UIImagePickerController的默認(rèn)比例是4：3，如果想要全屏的話，要對應(yīng)的設(shè)置transform

Swift

let screenSize = UIScreen.mainScreen().bounds.size
let aspectRatio:CGFloat = 4.0/3.0
let scale = screenSize.height/screenSize.width * aspectRatio
self.imagePikerViewController.cameraViewTransform = CGAffineTransformMakeScale(scale, scale);

Objective C

CGSize screenSize = [[UIScreen mainScreen] bounds].size;
float aspectRatio = 4.0/3.0;
float scale = screenSize.height/screenSize.width * aspectRatio;
self.imagePikerViewController.cameraViewTransform = CGAffineTransformMakeScale(scale, scale);

效果

Paste_Image.png