background image problem

i have an image sized 768X1024 and when i set the background image to a view, at the bottom it displays the white color (20pixel).Eventhough I incereses the image size 768X1044 it repeats the s开发者_如何学编程ame.Please help me.

Make sure that the position is set to CGPointMake(0,0), with

[theImage setPosition:CGPointMake(0,0)];

It's probably just positioned up by 20 pixels.