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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 = graph2Contours(nodes, edges) %#ok<INUSL>
%GRAPH2CONTOURS Convert a graph to a set of contour curves.
%
% CONTOURS = GRAPH2CONTOURS(NODES, EDGES)
% NODES, EDGES is a graph representation (type "help graphs" for details)
% The algorithm assume every node has degree 2, and the set of edges
% forms only closed loops. The result is a list of indices arrays, each
% array containing consecutive point indices of a contour.
%
% To transform contours into drawable curves, please use :
% CURVES{i} = NODES(CONTOURS{i}, :);
%
%
% NOTE : contours are not oriented. To manage contour orientation, edges
% also need to be oriented. So we must precise generation of edges.
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2004-08-05
% Copyright 2004-2023 INRA - TPV URPOI - BIA IMASTE
curves = {};
c = 0;
while size(edges,1)>0
% find first point of the curve
n0 = edges(1,1);
curve = n0;
% second point of the curve
n = edges(1,2);
e = 1;
while true
% add current point to the curve
curve = [curve n]; %#ok<AGROW>
% remove current edge from the list
edges = edges((1:size(edges,1))~=e,:);
% find index of edge containing reference to current node
e = find(edges(:,1)==n | edges(:,2)==n);
e = e(1);
% get index of next current node
% (this is the other node of the current edge)
if edges(e,1)==n
n = edges(e,2);
else
n = edges(e,1);
end
% if node is same as start node, loop is closed, and we stop
% node iteration.
if n==n0
break;
end
end
% remove the last edge of the curve from edge list.
edges = edges((1:size(edges,1))~=e,:);
% add the current curve to the list, and start a new curve
c = c+1;
curves{c} = curve; %#ok<AGROW>
end
if nargout == 1
varargout = {curves};
end
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