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## Copyright (C) 2004-2011 David Legland <david.legland@grignon.inra.fr>
## Copyright (C) 2004-2011 INRA - CEPIA Nantes - MIAJ (Jouy-en-Josas)
## Copyright (C) 2012 Adapted to Octave by Juan Pablo Carbajal <carbajal@ifi.uzh.ch>
## All rights reserved.
##
## 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 AUTHOR 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.
## -*- 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);