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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 poly2 = clipPolygon(polygon, w)
%CLIPPOLYGON Clip a polygon with a rectangular box.
%
% POLY2 = clipPolygon(POLY, BOX);
% POLY is N-by-2 array of points
% BOX has the form: [XMIN XMAX YMIN YMAX].
% Returns the polygon created by the intersection of the polygon POLY and
% the bounding box BOX.
%
% Note: Works only for convex polygons at the moment.
%
% See also
% polygons2d, boxes2d, clipPolygonByLine, clipPolyline
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2005-05-14
% Copyright 2005-2023 INRA - Cepia Software Platform
% check case of polygons stored in cell array
if iscell(polygon)
poly2 = cell(1, length(polygon));
for i = 1:length(polygon)
poly2{i} = clipPolygon(polygon{i}, w);
end
return;
end
% check case of empty polygon
N = size(polygon, 1);
if N == 0
poly2 = zeros(0, 2);
return
end
% create edges array of polygon
edges = [polygon polygon([2:N 1], :)];
% clip edges
edges = clipEdge(edges, w);
% select non empty edges, and get their vertices
ind = sum(abs(edges), 2) > 1e-14;
pts = unique([edges(ind, 1:2); edges(ind, 3:4)], 'rows');
% add vertices of window corner
corners = [w(1) w(3); w(1) w(4);w(2) w(3);w(2) w(4)];
ind = inpolygon(corners(:,1), corners(:,2), polygon(:,1), polygon(:,2));
pts = [pts; corners(ind, :)];
% polygon totally outside the window
if size(pts, 1)==0
poly2 = pts;
return;
end
% compute centroid of visible polygon
pc = centroid(pts);
% sort vertices around polygon
angle = edgeAngle([repmat(pc, [size(pts, 1) 1]) pts]);
[dummy, I] = sort(angle); %#ok<ASGLU>
% create resulting polygon
poly2 = pts(I, :);
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