%% Copyright (c) 2011, INRA
%% 2004-2011, David Legland <david.legland@grignon.inra.fr>
%% 2011 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
%%
%% All rights reserved.
%% (simplified BSD License)
%%
%% Redistribution and use in source and binary forms, with or without
%% modification, are permitted provided that the following conditions are met:
%%
%% 1. Redistributions of source code must retain the above copyright notice, this
%%    list of conditions and the following disclaimer.
%%     
%% 2. Redistributions in binary form must reproduce the above copyright notice, 
%%    this list of conditions and the following disclaimer in the documentation
%%    and/or other materials provided with the distribution.
%%
%% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
%% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
%% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
%% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
%% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
%% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
%% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
%% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
%% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
%% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
%% POSSIBILITY OF SUCH DAMAGE.
%%
%% The views and conclusions contained in the software and documentation are
%% those of the authors and should not be interpreted as representing official
%% policies, either expressed or implied, of copyright holder.

%% -*- texinfo -*-
%% @deftypefn {Function File} {@var{T} = } createScaling (@var{s})
%% @deftypefnx {Function File} {@var{T} = } createScaling (@var{sx}, @var{sy})
%% Create the 3x3 matrix of a scaling in 2 dimensions.
%
%   Assume scaling @var{s} is equal n all directions unless @var{sx} and @var{sy} are given.
%   Returns the matrix corresponding to scaling in the 2 main directions.
%   The returned matrix has the form:
%   [SX  0  0]
%   [0  SY  0]
%   [0   0  1]
%
%   @seealso{transforms2d, transformPoint, createTranslation, createRotation}
%% @end deftypefn

function trans = createScaling(varargin)

  % defined default arguments
  sx = 1;
  sy = 1;
  cx = 0;
  cy = 0;

  % process input arguments
  if length(varargin)==1
      % the argument is either the scaling factor in both direction,
      % or a 1x2 array containing scaling factor in each direction
      var = varargin{1};
      sx = var(1);
      sy = var(1);
      if length(var)>1
          sy = var(2);
      end
  elseif length(varargin)==2
      % the 2 arguments are the scaling factors in each dimension
      sx = varargin{1};
      sy = varargin{2};
  elseif length(varargin)==3
      % first argument is center, 2nd and 3d are scaling factors
      center = varargin{1};
      cx = center(1);
      cy = center(2);
      sx = varargin{2};
      sy = varargin{3};
  end

  % create result matrix
  trans = [sx 0 cx*(1-sx); 0 sy cy*(1-sy); 0 0 1];

endfunction

%!test
%!  trans = createScaling(2);
%!  assert (trans, [2 0 0;0 2 0;0 0 1], 1e-6);

%!test
%!  trans = createScaling(2, 3);
%!  assert (trans, [2 0 0;0 3 0;0 0 1], 1e-6);

%!test
%!  trans = createScaling([2 3]);
%!  assert (trans, [2 0 0;0 3 0;0 0 1], 1e-6);

%!test
%!  sx = 2;
%!  sy = 3;
%!  p0 = [4 5];
%!  trans1 = createScaling(p0, sx, sy);
%!  t1 = createTranslation(-p0);
%!  sca = createScaling(sx, sy);
%!  t2 = createTranslation(p0);
%!  trans2 = t2*sca*t1;
%!  assert (trans1, trans2, 1e-6);
