--- /dev/null
+%% Copyright (c) 2011, INRA
+%% 2007-2011, 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{edge} =} clipLine (@var{line}, @var{box})
+%% Clip a line with a box.
+%%
+%% @var{line} is a straight line given as a 4 element row vector: [x0 y0 dx dy],
+%% with (x0 y0) being a point of the line and (dx dy) a direction vector,
+%% @var{box} is the clipping box, given by its extreme coordinates:
+%% [xmin xmax ymin ymax].
+%% The result is given as an edge, defined by the coordinates of its 2
+%% extreme points: [x1 y1 x2 y2].
+%% If line does not intersect the box, [NaN NaN NaN NaN] is returned.
+%%
+%% Function works also if @var{line} is a Nx4 array, if @var{box} is a Nx4 array, or
+%% if both @var{line} and @var{box} are Nx4 arrays. In these cases, @var{edge} is a Nx4
+%% array.
+%%
+%% Example:
+%%
+%% @example
+%% line = [30 40 10 0];
+%% box = [0 100 0 100];
+%% res = clipLine(line, box)
+%% res =
+%% 0 40 100 40
+%% @end example
+%%
+%% @seealso{lines2d, boxes2d, edges2d, clipEdge, clipRay}
+%% @end deftypefn
+
+function edge = clipLine(lin, bb, varargin)
+
+ % adjust size of two input arguments
+ if size(lin, 1)==1
+ lin = repmat(lin, size(bb, 1), 1);
+ elseif size(bb, 1)==1
+ bb = repmat(bb, size(lin, 1), 1);
+ elseif size(lin, 1) ~= size(bb, 1)
+ error('bad sizes for input');
+ end
+
+ % allocate memory
+ nbLines = size(lin, 1);
+ edge = zeros(nbLines, 4);
+
+ % main loop on lines
+ for i=1:nbLines
+ % extract limits of the box
+ xmin = bb(i, 1);
+ xmax = bb(i, 2);
+ ymin = bb(i, 3);
+ ymax = bb(i, 4);
+
+ % use direction vector for box edges similar to direction vector of the
+ % line in order to reduce computation errors
+ delta = hypot(lin(i,3), lin(i,4));
+
+
+ % compute intersection with each edge of the box
+
+ % lower edge
+ px1 = intersectLines(lin(i,:), [xmin ymin delta 0]);
+ % right edge
+ px2 = intersectLines(lin(i,:), [xmax ymin 0 delta]);
+ % upper edge
+ py1 = intersectLines(lin(i,:), [xmax ymax -delta 0]);
+ % left edge
+ py2 = intersectLines(lin(i,:), [xmin ymax 0 -delta]);
+
+ % remove undefined intersections (case of lines parallel to box edges)
+ points = [px1 ; px2 ; py1 ; py2];
+ points = points(isfinite(points(:,1)), :);
+
+ % sort points according to their position on the line
+ pos = linePosition(points, lin(i,:));
+ [pos inds] = sort(pos); %#ok<ASGLU>
+ points = points(inds, :);
+
+ % create clipped edge by using the two points in the middle
+ ind = size(points, 1)/2;
+ inter1 = points(ind,:);
+ inter2 = points(ind+1,:);
+ edge(i, 1:4) = [inter1 inter2];
+
+ % check that middle point of the edge is contained in the box
+ midX = mean(edge(i, [1 3]));
+ xOk = xmin <= midX && midX <= xmax;
+ midY = mean(edge(i, [2 4]));
+ yOk = ymin <= midY && midY <= ymax;
+
+ % if one of the bounding condition is not met, set edge to NaN
+ if ~(xOk && yOk)
+ edge (i,:) = NaN;
+ end
+ end
+endfunction
+
+%!demo
+%! lin = [30 40 10 0];
+%! bb = [0 100 0 100];
+%! res = clipLine(lin, bb)
+%!
+%! drawBox(bb,'color','k');
+%! line(lin([1 3]),lin([2 4]),'color','b');
+%! line(res([1 3]),res([2 4]),'color','r','linewidth',2);
+%! axis tight
+%! v = axis ();
+%! axis(v+[0 10 -10 0])
+
+%!test % inside, to the right % inside, to the left% outside
+%! bb = [0 100 0 100];
+%! lin = [30 40 10 0];
+%! edge = [0 40 100 40];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [30 40 -10 0];
+%! edge = [100 40 0 40];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [30 140 10 0];
+%! assert (sum(isnan(clipLine(lin, bb)))==4);
+
+%!test % inside, upward % inside, downward % outside
+%! bb = [0 100 0 100];
+%! lin = [30 40 0 10];
+%! edge = [30 0 30 100];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [30 40 0 -10];
+%! edge = [30 100 30 0];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [140 30 0 10];
+%! assert (sum(isnan(clipLine(lin, bb)))==4);
+
+%!test % inside, top right corner% inside, down right corner % outside
+%! bb = [0 100 0 100];
+%! lin = [80 30 10 10];
+%! edge = [50 0 100 50];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [20 70 10 10];
+%! edge = [0 50 50 100];
+%! assert (edge, clipLine(lin, bb), 1e-6);
+%! lin = [140 -30 10 10];
+%! assert (sum(isnan(clipLine(lin, bb)))==4);
+%! lin = [-40 130 10 10];
+%! assert (sum(isnan(clipLine(lin, bb)))==4);
+
+%!test %multilines % inside, top right corner
+%! bb = [0 100 0 100];
+%! lin = [...
+%! 80 30 10 10; ...
+%! 20 70 10 10; ...
+%! 140 -30 10 10; ...
+%! -40 130 10 10];
+%! edge = [...
+%! 50 0 100 50; ...
+%! 0 50 50 100; ...
+%! NaN NaN NaN NaN; ...
+%! NaN NaN NaN NaN; ...
+%! ];
+%! clipped = clipLine(lin, bb);
+%! assert (4, size(clipped, 1));
+%! assert (edge(1:2, :), clipped(1:2, :), 1e-6);
+%! assert (sum(isnan(clipped(3,:)))==4);
+%! assert (sum(isnan(clipped(4,:)))==4);
+
+%!test % test clipping of horizontal lines % inside, to the right
+%! bb = [-1 1 -1 1]*1e10;
+%! lin = [3 0 1 2];
+%! D = 1e10;
+%! edge = [3-D/2 -D 3+D/2 D];
+%! clipped = clipLine(lin, bb);
+%! assert (edge, clipped);
+
+%!test % inside, to the right
+%! bb = [-1 1 -1 1]*100;
+%! lin = [3 0 1*1e10 2*1e10];
+%! D = 100;
+%! edge = [3-D/2 -D 3+D/2 D];
+%! clipped = clipLine(lin, bb);
+%! assert (edge, clipped, 1e-6);
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