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## Copyright (C) 2024 David Legland
## 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.
##
## 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 the copyright holders.
function edge = clipLine(line, box, varargin)
%CLIPLINE Clip a line with a box.
%
% EDGE = clipLine(LINE, BOX);
% 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,
% 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 LINE is a N-by-4 array, if BOX is a Nx4 array,
% or if both LINE and BOX are N-by-4 arrays. In these cases, EDGE is a
% N-by-4 array.
%
%
% Example
% line = [30 40 10 0];
% box = [0 100 0 100];
% res = clipLine(line, box)
% res =
% 0 40 100 40
%
% See also
% lines2d, boxes2d, edges2d
% clipEdge, clipRay, clipLine3d
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2007-08-27, using Matlab 7.4.0.287 (R2007a)
% Copyright 2007-2023 INRA - Cepia Software Platform
% adjust size of two input arguments
nLines = size(line, 1);
nBoxes = size(box, 1);
if nLines == 1 && nBoxes > 1
line = repmat(line, nBoxes, 1);
elseif nBoxes == 1 && nLines > 1
box = repmat(box, nLines, 1);
elseif nLines ~= nBoxes
error('bad sizes for input');
end
% allocate memory
nLines = size(line, 1);
edge = zeros(nLines, 4);
% main loop on lines
for i = 1:nLines
% extract limits of the box
xmin = box(i, 1);
xmax = box(i, 2);
ymin = box(i, 3);
ymax = box(i, 4);
% use direction vector for box edges similar to direction vector of the
% line in order to reduce computation errors
delta = hypot(line(i,3), line(i,4));
% compute intersection with each edge of the box
px1 = intersectLines(line(i,:), [xmin ymin delta 0]); % lower edge
px2 = intersectLines(line(i,:), [xmax ymin 0 delta]); % right edge
py1 = intersectLines(line(i,:), [xmax ymax -delta 0]); % upper edge
py2 = intersectLines(line(i,:), [xmin ymax 0 -delta]); % left edge
% 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, line(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
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