The use of 9 patch images for Android development is to help keep the app lower in the size. We can use 9 patch images for the buttons & backgrounds.
9patch image works like the scalable Graphic in the android & we can define the scalable area of the image. It has a slightly different approach in creating the 9patch images.
Scalable Area: Scalable area defines the area which is going to be scaled as per the content. The black patch to the Left & Top side of the image defines vertical & horizontal scaling area […]