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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''
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## The views and conclusions contained in the software and documentation are
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function [dist, proj] = distancePointEllipse(point, elli)
%DISTANCEPOINTELLIPSE Distance from a point to an ellipse.
%
% DIST = distancePointEllipse(POINT, ELLI)
% Computes the Euclidean distance between the point POINT and the ellipse
% ELLI.
% POINT may also be a N-by-2 array of point coordinates. In that case the
% result is a N-by-1 array of distances.
%
% [DIST, PROJ] = distancePointEllipse(POINT, ELLI)
% Also return the coordinates of the projection of the point onto the
% ellipse. PROJ has same dimensions as the array POINT.
%
% Example
% % create an ellipse
% elli = [50 50 40 30 20];
% % generate points along a regular grid
% [x, y] = meshgrid(1:100, 1:100);
% pts = [x(:) y(:)];
% % compute distance map
% distMap = reshape(distancePointEllipse(pts, elli), size(x));
% figure; imshow(distMap, []); colormap parula;
%
%
% References:
% https://blog.chatfield.io/simple-method-for-distance-to-ellipse/
%
% See also
% ellipses2d, projPointOnEllipse, distancePoints
%
% ------
% Author: David Legland
% E-mail: david.legland@inrae.fr
% Created: 2022-07-17, using Matlab 9.12.0.1884302 (R2022a)
% Copyright 2022-2023 INRAE - BIA Research Unit - BIBS Platform (Nantes)
proj = projPointOnEllipse(point, elli);
dist = distancePoints(point, proj, 'diag');
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