- Optimized algorithm for polygon size reducement

1 files changed, 21 insertions, 14 deletions

diff --git a/src/interfaces/driver.php b/src/interfaces/driver.php
index 354050f..ef7f57a 100644
--- a/src/interfaces/driver.php
+++ b/src/interfaces/driver.php
@@ -135,6 +135,27 @@ abstract class ezcGraphDriver
             return $points;
         }
 
+        // Determine one of the angles - we need to know where the smaller
+        // angle is, to determine if the inner side of the polygon is on
+        // the left or right hand.
+        //
+        // This is a valid simplification for ezcGraph(, for now).
+        //
+        // The sign of the scalar products results indicates on which site
+        // the smaller angle is, when comparing the orthogonale vector of 
+        // one of the vectors with the other. Why? .. use pen and paper ..
+        //
+        // It is sufficant to do this once before iterating over the points, 
+        // because the inner side of the polygon is on the same side of the 
+        // point for each point.
+        $last = 0;
+        $next = 1;
+
+        $sign = ( 
+                -$vectors[$last]->y * $vectors[$next]->x +
+                $vectors[$last]->x * $vectors[$next]->y 
+            ) < 0 ? 1 : -1;
+
         // Move points to center
         $newPoints = array();
         for ( $i = 0; $i < $pointCount; ++$i )
@@ -142,20 +163,6 @@ abstract class ezcGraphDriver
             $last = $i;
             $next = ( $i + 1 ) % $pointCount;
 
-            // Determine one of the angles - we need to know where the smaller
-            // angle is, to determine if the inner side of the polygon is on
-            // the left or right hand.
-            //
-            // This is a valid simplification for ezcGraph(, for now).
-            //
-            // The sign of the scalar products results indicates on which site
-            // the smaller angle is, when comparing the orthogonale vector of 
-            // one of the vectors with the other. Why? .. use pen and paper ..
-            $sign = ( 
-                    -$vectors[$last]->y * $vectors[$next]->x +
-                    $vectors[$last]->x * $vectors[$next]->y 
-                ) < 0 ? 1 : -1;
-            
             // Orthogonal vector with direction based on the side of the inner
             // angle
             $v = clone $vectors[$next];