diff --git a/src/tiledimage.js b/src/tiledimage.js
index e8092083..4291bf85 100644
--- a/src/tiledimage.js
+++ b/src/tiledimage.js
@@ -146,6 +146,7 @@ $.TiledImage = function( options ) {
         _midDraw:       false, // Is the tiledImage currently updating the viewport?
         _needsDraw:     true,  // Does the tiledImage need to update the viewport again?
         _hasOpaqueTile: false,  // Do we have even one fully opaque tile?
+        _tilesLoading:  0,     // The number of pending tile requests.
         //configurable settings
         springStiffness:        $.DEFAULT_SETTINGS.springStiffness,
         animationTime:          $.DEFAULT_SETTINGS.animationTime,
@@ -898,6 +899,7 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
     // private
     _updateViewport: function() {
         this._needsDraw = false;
+        this._tilesLoading = 0;
 
         // Reset tile's internal drawn state
         while (this.lastDrawn.length > 0) {
@@ -994,8 +996,49 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
             this._needsDraw = true;
             this._setFullyLoaded(false);
         } else {
-            this._setFullyLoaded(true);
+            this._setFullyLoaded(this._tilesLoading === 0);
         }
+    },
+
+    // private
+    _getCornerTiles: function(level, topLeftBound, bottomRightBound) {
+        var leftX;
+        var rightX;
+        if (this.wrapHorizontal) {
+            leftX = $.positiveModulo(topLeftBound.x, 1);
+            rightX = $.positiveModulo(bottomRightBound.x, 1);
+        } else {
+            leftX = Math.max(0, topLeftBound.x);
+            rightX = Math.min(1, bottomRightBound.x);
+        }
+        var topY;
+        var bottomY;
+        var aspectRatio = 1 / this.source.aspectRatio;
+        if (this.wrapVertical) {
+            topY = $.positiveModulo(topLeftBound.y, aspectRatio);
+            bottomY = $.positiveModulo(bottomRightBound.y, aspectRatio);
+        } else {
+            topY = Math.max(0, topLeftBound.y);
+            bottomY = Math.min(aspectRatio, bottomRightBound.y);
+        }
+
+        var topLeftTile = this.source.getTileAtPoint(level, new $.Point(leftX, topY));
+        var bottomRightTile = this.source.getTileAtPoint(level, new $.Point(rightX, bottomY));
+        var numTiles  = this.source.getNumTiles(level);
+
+        if (this.wrapHorizontal) {
+            topLeftTile.x += numTiles.x * Math.floor(topLeftBound.x);
+            bottomRightTile.x += numTiles.x * Math.floor(bottomRightBound.x);
+        }
+        if (this.wrapVertical) {
+            topLeftTile.y += numTiles.y * Math.floor(topLeftBound.y / aspectRatio);
+            bottomRightTile.y += numTiles.y * Math.floor(bottomRightBound.y / aspectRatio);
+        }
+
+        return {
+            topLeft: topLeftTile,
+            bottomRight: bottomRightTile,
+        };
     }
 });
 
@@ -1039,23 +1082,13 @@ function updateLevel(tiledImage, haveDrawn, drawLevel, level, levelOpacity,
         });
     }
 
-    //OK, a new drawing so do your calculations
-    var topLeftTile = tiledImage.source.getTileAtPoint(level, topLeftBound);
-    var bottomRightTile = tiledImage.source.getTileAtPoint(level, bottomRightBound);
-    var numberOfTiles  = tiledImage.source.getNumTiles(level);
-
     resetCoverage(tiledImage.coverage, level);
 
-    if (!tiledImage.wrapHorizontal) {
-        // Adjust for floating point error
-        topLeftTile.x = Math.max(topLeftTile.x, 0);
-        bottomRightTile.x = Math.min(bottomRightTile.x, numberOfTiles.x - 1);
-    }
-    if (!tiledImage.wrapVertical) {
-        // Adjust for floating point error
-        topLeftTile.y = Math.max(topLeftTile.y, 0);
-        bottomRightTile.y = Math.min(bottomRightTile.y, numberOfTiles.y - 1);
-    }
+    //OK, a new drawing so do your calculations
+    var cornerTiles = tiledImage._getCornerTiles(level, topLeftBound, bottomRightBound);
+    var topLeftTile = cornerTiles.topLeft;
+    var bottomRightTile = cornerTiles.bottomRight;
+    var numberOfTiles  = tiledImage.source.getNumTiles(level);
 
