First rule before to start how to learn to theme your device :
Always make a backup of the files you are about to edit or do a nandroid backup.
If anything goes wrong you will get a bootloop.
☺ TOOLS you must have ☺
1. PHOTOSHOP / GIMP http://www.gimp.org/downloads
or a good alternative for those who are rookies in Adobe products : PAINT.NET http://www.paint.net
or any other Graphics editor you like to use of your choice.
2. DRAW 9-PATCH http://developer.android.com/sdk/index.html
You will find it in your SDK starter package ( android sdk/tools )
The Draw 9-patch tool allows you to easily create a NinePatch graphic using a WYSIWYG editor.
3. xUltimate-d9pc.exe http://lmgtfy.com/?q=xUltimate-d9pc
Basically you will need to compile the edited 9.png to Draw9Patch Compiler
Now let's play with your pics in the graphic editor of your choice :
your 9.png's files would be in <drawable/drawable-hdpi> folder' apk
When you are done editing your image,
you can open it in the draw9patch tool to verify that it stretches properly.
Here is the most important part of the 9.png creation.
You need to define 2 parts :
* Stretch part ( always left and up side )
* Content part ( always right and bottom side )
When you are done stretching your image,
you can open it in the 9.png compiler tool to compile it properly.
you notice the 1pixel border created for the stretcheable 9.png
Place your files in example1/drawable-hdpi
Execute the xUltimate-d9pc.exe
If you defined properly your 9.png,
you must find no errors and you can hear a "peeep"
Compiled ready files are in /Done folder
When you are done compiling your image,
you can see that the 1pixel border disappeared.
Use 7-ZIP http://www.7-zip.org
(an open source file archiver with a high compression ratio)
to drag your files into the apk !
Source : androidbyyorzua
Congatulations, you can enjoy your work