I am going to create a theme and wanna set a 640x960 image (of course for IPh4/4s) as the springboard background image. I put the image under my xxx.theme folder and name it as wallpaper.png
Unfortunately, only part of the image (should be the top left hand part) showing on the screen and the left is out side the screen?
So how can I fix it?

ps. 640x960 image as lockscreen BG is ok