     var viewportCenter = tiledImage.viewport.pixelFromPoint(
         tiledImage.viewport.getCenter());
@@ -1178,7 +1211,7 @@ function updateTile( tiledImage, drawLevel, haveDrawn, x, y, level, levelOpacity
         }
     } else if ( tile.loading ) {
         // the tile is already in the download queue
-        // thanks josh1093 for finally translating this typo
+        tiledImage._tilesLoading++;
     } else {
         best = compareTiles( best, tile );
     }
diff --git a/src/tilesource.js b/src/tilesource.js
index fa52f61e..74d7c315 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -345,18 +345,17 @@ $.TileSource.prototype = {
      * @param {OpenSeadragon.Point} point
      */
     getTileAtPoint: function(level, point) {
+        var validPoint = point.x >= 0 && point.x <= 1 &&
+            point.y >= 0 && point.y <= 1 / this.aspectRatio;
+        $.console.assert(validPoint, "[TileSource.getTileAtPoint] must be called with a valid point.");
+
         var widthScaled = this.dimensions.x * this.getLevelScale(level);
-        var pixelX = $.positiveModulo(point.x, 1) * widthScaled;
-        var pixelY = $.positiveModulo(point.y, 1 / this.aspectRatio) * widthScaled;
+        var pixelX = point.x * widthScaled;
+        var pixelY = point.y * widthScaled;
 
         var x = Math.floor(pixelX / this.getTileWidth());
         var y = Math.floor(pixelY / this.getTileHeight());
 
-        // Fix for wrapping
-        var numTiles = this.getNumTiles(level);
-        x += numTiles.x * Math.floor(point.x);
-        y += numTiles.y * Math.floor(point.y * this.aspectRatio);
-
         return new $.Point(x, y);
     },
 
diff --git a/test/coverage.html b/test/coverage.html
index b04d5fda..65711abc 100644
--- a/test/coverage.html
+++ b/test/coverage.html
@@ -32,6 +32,7 @@
     <script src="/src/iiiftilesource.js"></script>
     <script src="/src/osmtilesource.js"></script>
     <script src="/src/tmstilesource.js"></script>
+    <script src="/src/zoomifytilesource.js"></script>
     <script src="/src/legacytilesource.js"></script>
     <script src="/src/imagetilesource.js"></script>
     <script src="/src/tilesourcecollection.js"></script>
diff --git a/test/modules/basic.js b/test/modules/basic.js
index c6164560..4d787ab4 100644
--- a/test/modules/basic.js
+++ b/test/modules/basic.js
@@ -331,7 +331,7 @@
                     height: 155
                 } ]
         } );
-        viewer.addHandler('tile-drawn', function() {
+        viewer.addOnceHandler('tile-drawn', function() {
             ok(OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                 "Canvas should be tainted.");
             start();
@@ -355,7 +355,7 @@
                             height: 155
                         } ]
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(!OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should not be tainted.");
                     start();
@@ -385,7 +385,7 @@
                     },
                     crossOriginPolicy : false
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should be tainted.");
                     start();
@@ -414,7 +414,7 @@
                         crossOriginPolicy : "Anonymous"
                     }
                 } );
-                viewer.addHandler('tile-drawn', function() {
+                viewer.addOnceHandler('tile-drawn', function() {
                     ok(!OpenSeadragon.isCanvasTainted(viewer.drawer.context.canvas),
                         "Canvas should not be tainted.");
                     start();
diff --git a/test/modules/multi-image.js b/test/modules/multi-image.js
index 4cbd5211..1dc9cbca 100644
--- a/test/modules/multi-image.js
+++ b/test/modules/multi-image.js
@@ -217,7 +217,7 @@
             var firstImage = viewer.world.getItemAt(0);
             firstImage.addHandler('fully-loaded-change', function() {
                 var imageData = viewer.drawer.context.getImageData(0, 0,
-                    500 * OpenSeadragon.pixelDensityRatio, 500 * density);
+                    500 * density, 500 * density);
 
                 // Pixel 250,250 will be in the hole of the A
                 var expectedVal = getPixelValue(imageData, 250 * density, 250 * density);
diff --git a/test/modules/tiledimage.js b/test/modules/tiledimage.js
index 20171432..1b05b557 100644
--- a/test/modules/tiledimage.js
+++ b/test/modules/tiledimage.js
@@ -515,4 +515,159 @@
         }]);
     });
 
