截取当前屏幕

#import <QuartzCore/QuartzCore.h>
@property (retain, nonatomic) IBOutlet UIImageView *imageView;

-(UIImage*)getShot
{
    UIGraphicsBeginImageContext(CGSizeMake(320, 460));
    [imageView.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return viewImage;
}