Android NAND img file Unpack and Repack

[mohammadfa91]

Hello can anyone introduce me a way to Unpack and Repack img files? my target img file is
"A13 Android NAND image with LCD 7" 800x480 and touchscreen"

The most effective way i found is this topic for Unpack, but i can't Repack that.
http://www.techknow.me/forum/index.php?topic=1679.msg14594#msg14594