Merge pull request #2066 from kim-sanghoon/feature/setMaxLevel

Fix #2065 and add setMaxLevel for #2059

src/tilesource.js

@@ -275,28 +275,43 @@ $.TileSource.prototype = {
         return this._tileHeight;
     },
 
+    /**
+     * Set the maxLevel to the given level, and perform the memoization of
+     * getLevelScale with the new maxLevel. This function can be useful if the
+     * memoization is required before the first call of getLevelScale, or both
+     * memoized getLevelScale and maxLevel should be changed accordingly.
+     * @function
+     * @param {Number} level
+     */
+    setMaxLevel: function( level ) {
+        this.maxLevel = level;
+        this._memoizeLevelScale();
+    },
+
     /**
      * @function
      * @param {Number} level
      */
     getLevelScale: function( level ) {
+        // if getLevelScale is not memoized, we generate the memoized version
+        // at the first call and return the result
+        this._memoizeLevelScale();
+        return this.getLevelScale( level );
+    },
 
+    // private
+    _memoizeLevelScale: function() {
         // see https://github.com/openseadragon/openseadragon/issues/22
         // we use the tilesources implementation of getLevelScale to generate
         // a memoized re-implementation
-        var maxLevel = Math.ceil(
+        var levelScaleCache = {},
-                Math.log( Math.max( this.dimensions.x, this.dimensions.y ) ) /
-                Math.log( 2 )
-            ),
-            levelScaleCache = {},
             i;
-        for( i = 0; i <= maxLevel; i++ ){
+        for( i = 0; i <= this.maxLevel; i++ ){
-            levelScaleCache[ i ] = 1 / Math.pow(2, maxLevel - i);
+            levelScaleCache[ i ] = 1 / Math.pow(2, this.maxLevel - i);
         }
         this.getLevelScale = function( _level ){
             return levelScaleCache[ _level ];
         };
-        return this.getLevelScale( level );
     },
 
     /**

test/modules/tilesource.js

@@ -128,8 +128,6 @@
 
         assert.equal(tileSource.maxLevel, 12, 'The initial max level should be 12.');
 
-        tileSource.maxLevel = 9;
-
         function assertLevelScale(level, expected) {
             var actual = tileSource.getLevelScale(level);
             assert.ok(Math.abs(actual - expected) < Number.EPSILON, "The scale at level " + level +
@@ -141,6 +139,13 @@
         assertLevelScale(10, 1 / 4);
         assertLevelScale(8, 1 / 16);
         assertLevelScale(6, 1 / 64);
+
+        tileSource.setMaxLevel(9);
+
+        assertLevelScale(9, 1);
+        assertLevelScale(7, 1 / 4);
+        assertLevelScale(5, 1 / 16);
+        assertLevelScale(3, 1 / 64);
     });
 
 }());