Align pixels when drawing icons or shapes

The floor before setting the transform ensures that we translate by integer pixels for odd and even dimenstions.  The round before drawing the image ensures pixels are aligned.

src/ol/renderer/canvas/canvasvectorrenderer.js

@@ -238,8 +238,8 @@ ol.renderer.canvas.Vector.prototype.renderPointFeatures_ =
     return true;
   }
 
-  var midWidth = content.width / 2;
+  var midWidth = Math.floor(content.width / 2);
-  var midHeight = content.height / 2;
+  var midHeight = Math.floor(content.height / 2);
   var contentWidth = content.width * this.inverseScale_;
   var contentHeight = content.height * this.inverseScale_;
   var contentXOffset = xOffset * this.inverseScale_;
@@ -276,7 +276,8 @@ ol.renderer.canvas.Vector.prototype.renderPointFeatures_ =
       point = components[j];
       vec = [point.get(0), point.get(1), 0];
       goog.vec.Mat4.multVec3(this.transform_, vec, vec);
-      context.drawImage(content, vec[0] + xOffset, vec[1] + yOffset,
+      context.drawImage(content, Math.round(vec[0] + xOffset),
+          Math.round(vec[1] + yOffset),
           content.width, content.height);
     }
   }