added getScaleFromResolution() function to util, also added tests for both directions of the scale<->resolution tranformation functions, as well as the normalizeScale() function

git-svn-id: http://svn.openlayers.org/trunk/openlayers@1534 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Util.js

@@ -518,6 +518,26 @@ OpenLayers.Util.getResolutionFromScale = function (scale, units) {
     return resolution;
 };
 
+/**
+ * @param {float} resolution
+ * @param {String} units Index into OpenLayers.INCHES_PER_UNIT hashtable.
+ *                       Default is degrees
+ * 
+ * @returns The corresponding scale given passed-in resolution and unit 
+ *          parameters.
+ * @type float
+ */
+OpenLayers.Util.getScaleFromResolution = function (resolution, units) {
+
+    if (units == null) {
+        units = "degrees";
+    }
+
+    var scale = 1 / (resolution * OpenLayers.INCHES_PER_UNIT[units]
+                                    * OpenLayers.DOTS_PER_INCH);
+    return scale;
+};
+
 /** Safely stop the propagation of an event *without* preventing
  *   the default browser action from occurring.
  *