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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 varargout = clipPolygonByLine(poly, line, varargin)
%CLIPPOLYGONBYLINE Clip a polygon by a directed line.
%
% POLY2 = clipPolygonByLine(POLY, LINE)
% POLY is a [Nx2] array of points, and LINE is given as [x0 y0 dx dy].
% The result POLY2:
% - Represents the part of the polygon on the left side of the directed
% line, the left half-plane, if the line intersects the polygon.
% - Is the same as POLY if the polygon is on the left side of the
% directed line and the line does not intersect the polygon.
% - Is an empty polygon [0x2] if the polygon on the right side of the
% directed line and the line does not intersect the polygon.
%
% [POLY_L, POLY_R] = clipPolygonByLine(POLY, LINE, 'method', 'polyshape')
% Uses MATLAB polyshape objects and functions to clip the polygon by the
% line. Returns the right part POLY_R (right half-plane) in addition to
% the left part POLY_L (left half-plane) in the polygon cell format.
%
% Example
% line = [0.4 0 1 1];
% r = [2.5, 2, 1];
% poly = flipud(circleToPolygon([0 0 r(1)], round(2*pi*r(1))));
% poly2 = clipPolygonByLine(poly, line);
% figure('color','w','numbertitle','off','name','Method: legland')
% axis equal tight; hold on; xlabel('x'); ylabel('y')
% fillPolygon(poly2)
% poly2_centroid = polygonCentroid(poly2);
% drawLabels(poly2_centroid,'L ','HorizontalAlignment','Right')
% scatter(poly2_centroid(1), poly2_centroid(2),[],'k','filled')
% midCircle = circleToPolygon([0 0 r(2)], round(2*pi*r(2)));
% innerCircle = flipud(circleToPolygon([0 0 r(3)], round(2*pi*r(3))));
% poly = {poly, midCircle, innerCircle};
% clipPolygonByLine(poly, line, 'method','polyshape','debug',1);
%
% See also
% clipPolygon
% ------
% Author: David Legland, oqilipo
% E-mail: david.legland@inrae.fr
% Created: 2005-07-31
% Copyright 2005-2023 INRA - Cepia Software Platform
% Parsing
p = inputParser;
logParValidFunc=@(x) (islogical(x) || isequal(x,1) || isequal(x,0));
addParameter(p,'method','legland',@(x) any(validatestring(x,{'legland','polyshape'})));
addParameter(p,'debugVisu',false,logParValidFunc);
parse(p,varargin{:});
method = p.Results.method;
debugVisu = p.Results.debugVisu;
if iscell(poly) && numel(poly)==1
poly = poly{1};
elseif iscell(poly) && length(poly) > 1
method = 'polyshape';
end
if ~iscell(poly) && any(isnan(poly(:)))
poly = splitPolygons(poly);
method = 'polyshape';
end
switch method
case 'legland'
% avoid to process empty polygons
if size(poly, 1)<3
varargout{1} = zeros([0 2]);
return;
end
% ensure the last point is the same as the first one
if sum(poly(end, :)==poly(1,:))~=2
poly = [poly; poly(1,:)];
end
N = size(poly, 1);
edges = [poly([N 1:N-1], :) poly];
b = isLeftOriented(poly, line);
% case of totally clipped polygon
if sum(b)==0
varargout{1} = zeros(0, 2);
return;
end
poly2 = zeros(0, 2);
i=1;
while i<=N
if isLeftOriented(poly(i,:), line)
% keep all points located on the right side of line
poly2 = [poly2; poly(i,:)]; %#ok<AGROW>
else
% compute of preceeding edge with line
if i>1
poly2 = [poly2; intersectLineEdge(line, edges(i, :))]; %#ok<AGROW>
end
% go to the next point on the left side
i=i+1;
while i<=N
% find the next point on the right side
if isLeftOriented(poly(i,:), line)
% add intersection of previous edge
poly2 = [poly2; intersectLineEdge(line, edges(i, :))]; %#ok<AGROW>
% add current point
poly2 = [poly2; poly(i,:)]; %#ok<AGROW>
% exit the second loop
break;
end
i=i+1;
end
end
i=i+1;
end
% remove last point if it is the same as the first one
if sum(poly2(end, :)==poly(1,:))==2
poly2 = poly2(1:end-1, :);
end
if debugVisu
figure('color','w','numbertitle','off', ...
'name', ['Debug Figure: ' mfilename ...
'.m, Method: ' method]);
axis equal tight; hold on; xlabel('x'); ylabel('y')
fillPolygon(poly2,'g')
poly2_centroid = polygonCentroid(poly2);
drawLabels(poly2_centroid,'L ','HorizontalAlignment','Right')
scatter(poly2_centroid(1), poly2_centroid(2),[],'k','filled')
end
varargout{1} = poly2;
case 'polyshape'
warning('off','MATLAB:polyshape:repairedBySimplify')
polyShape = polygonToPolyshape(poly, 'debugVisu',0);
warning('on','MATLAB:polyshape:repairedBySimplify')
[bblim(1:2), bblim(3:4)] = boundingbox(polyShape);
bbXdist = bblim(2)-bblim(1);
bbYdist = bblim(4)-bblim(3);
% Increase the bounding box a little bit
bblim(1) = bblim(1)-0.01*bbXdist;
bblim(2) = bblim(2)+0.01*bbXdist;
bblim(3) = bblim(3)-0.01*bbYdist;
bblim(4) = bblim(4)+0.01*bbYdist;
% Bounding box
BB = [bblim(1) bblim(3); bblim(2) bblim(3); ...
bblim(2) bblim(4); bblim(1) bblim(4)];
% Clip the bounding box by the line
BB_L = clipPolygonByLine(BB, line);
PS_R = subtract(polyShape, polyshape(BB_L));
lineRev = [line(1:2) -line(3:4)];
BB_R = clipPolygonByLine(BB, lineRev);
PS_L = subtract(polyShape, polyshape(BB_R));
lineSeg = clipLine(line, bblim);
lineSeg = [lineSeg(1:2); lineSeg(3:4)];
% Intersection edges
itsEdges = intersect(polyShape,lineSeg);
itsEdges(2:end+1, 3:4) = itsEdges;
itsEdges(1,3:4) = nan;
itsEdges(end,1:2) = nan;
itsEdges(any(isnan(itsEdges),2),:) = [];
if debugVisu
figure('color','w','numbertitle','off', ...
'name', ['Debug Figure: ' mfilename ...
'.m, Method: ' method]);
axis equal tight; hold on; xlabel('x'); ylabel('y')
plot(PS_R,'FaceColor','g','EdgeColor','k')
plot(PS_L,'FaceColor','b','EdgeColor','k')
[PS_R_centroid(1), PS_R_centroid(2)] = centroid(PS_R);
drawLabels(PS_R_centroid,' R','HorizontalAlignment','Left')
scatter(PS_R_centroid(1), PS_R_centroid(2),[],'g','filled')
[PS_L_centroid(1), PS_L_centroid(2)] = centroid(PS_L);
drawLabels(PS_L_centroid,'L ','HorizontalAlignment','Right')
scatter(PS_L_centroid(1), PS_L_centroid(2),[],'b','filled')
drawEdge(itsEdges,'LineStyle','-','LineWidth',2,'Color','k')
end
varargout{1} = splitPolygons(PS_L.Vertices);
varargout{2} = splitPolygons(PS_R.Vertices);
varargout{3} = itsEdges;
end
end
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