+    // PhantomJS is missing Function.prototype.bind
+    function bind(func, _this) {
+        return function() {
+            return func.apply(_this, arguments);
+        };
+    }
+
+    test('_getCornerTiles without wrapping', function() {
+        var tiledImageMock = {
+            wrapHorizontal: false,
+            wrapVertical: false,
+            source: new OpenSeadragon.TileSource({
+                width: 1500,
+                height: 1000,
+                tileWidth: 200,
+                tileHeight: 150,
+                tileOverlap: 1,
+            }),
+        };
+        var _getCornerTiles = bind(
+            OpenSeadragon.TiledImage.prototype._getCornerTiles,
+            tiledImageMock);
+
+        function assertCornerTiles(topLeftBound, bottomRightBound,
+            expectedTopLeft, expectedBottomRight) {
+            var cornerTiles = _getCornerTiles(11, topLeftBound, bottomRightBound);
+            ok(cornerTiles.topLeft.equals(expectedTopLeft),
+                'Top left tile should be ' + expectedTopLeft.toString() +
+                ' found ' + cornerTiles.topLeft.toString());
+            ok(cornerTiles.bottomRight.equals(expectedBottomRight),
+                'Bottom right tile should be ' + expectedBottomRight.toString() +
+                ' found ' + cornerTiles.bottomRight.toString());
+        }
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(1, 10 / 15),
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(7, 6)
+        )
+
+        // Floating point errors should be handled
+        assertCornerTiles(
+            new OpenSeadragon.Point(-1e-14, -1e-14),
+            new OpenSeadragon.Point(1 + 1e-14, 10 / 15 + 1e-14),
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(7, 6)
+        )
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0.3, 0.5),
+            new OpenSeadragon.Point(0.5, 0.6),
+            new OpenSeadragon.Point(2, 5),
+            new OpenSeadragon.Point(3, 6)
+        )
+    });
+
+    test('_getCornerTiles with horizontal wrapping', function() {
+        var tiledImageMock = {
+            wrapHorizontal: true,
+            wrapVertical: false,
+            source: new OpenSeadragon.TileSource({
+                width: 1500,
+                height: 1000,
+                tileWidth: 200,
+                tileHeight: 150,
+                tileOverlap: 1,
+            }),
+        };
+        var _getCornerTiles = bind(
+            OpenSeadragon.TiledImage.prototype._getCornerTiles,
+            tiledImageMock);
+
+        function assertCornerTiles(topLeftBound, bottomRightBound,
+            expectedTopLeft, expectedBottomRight) {
+            var cornerTiles = _getCornerTiles(11, topLeftBound, bottomRightBound);
+            ok(cornerTiles.topLeft.equals(expectedTopLeft),
+                'Top left tile should be ' + expectedTopLeft.toString() +
+                ' found ' + cornerTiles.topLeft.toString());
+            ok(cornerTiles.bottomRight.equals(expectedBottomRight),
+                'Bottom right tile should be ' + expectedBottomRight.toString() +
+                ' found ' + cornerTiles.bottomRight.toString());
+        }
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(1, 10 / 15),
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(8, 6)
+        )
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(-1, 0),
+            new OpenSeadragon.Point(0.5, 10 / 15 + 1e-14),
+            new OpenSeadragon.Point(-8, 0),
+            new OpenSeadragon.Point(3, 6)
+        )
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(1.3, 0.5),
+            new OpenSeadragon.Point(1.5, 0.6),
+            new OpenSeadragon.Point(10, 5),
+            new OpenSeadragon.Point(11, 6)
+        )
+    });
+
+    test('_getCornerTiles with vertical wrapping', function() {
+        var tiledImageMock = {
+            wrapHorizontal: false,
+            wrapVertical: true,
+            source: new OpenSeadragon.TileSource({
+                width: 1500,
+                height: 1000,
+                tileWidth: 200,
+                tileHeight: 150,
+                tileOverlap: 1,
+            }),
+        };
+        var _getCornerTiles = bind(
+            OpenSeadragon.TiledImage.prototype._getCornerTiles,
+            tiledImageMock);
+
+        function assertCornerTiles(topLeftBound, bottomRightBound,
+            expectedTopLeft, expectedBottomRight) {
+            var cornerTiles = _getCornerTiles(11, topLeftBound, bottomRightBound);
+            ok(cornerTiles.topLeft.equals(expectedTopLeft),
+                'Top left tile should be ' + expectedTopLeft.toString() +
+                ' found ' + cornerTiles.topLeft.toString());
+            ok(cornerTiles.bottomRight.equals(expectedBottomRight),
+                'Bottom right tile should be ' + expectedBottomRight.toString() +
+                ' found ' + cornerTiles.bottomRight.toString());
+        }
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(1, 10 / 15),
+            new OpenSeadragon.Point(0, 0),
+            new OpenSeadragon.Point(7, 7)
+        )
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0, -10 / 15 / 2),
+            new OpenSeadragon.Point(0.5, 0.5),
+            new OpenSeadragon.Point(0, -4),
+            new OpenSeadragon.Point(3, 5)
+        )
+
+        assertCornerTiles(
+            new OpenSeadragon.Point(0, 10 / 15 + 0.1),
+            new OpenSeadragon.Point(0.3, 10 / 15 + 0.3),
+            new OpenSeadragon.Point(0, 7),
+            new OpenSeadragon.Point(2, 9)
+        )
+    });
+
 })();
diff --git a/test/modules/tilesource.js b/test/modules/tilesource.js
index 59d8b77f..71fb053d 100644
--- a/test/modules/tilesource.js
+++ b/test/modules/tilesource.js
@@ -1,32 +1,32 @@
 /* global module, ok, equal, start, test, testLog, Util */
 (function() {
-    
+
     module('TileSource', {
         setup: function() {
             testLog.reset();
         }
     });
-    
-    
+
+
     test("should set sane tile size defaults", function() {
         var source = new OpenSeadragon.TileSource();
-        
+
         equal(source.getTileWidth(), 0, "getTileWidth() should return 0 if not provided a size");
         equal(source.getTileHeight(), 0, "getTileHeight() should return 0 if not provided a size");
     });
-    
+
     test("providing tileSize", function(){
         var tileSize = 256,
             source = new OpenSeadragon.TileSource({
                 tileSize: tileSize
             });
-        
+
         equal(source.tileSize, undefined, "tileSize should not be set on the tileSource");
         equal(source.getTileWidth(), tileSize, "getTileWidth() should equal tileSize");
         equal(source.getTileHeight(), tileSize, "getTileHeight() should equal tileSize");
     });
-    
-    
+
+
     test("providing tileWidth and tileHeight", function(){
         var tileWidth = 256,
             tileHeight = 512,
@@ -34,7 +34,7 @@
                 tileWidth: tileWidth,
                 tileHeight: tileHeight
             });
-        
+
         equal(source._tileWidth, tileWidth, "tileWidth option should set _tileWidth");
         equal(source._tileHeight, tileHeight, "tileHeight option should set _tileHeight");
         equal(source.tileWidth, undefined, "tileWidth should be renamed _tileWidth");
@@ -42,10 +42,49 @@
         equal(source.getTileWidth(), tileWidth, "getTileWidth() should equal tileWidth");
         equal(source.getTileHeight(), tileHeight, "getTileHeight() should equal tileHeight");
     });
-    
+
     test('getTileSize() deprecation', function() {
         var source = new OpenSeadragon.TileSource();
         Util.testDeprecation(source, 'getTileSize');
     });
 
