Use the 9-patch editor

Inside Sony’s Theme Creator is a dedicated 9-patch editor, allowing you to create bitmap images that automatically resize to fit contents within the view and size of screen. You are able to use the 9-patch editor to select parts of an image to be scaled horizontally and vertically, for use in your theme.

You can find out more about using 9-patches and specifically the 9-patch editor in the Theme Creator tool by watching this tutorial video.