Zoom Image View on pull down

问题:

I have a view with structure like

 <ScrollView>
    <RelativeLayout>
       <ImageView>
       <LinearLayout>
              <!-- Here I show some details in textview-->
       </LinearLayout>
    </RelativeLayout>
</ScrollView>

Now I what i want is when i scroll down or drag down the linear layout I want to increase the ImageView size with the scroll down amount and when I release the drag/scroll it should become as initial size.This is done in Path android app. I need idea to achieve this, please help if anybody did this.