melder/vendor/Shapefile/Geometry/Linestring.php

219 lines
6.2 KiB
PHP
Raw Normal View History

2024-02-16 15:35:01 +01:00
<?php
/**
* PHP Shapefile - PHP library to read and write ESRI Shapefiles, compatible with WKT and GeoJSON
*
* @package Shapefile
* @author Gaspare Sganga
2024-03-13 12:03:56 +01:00
* @version 4.0.0dev
2024-02-16 15:35:01 +01:00
* @license MIT
* @link https://gasparesganga.com/labs/php-shapefile/
*/
namespace Shapefile\Geometry;
use Shapefile\Shapefile;
use Shapefile\ShapefileException;
/**
* Linestring Geometry.
*
* - Array: [
* [numpoints] => int
* [points] => [
* [
* [x] => float
* [y] => float
* [z] => float
* [m] => float/bool
* ]
* ]
* ]
*
* - WKT:
* LINESTRING [Z][M] (x y z m, x y z m)
*
* - GeoJSON:
* {
* "type": "LineString" / "LineStringM"
* "coordinates": [
* [x, y, z] / [x, y, m] / [x, y, z, m]
* ]
* }
*/
class Linestring extends MultiPoint
{
/**
* WKT and GeoJSON basetypes, collection class type
*/
const WKT_BASETYPE = 'LINESTRING';
const GEOJSON_BASETYPE = 'LineString';
const COLLECTION_CLASS = 'Point';
/////////////////////////////// PUBLIC ///////////////////////////////
/**
* Checks whether the linestring is a closed ring or not.
* A closed ring has at least 4 vertices and the first and last ones must be the same.
*
* @return bool
*/
public function isClosedRing()
{
return $this->getNumPoints() >= 4 && $this->getPoint(0) == $this->getPoint($this->getNumPoints() - 1);
}
/**
* Forces the linestring to be a closed ring.
*
* @return self Returns $this to provide a fluent interface.
*/
public function forceClosedRing()
{
if (!$this->checkRingNumPoints()) {
throw new ShapefileException(Shapefile::ERR_GEOM_RING_NOT_ENOUGH_VERTICES);
}
if (!$this->isClosedRing()) {
$this->addPoint($this->getPoint(0));
}
return $this;
}
/**
* Checks whether a ring is clockwise or not (it works with open rings too).
*
* Throws an exception if ring area is too small and cannot determine its orientation.
* Returns Shapefile::UNDEFINED or throw an exception if there are not enough points.
*
* @param bool $flag_throw_exception Optional flag to throw an exception if there are not enough points.
*
* @return bool|Shapefile::UNDEFINED
*/
public function isClockwise($flag_throw_exception = false)
{
if ($this->isEmpty()) {
return Shapefile::UNDEFINED;
}
if (!$this->checkRingNumPoints()) {
if ($flag_throw_exception) {
throw new ShapefileException(Shapefile::ERR_GEOM_RING_NOT_ENOUGH_VERTICES);
}
return Shapefile::UNDEFINED;
}
$area = $this->computeGaussArea($this->getArray()['points']);
if (!$area) {
throw new ShapefileException(Shapefile::ERR_GEOM_RING_AREA_TOO_SMALL);
}
// Negative area means clockwise direction
return $area < 0;
}
/**
* Forces the ring to be in clockwise direction (it works with open rings too).
* Throws an exception if direction is undefined.
*
* @return self Returns $this to provide a fluent interface.
*/
public function forceClockwise()
{
if ($this->isClockwise(true) === false) {
$this->reverseGeometries();
}
return $this;
}
/**
* Forces the ring to be in counterclockwise direction (it works with open rings too).
* Throws an exception if direction is undefined.
*
* @return self Returns $this to provide a fluent interface.
*/
public function forceCounterClockwise()
{
if ($this->isClockwise(true) === true) {
$this->reverseGeometries();
}
return $this;
}
public function getSHPBasetype()
{
return Shapefile::SHAPE_TYPE_POLYLINE;
}
/////////////////////////////// PROTECTED ///////////////////////////////
protected function getWKTBasetype()
{
return static::WKT_BASETYPE;
}
protected function getGeoJSONBasetype()
{
return static::GEOJSON_BASETYPE;
}
protected function getCollectionClass()
{
return __NAMESPACE__ . '\\' . static::COLLECTION_CLASS;
}
/////////////////////////////// PRIVATE ///////////////////////////////
/**
* Checks if the linestring has enough points to be a ring.
*/
private function checkRingNumPoints()
{
return $this->getNumPoints() >= 3;
}
/**
* Computes ring area using a Gauss-like formula.
* The target is to determine whether it is positive or negative, not the exact area.
*
* An optional $exp parameter is used to deal with very small areas.
*
* @param array $points Array of points. Each element must have "x" and "y" members.
* @param int $exp Optional exponent to deal with small areas (coefficient = 10^exponent).
*
* @return float
*/
private function computeGaussArea($points, $exp = 0)
{
2024-03-13 12:03:56 +01:00
// If a coefficient of 10^12 is not enough, give up!
if ($exp > 12) {
2024-02-16 15:35:01 +01:00
return 0;
}
$coef = pow(10, $exp);
// At least 3 points (in case of an open ring) are needed to compute the area
$num_points = count($points);
if ($num_points < 3) {
return 0;
}
// Use Gauss's area formula (no need to be strict here, hence no 1/2 coefficient and no check for closed rings)
$num_points--;
$tot = 0;
for ($i = 0; $i < $num_points; ++$i) {
$tot += ($coef * $points[$i]['x'] * $points[$i + 1]['y']) - ($coef * $points[$i]['y'] * $points[$i + 1]['x']);
}
$tot += ($coef * $points[$num_points]['x'] * $points[0]['y']) - ($coef * $points[$num_points]['y'] * $points[0]['x']);
// If area is too small, increase coefficient exponent and retry
if ($tot == 0) {
return $this->computeGaussArea($points, $exp + 3);
}
return $tot;
}
}