From 097714cf39eac703a30ffd704a816d50d4426d79 Mon Sep 17 00:00:00 2001
From: Dominik Picheta <dominikpicheta@googlemail.com>
Date: Wed, 20 Aug 2014 09:58:40 +0100
Subject: [PATCH] Implements pinch rotate.

---
 src/viewer.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/viewer.js b/src/viewer.js
index 5435b3a0..0df3e77a 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -2465,6 +2465,12 @@ function onCanvasPinch( event ) {
             this.viewport.applyConstraints();
         }
     }
+    // Pinch rotate
+    var angle1 = Math.atan2(event.gesturePoints[0].currentPos.y - event.gesturePoints[1].currentPos.y,
+        event.gesturePoints[0].currentPos.x - event.gesturePoints[1].currentPos.x);
+    var angle2 = Math.atan2(event.gesturePoints[0].lastPos.y - event.gesturePoints[1].lastPos.y,
+        event.gesturePoints[0].lastPos.x - event.gesturePoints[1].lastPos.x);
+    this.viewport.setRotation(this.viewport.getRotation() + ((angle1 - angle2) * (180 / Math.PI)));
     /**
      * Raised when a pinch event occurs on the {@link OpenSeadragon.Viewer#canvas} element.
      *