diff --git a/ScanDemoExample/scanlibrary/src/main/java/com/scanlibrary/PolygonView.java b/ScanDemoExample/scanlibrary/src/main/java/com/scanlibrary/PolygonView.java
index 362e4c76..4f61bf2d 100644
--- a/ScanDemoExample/scanlibrary/src/main/java/com/scanlibrary/PolygonView.java
+++ b/ScanDemoExample/scanlibrary/src/main/java/com/scanlibrary/PolygonView.java
@@ -238,7 +238,11 @@ public boolean onTouch(View v, MotionEvent event) {
                 default:
                     break;
             }
-            polygonView.invalidate();
+            if (eid == MotionEvent.ACTION_MOVE) {
+                polygonView.superInvalidate();
+            }else {
+                polygonView.invalidate();
+            }
             return true;
         }
     }
@@ -292,5 +296,61 @@ public boolean onTouch(View v, MotionEvent event) {
 
     }
 
+    public void invalidate() {
+
+        if (pointer1.getX() > pointer4.getX() && pointer1.getY() > pointer4.getY()) {
+            ImageView tempImageView = pointer4;
+            pointer4 = pointer1;
+            pointer1 = tempImageView;
+        }
+
+        if (pointer2.getY() > pointer3.getY() && pointer2.getX() < pointer3.getX()) {
+            ImageView tempImageView = pointer3;
+            pointer3 = pointer2;
+            pointer2 = tempImageView;
+        }
+
+        if (pointer1.getX() > pointer4.getX()) {
+            ImageView tempImageView = pointer4;
+            pointer4 = pointer3;
+            pointer3 = tempImageView;
+        }
+
+        if (pointer1.getY() > pointer3.getY()) {
+            ImageView tempImageView = pointer3;
+            pointer3 = pointer1;
+            pointer1 = tempImageView;
+        }
+
+        if (pointer2.getY() > pointer4.getY()) {
+            ImageView tempImageView = pointer4;
+            pointer4 = pointer2;
+            pointer2 = tempImageView;
+        }
+
 
+        if (pointer1.getX() > pointer2.getX()) {
+            ImageView tempImageView = pointer2;
+            pointer2 = pointer1;
+            pointer1 = tempImageView;
+        }
+
+        if (pointer3.getX() > pointer4.getX()) {
+            ImageView tempImageView = pointer4;
+            pointer4 = pointer3;
+            pointer3 = tempImageView;
+        }
+
+
+        midPointer13.setOnTouchListener(new MidPointTouchListenerImpl(pointer1, pointer3));
+        midPointer12.setOnTouchListener(new MidPointTouchListenerImpl(pointer1, pointer2));
+        midPointer34.setOnTouchListener(new MidPointTouchListenerImpl(pointer3, pointer4));
+        midPointer24.setOnTouchListener(new MidPointTouchListenerImpl(pointer2, pointer4));
+
+        super.invalidate();
+    }
+    
+    public void superInvalidate() {
+        super.invalidate();
+    }
 }