transformPoint

 Apply an affine transform to a point or a point set.

   PT2 = transformPoint(PT1, TRANSFO);
   Returns the result of the transformation TRANSFO applied to the point
   PT1. PT1 has the form [xp yp], and TRANSFO is either a 2-by-2, a
   2-by-3, or a 3-by-3 matrix, 

   Format of TRANSFO can be one of :
   [a b]   ,   [a b c] , or [a b c]
   [d e]       [d e f]      [d e f]
                            [0 0 1]

   PT2 = transformPoint(PT1, TRANSFO);
   Also works when PTA is a N-by-2 array representing point coordinates.
   In this case, the result PT2 has the same size as PT1.

   [X2, Y2] = transformPoint(X1, Y1, TRANS);
   Also works when PX1 and PY1 are two arrays the same size. The function
   transforms each pair (PX1, PY1), and returns the result in (X2, Y2),
   which has the same size as (PX1 PY1). 


   See also:
     points2d, transforms2d, translation, rotation

0001 function varargout = transformPoint(varargin)
0002 % Apply an affine transform to a point or a point set.
0003 %
0004 %   PT2 = transformPoint(PT1, TRANSFO);
0005 %   Returns the result of the transformation TRANSFO applied to the point
0006 %   PT1. PT1 has the form [xp yp], and TRANSFO is either a 2-by-2, a
0007 %   2-by-3, or a 3-by-3 matrix,
0008 %
0009 %   Format of TRANSFO can be one of :
0010 %   [a b]   ,   [a b c] , or [a b c]
0011 %   [d e]       [d e f]      [d e f]
0012 %                            [0 0 1]
0013 %
0014 %   PT2 = transformPoint(PT1, TRANSFO);
0015 %   Also works when PTA is a N-by-2 array representing point coordinates.
0016 %   In this case, the result PT2 has the same size as PT1.
0017 %
0018 %   [X2, Y2] = transformPoint(X1, Y1, TRANS);
0019 %   Also works when PX1 and PY1 are two arrays the same size. The function
0020 %   transforms each pair (PX1, PY1), and returns the result in (X2, Y2),
0021 %   which has the same size as (PX1 PY1).
0022 %
0023 %
0024 %   See also:
0025 %     points2d, transforms2d, translation, rotation
0026 %
0027 
0028 %   ---------
0029 %   author : David Legland
0030 %   INRA - TPV URPOI - BIA IMASTE
0031 %   created the 06/04/2004.
0032 %
0033 
0034 %   HISTORY
0035 %   25/04/2005 : support for 2D arrays of points (px, py, trans).
0036 
0037 % parse input arguments
0038 if length(varargin) == 2
0039     var = varargin{1};
0040     px = var(:,1);
0041     py = var(:,2);
0042     trans = varargin{2};
0043 elseif length(varargin) == 3
0044     px = varargin{1};
0045     py = varargin{2};
0046     trans = varargin{3};
0047 else
0048     error('wrong number of arguments in "transformPoint"');
0049 end
0050 
0051 
0052 % apply linear part of the transform
0053 px2 = px * trans(1,1) + py * trans(1,2);
0054 py2 = px * trans(2,1) + py * trans(2,2);
0055 
0056 % add translation vector, if exist
0057 if size(trans, 2) > 2
0058     px2 = px2 + trans(1,3);
0059     py2 = py2 + trans(2,3);
0060 end
0061 
0062 % format output arguments
0063 if nargout < 2
0064     varargout{1} = [px2 py2];
0065 elseif nargout
0066     varargout{1} = px2;
0067     varargout{2} = py2;
0068 end