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vendor/Shapefile/Geometry/Linestring.php

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+<?php
+
+/**
+ * PHP Shapefile - PHP library to read and write ESRI Shapefiles, compatible with WKT and GeoJSON
+ *
+ * @package Shapefile
+ * @author  Gaspare Sganga
+ * @version 3.3.0
+ * @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, $exp = 0)
+    {
+        // If a coefficient of 10^9 is not enough, give up!
+        if ($exp > 9) {
+            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;
+    }
+}