mirror of
https://github.com/Karaka-Management/phpOMS.git
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122 lines
3.1 KiB
PHP
122 lines
3.1 KiB
PHP
<?php
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/**
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* Jingga
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*
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* PHP Version 8.1
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*
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* @package phpOMS\Math\Geometry\ConvexHull
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* @copyright Dennis Eichhorn
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* @license OMS License 2.0
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* @version 1.0.0
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* @link https://jingga.app
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*/
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declare(strict_types=1);
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namespace phpOMS\Math\Geometry\ConvexHull;
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/**
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* Andrew's monotone chain convex hull algorithm class.
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*
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* @package phpOMS\Math\Geometry\ConvexHull
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* @license OMS License 2.0
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* @link https://jingga.app
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* @since 1.0.0
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*/
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final class GrahamScan
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{
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/**
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* Constructor.
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*
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* @since 1.0.0
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* @codeCoverageIgnore
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*/
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private function __construct()
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{
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}
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/**
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* Create convex hull
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*
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* @param array<int, array{x:int|float, y:int|float}> $points Points (Point Cloud)
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*
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* @return array<int, array{x:int|float, y:int|float}>
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*
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* @since 1.0.0
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*/
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public static function createConvexHull(array $points) : array
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{
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if (($n = \count($points)) < 3) {
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return $points;
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}
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$min = 1;
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$points = \array_merge([null], $points);
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for ($i = 2; $i < $n; ++$i) {
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if ($points[$i]['y'] < $points[$min]['y']
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|| ($points[$i]['y'] === $points[$min]['y'] && $points[$i]['x'] < $points[$min]['x'])
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) {
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$min = $i;
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}
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}
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$temp = $points[1];
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$points[1] = $points[$min];
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$points[$min] = $temp;
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$c = $points[1];
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/** @var array<int, array{x:int|float, y:int|float}> $subpoints */
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$subpoints = \array_slice($points, 2, $n);
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\usort($subpoints, function (array $a, array $b) use ($c) : int {
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// @todo Might be wrong order of comparison
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return \atan2($a['y'] - $c['y'], $a['x'] - $c['x']) <=> \atan2($b['y'] - $c['y'], $b['x'] - $c['x']);
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});
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/** @var array<int, array{x:int|float, y:int|float}> $points */
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$points = \array_merge([$points[0], $points[1]], $subpoints);
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$points[0] = $points[$n];
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$size = 1;
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for ($i = 2; $i <= $n; ++$i) {
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while (self::ccw($points[$size - 1], $points[$size], $points[$i]) <= 0) {
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if ($size > 1) {
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--$size;
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} elseif ($i === $n) {
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break;
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} else {
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++$i;
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}
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}
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$temp = $points[$i];
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$points[$size + 1] = $points[$i];
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$points[$i] = $points[$size + 1];
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++$size;
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}
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$hull = [];
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for ($i = 1; $i <= $size; ++$i) {
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$hull[] = $points[$i];
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}
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return $hull;
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}
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/**
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* Counterclockwise rotation
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*
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* @param array{x:int|float, y:int|float} $a Vector
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* @param array{x:int|float, y:int|float} $b Vector
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* @param array{x:int|float, y:int|float} $c Vector
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*
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* @return int|float
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*
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* @since 1.0.0
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*/
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public static function ccw(array $a, array $b, array $c) : int|float
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{
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return (($b['x'] - $a['x']) * ($c['y'] - $a['y']) - ($b['y'] - $a['y']) * ($c['x'] - $a['x']));
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}
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}
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