Added active flag to avoid transform of inactive deepzoom images.

dist/iwmlib.js

@@ -2995,11 +2995,16 @@
             }
         }
 
+        _throwDeltaTime() {
+            let t = performance.now();
+            let dt = t - this.lastframe;
+            this.lastframe = t;
+            return dt
+        }
+
         animateThrow(time) {
             if (this.velocity != null) {
-                let t = performance.now();
-                let dt = t - this.lastframe;
-                this.lastframe = t;
+                let dt = this._throwDeltaTime();
                 // console.log("animateThrow", dt)
                 let next = this.nextVelocity(this.velocity);
                 let prevLength = Points.length(this.velocity);