diff --git a/src/openseadragon.js b/src/openseadragon.js
index f035c436..71fca779 100644
--- a/src/openseadragon.js
+++ b/src/openseadragon.js
@@ -918,12 +918,11 @@ function OpenSeadragon( options ){
     };
 
     /**
-     * A ratio comparing the device screen's pixel density to the canvas's backing store pixel density,
-     * clamped to a minimum of 1. Defaults to 1 if canvas isn't supported by the browser.
-     * @member {Number} pixelDensityRatio
-     * @memberof OpenSeadragon
+     * @returns {Number} Return a ratio comparing the device screen's pixel
+     *  densityto the canvas's backing store pixel density, clamped to a
+     *  minimum of 1. Defaults to 1 if canvas isn't supported by the browser.
      */
-    $.pixelDensityRatio = (function () {
+    $.getCurrentPixelDensityRatio = function() {
         if ( $.supportsCanvas ) {
             var context = document.createElement('canvas').getContext('2d');
             var devicePixelRatio = window.devicePixelRatio || 1;
@@ -936,7 +935,13 @@ function OpenSeadragon( options ){
         } else {
             return 1;
         }
-    }());
+    };
+
+    /**
+     * @member {Number} pixelDensityRatio
+     * @memberof OpenSeadragon
+     */
+    $.pixelDensityRatio = $.getCurrentPixelDensityRatio();
 
 }( OpenSeadragon ));
 
diff --git a/src/viewer.js b/src/viewer.js
index 03b018bc..aba013d5 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -401,28 +401,6 @@ $.Viewer = function( options ) {
         debugGridColor:     this.debugGridColor
     });
 
-    function resize() {
-      console.log("Windows is resized...");
-      $.pixelDensityRatio = (function () {
-        if ( $.supportsCanvas ) {
-            var context = document.createElement('canvas').getContext('2d');
-            var devicePixelRatio = window.devicePixelRatio || 1;
-            var backingStoreRatio = context.webkitBackingStorePixelRatio ||
-            context.mozBackingStorePixelRatio ||
-            context.msBackingStorePixelRatio ||
-            context.oBackingStorePixelRatio ||
-            context.backingStorePixelRatio || 1;
-            return Math.max(devicePixelRatio, 1) / backingStoreRatio;
-        } else {
-            return 1;
-        }
-      }());
-      console.log("$.pixelDensityRatio", $.pixelDensityRatio);
-      _this.world.resetItems();
-      _this.forceRedraw();
-    }
-    $.addEvent( window, 'resize', resize );
-
     // Overlay container
     this.overlaysContainer    = $.makeNeutralElement( "div" );
     this.canvas.appendChild( this.overlaysContainer );
@@ -442,6 +420,9 @@ $.Viewer = function( options ) {
         }
     }
 
+    // Add updatePixelDensityRatio to resize event
+    $.addEvent( window, 'resize', this.updatePixelDensityRatio.bind(this) );
+
     //Instantiate a navigator if configured
     if ( this.showNavigator){
         this.navigator = new $.Navigator({
@@ -1620,6 +1601,21 @@ $.extend( $.Viewer.prototype, $.EventSource.prototype, $.ControlDock.prototype,
         return this.world.removeItem(drawer);
     },
 
+
+    /**
+     * Update pixel density ration, clears all tiles and triggers updates for
+     * all items.
+     */
+    updatePixelDensityRatio: function() {
+        var previusPixelDensityRatio = $.pixelDensityRatio;
+        var currentPixelDensityRatio = $.getCurrentPixelDensityRatio();
+        if (previusPixelDensityRatio !== currentPixelDensityRatio) {
+            $.pixelDensityRatio = currentPixelDensityRatio;
+            this.world.resetItems();
+            this.forceRedraw();
+        }
+    },
+
     /**
      * Force the viewer to redraw its contents.
      * @returns {OpenSeadragon.Viewer} Chainable.