Adding option for areas to output signed (negative) areas. Chaning ce…

…ntroid method to use signed-areas
mariomartinezsz · Jan 9, 2012 · 0ad1656 · 0ad1656
1 parent d8c7c1e
commit 0ad1656
Showing 1 changed file with 6 additions and 4 deletions.
diff --git a/lib/geometry/Polygon.class.php b/lib/geometry/Polygon.class.php
@@ -34,7 +34,7 @@ public function __construct(array $linestrings) {
     }
   }
 
-  public function area($exterior_only = FALSE) {
+  public function area($exterior_only = FALSE, $signed = FALSE) {
     if ($this->geos() && $exterior_only == FALSE) {
       return $this->geos()->area();
     }
@@ -50,7 +50,9 @@ public function area($exterior_only = FALSE) {
       $a = $a + ($p->getX() * $pts[$j]->getY()) - ($p->getY() * $pts[$j]->getX());
     }
 
-    $area = abs(($a / 2));
+    if ($signed) $area = ($a / 2);
+    else $area = abs(($a / 2));
+
     if ($exterior_only == TRUE) {
       return $area;
     }
@@ -74,7 +76,7 @@ public function centroid() {
     $c = count($pts);
     if((int)$c == '0') return NULL;
     $cn = array('x' => '0', 'y' => '0');
-    $a = $this->area(TRUE);
+    $a = $this->area(TRUE, TRUE);
 
     // If this is a polygon with no area. Just return the first point.
     if ($a == 0) {
@@ -90,7 +92,7 @@ public function centroid() {
 
     $cn['x'] = $cn['x'] / ( 6 * $a);
     $cn['y'] = $cn['y'] / ( 6 * $a);
-        
+
     $centroid = new Point($cn['x'], $cn['y']);
     return $centroid;
   }