如何更改ZBar读卡器的框架？

Ok, so I'm using the ZBar SDK to scan barcodes in my iPhone app. I've successfully implemented the sample code, but now I want to change the frame of the scanner view (i.e: To half the screen size). I've tried setting the frame of the reader's view in viewDidLoad, but it resizes itself. I know this is going to be one of those really simple things I just missed, but any help would be much appreciated. Cheers. Ok, so I'm using the ZBar SDK to scan barcodes