.

   L = medianLine(P1, P2);
   Create the median line of points P1 and P2, that is the line containing
   all points located at equal distance of P1 and P2.

   L = medianLine(PTS);
   Creates the median line of 2 points, given as a 2*2 array. Array has
   the form:
   [ [ x1 y1 ] ; [ x2 y2 ] ]

   L = medianLine(EDGE);
   Creates the median of the edge. Edge is a 1*4 array, containing [X1 Y1]
   coordinates of first point, and [X2 Y2], the coordinates of the second
   point.
  
   Example
   % Draw the median line of two points
     P1 = [10 20];
     P2 = [30 50];
     med = medianLine(P1, P2);
     figure; axis square; axis([0 100 0 100]);
     drawEdge([P1 P2], 'linewidth', 2, 'color', 'k');
     drawLine(med)

   % Draw the median line of an edge
     P1 = [50 60];
     P2 = [80 30];
     edge = createEdge(P1, P2);
     figure; axis square; axis([0 100 0 100]);
     drawEdge(edge, 'linewidth', 2)
     med = medianLine(edge);
     drawLine(med)


   See also:
   lines2d, createLine, orthogonalLine

   ---------
   author : David Legland
   INRA - TPV URPOI - BIA IMASTE
   created the 31/10/2003.

0001 function line = medianLine(varargin)
0002 %MEDIANLINE Create a median line between two points.
0003 %
0004 %   L = medianLine(P1, P2);
0005 %   Create the median line of points P1 and P2, that is the line containing
0006 %   all points located at equal distance of P1 and P2.
0007 %
0008 %   L = medianLine(PTS);
0009 %   Creates the median line of 2 points, given as a 2*2 array. Array has
0010 %   the form:
0011 %   [ [ x1 y1 ] ; [ x2 y2 ] ]
0012 %
0013 %   L = medianLine(EDGE);
0014 %   Creates the median of the edge. Edge is a 1*4 array, containing [X1 Y1]
0015 %   coordinates of first point, and [X2 Y2], the coordinates of the second
0016 %   point.
0017 %
0018 %   Example
0019 %   % Draw the median line of two points
0020 %     P1 = [10 20];
0021 %     P2 = [30 50];
0022 %     med = medianLine(P1, P2);
0023 %     figure; axis square; axis([0 100 0 100]);
0024 %     drawEdge([P1 P2], 'linewidth', 2, 'color', 'k');
0025 %     drawLine(med)
0026 %
0027 %   % Draw the median line of an edge
0028 %     P1 = [50 60];
0029 %     P2 = [80 30];
0030 %     edge = createEdge(P1, P2);
0031 %     figure; axis square; axis([0 100 0 100]);
0032 %     drawEdge(edge, 'linewidth', 2)
0033 %     med = medianLine(edge);
0034 %     drawLine(med)
0035 %
0036 %
0037 %   See also:
0038 %   lines2d, createLine, orthogonalLine
0039 %
0040 %   ---------
0041 %   author : David Legland
0042 %   INRA - TPV URPOI - BIA IMASTE
0043 %   created the 31/10/2003.
0044 %
0045 
0046 % history
0047 % 2010-08-06 vectorize and change behaviour for N-by-4 inputs
0048 
0049 nargs = length(varargin);
0050 
0051 if nargs == 1
0052     tab = varargin{1};
0053     if size(tab, 2)==2
0054         % input is an array of two points
0055         x0 = tab(1,1); 
0056         y0 = tab(1,2);
0057         dx = tab(2,1)-x0; 
0058         dy = tab(2,2)-y0;
0059     else
0060         % input is an edge
0061         x0 = tab(:, 1); 
0062         y0 = tab(:, 2);
0063         dx = tab(:, 3) - tab(:, 1); 
0064         dy = tab(:, 4) - tab(:, 2);
0065     end
0066     
0067 elseif nargs==2
0068     % input is given as two points, or two point arrays
0069     p1 = varargin{1};
0070     p2 = varargin{2};
0071     x0 = p1(:, 1); 
0072     y0 = p1(:, 2);
0073     dx = bsxfun(@minus, p2(:, 1), x0); 
0074     dy = bsxfun(@minus, p2(:, 2), y0);
0075     
0076 else
0077     error('Too many input arguments');
0078 end
0079 
0080 % compute median using middle point of the edge, and the direction vector
0081 % rotated by 90 degrees counter-clockwise
0082 line = [bsxfun(@plus, x0, dx/2), bsxfun(@plus, y0, dy/2), -dy, dx];