From 643c2e6f219b01dc2fd9c8afc3f00d01595c6ddb Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Thu, 9 Jul 2015 16:31:40 -0600
Subject: [PATCH] Only update canvas if not dirty

---
 src/ol/source/rastersource.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/ol/source/rastersource.js b/src/ol/source/rastersource.js
index 0bbe181d81..02ed2c6879 100644
--- a/src/ol/source/rastersource.js
+++ b/src/ol/source/rastersource.js
@@ -318,7 +318,10 @@ ol.source.Raster.prototype.onWorkerComplete_ =
   this.dispatchEvent(new ol.source.RasterEvent(
       ol.source.RasterEventType.AFTEROPERATIONS, frameState, data));
 
-  this.canvasContext_.putImageData(output, 0, 0);
+  var resolution = frameState.viewState.resolution / frameState.pixelRatio;
+  if (!this.isDirty_(frameState.extent, resolution)) {
+    this.canvasContext_.putImageData(output, 0, 0);
+  }
 
   callback(null);
 };