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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 edge2 = clipEdge(edge, box)
%CLIPEDGE Clip an edge with a rectangular box.
%
% EDGE2 = clipEdge(EDGE, BOX);
% EDGE: [x1 y1 x2 y2],
% BOX : [xmin xmax ymin ymax], or [xmin xmax ; ymin ymax].
% return :
% EDGE2 = [xc1 yc1 xc2 yc2];
%
% If clipping is null, return [0 0 0 0];
%
% if EDGE is a N-by-4 array, return an N-by-4 array, corresponding to
% each clipped edge.
%
% See also
% edges2d, boxes2d, clipLine
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2005-05-14
% Copyright 2005-2023 INRA - Cepia Software Platform
% process data input
if size(box, 1) == 2
box = box';
end
% get limits of window
xmin = box(1);
xmax = box(2);
ymin = box(3);
ymax = box(4);
% convert window limits into lines
lineX0 = [xmin ymin xmax-xmin 0];
lineX1 = [xmin ymax xmax-xmin 0];
lineY0 = [xmin ymin 0 ymax-ymin];
lineY1 = [xmax ymin 0 ymax-ymin];
% compute outcodes of each vertex
p11 = edge(:,1) < xmin; p21 = edge(:,3) < xmin;
p12 = edge(:,1) > xmax; p22 = edge(:,3) > xmax;
p13 = edge(:,2) < ymin; p23 = edge(:,4) < ymin;
p14 = edge(:,2) > ymax; p24 = edge(:,4) > ymax;
out1 = [p11 p12 p13 p14];
out2 = [p21 p22 p23 p24];
% detect edges totally inside window -> no clip.
inside = sum(out1 | out2, 2) == 0;
% detect edges totally outside window
outside = sum(out1 & out2, 2) > 0;
% select edges not totally outside, and process separately edges totally
% inside window
ind = find(~(inside | outside));
% allocate memroty for all clipped edges
edge2 = zeros(size(edge));
% copy result of edges totally inside clipping box
edge2(inside, :) = edge(inside, :);
% iterate over edges
for i = 1:length(ind)
% current edge
iedge = edge(ind(i), :);
% compute intersection points with each line of bounding window
px0 = intersectLineEdge(lineX0, iedge);
px1 = intersectLineEdge(lineX1, iedge);
py0 = intersectLineEdge(lineY0, iedge);
py1 = intersectLineEdge(lineY1, iedge);
% create array of points
points = [px0; px1; py0; py1; iedge(1:2); iedge(3:4)];
% remove infinite points (edges parallel to box edges)
points = points(all(isfinite(points), 2), :);
% sort points by x then y
points = sortrows(points);
% get center positions between consecutive points
centers = (points(2:end,:) + points(1:end-1,:))/2;
% find the centers (if any) inside window
inside = find( centers(:,1) >= xmin & centers(:,2) >= ymin & ...
centers(:,1) <= xmax & centers(:,2) <= ymax);
% if multiple segments are inside box, which can happen due to finite
% resolution, only take the longest segment
if length(inside) > 1
% compute delta vectors of the segments
dv = points(inside+1,:) - points(inside,:);
% compute lengths of segments
len = hypot(dv(:,1), dv(:,2));
% find index of longest segment
[a, I] = max(len); %#ok<ASGLU>
inside = inside(I);
end
% if one of the center points is inside box, then the according edge
% segment is indide box
if length(inside) == 1
% restore same direction of edge
if iedge(1) > iedge(3) || (iedge(1) == iedge(3) && iedge(2) > iedge(4))
edge2(ind(i), :) = [points(inside+1,:) points(inside,:)];
else
edge2(ind(i), :) = [points(inside,:) points(inside+1,:)];
end
end
end % end of loop over edges
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