File: orientedBoxToPolygon.m

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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 [tx, ty] = orientedBoxToPolygon(obox)
%ORIENTEDBOXTOPOLYGON Convert an oriented box to a polygon (set of vertices).
%
%   POLY = orientedBoxToPolygon(OBOX);
%   Converts the oriented box OBOX given either as [XC YC W H] or as 
%   [XC YC W H THETA] into a 4-by-2 array of double, containing coordinates
%   of box vertices. 
%   XC and YC are center of the box. W and H are the width and the height
%   (dimension in the main directions), and THETA is the orientation, in
%   degrees between 0 and 360.
%
%   Example
%     OBOX = [20 10  40 20 0];
%     RECT = orientedBoxToPolygon(OBOX)
%     RECT =
%         -20 -10 
%          20 -10 
%          20  10 
%         -20  10 
%
%
%   See also 
%   polygons2d, orientedBox, drawOrientedBox, rectToPolygon
%

% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2005-04-06
% Copyright 2005-2023 INRA - TPV URPOI - BIA IMASTE

% extract box parameters
theta = 0;
x = obox(1);
y = obox(2);
w = obox(3) / 2;  % easier to compute with w and h divided by 2
h = obox(4) / 2;
if length(obox) > 4
    theta = obox(5);
end

v = [cosd(theta); sind(theta)];
M = bsxfun (@times, [-1 1; 1 1; 1 -1; -1 -1], [w h]);
tx  = x + M * v;
ty  = y + M(4:-1:1,[2 1]) * v;

if nargout <= 1
  tx = [tx ty];
end