+    test('getTileAtPoint', function() {
+        var tileSource = new OpenSeadragon.TileSource({
+            width: 1500,
+            height: 1000,
+            tileWidth: 200,
+            tileHeight: 150,
+            tileOverlap: 1,
+        });
+
+        equal(tileSource.maxLevel, 11, "The max level should be 11.");
+
+        function assertTileAtPoint(level, position, expected) {
+            var actual = tileSource.getTileAtPoint(level, position);
+            ok(actual.equals(expected), "The tile at level " + level +
+                ", position " + position.toString() +
+                " should be tile " + expected.toString() +
+                " got " + actual.toString());
+        }
+
+        assertTileAtPoint(11, new OpenSeadragon.Point(0, 0), new OpenSeadragon.Point(0, 0));
+        assertTileAtPoint(11, new OpenSeadragon.Point(0.5, 0.5), new OpenSeadragon.Point(3, 5));
+        assertTileAtPoint(11, new OpenSeadragon.Point(1, 10 / 15), new OpenSeadragon.Point(7, 6));
+
+        assertTileAtPoint(10, new OpenSeadragon.Point(0, 0), new OpenSeadragon.Point(0, 0));
+        assertTileAtPoint(10, new OpenSeadragon.Point(0.5, 0.5), new OpenSeadragon.Point(1, 2));
+        assertTileAtPoint(10, new OpenSeadragon.Point(1, 10 / 15), new OpenSeadragon.Point(3, 3));
+
+        assertTileAtPoint(9, new OpenSeadragon.Point(0, 0), new OpenSeadragon.Point(0, 0));
+        assertTileAtPoint(9, new OpenSeadragon.Point(0.5, 0.5), new OpenSeadragon.Point(0, 1));
+        assertTileAtPoint(9, new OpenSeadragon.Point(1, 10 / 15), new OpenSeadragon.Point(1, 1));
+
+        // For all other levels, there is only one tile.
+        for (var level = 8; level >= 0; level--) {
+            assertTileAtPoint(level, new OpenSeadragon.Point(0, 0), new OpenSeadragon.Point(0, 0));
+            assertTileAtPoint(level, new OpenSeadragon.Point(0.5, 0.5), new OpenSeadragon.Point(0, 0));
+            assertTileAtPoint(level, new OpenSeadragon.Point(1, 10 / 15), new OpenSeadragon.Point(0, 0));
+        }
+    });
+
 }());