iOS图片自适应屏幕 截取

/////// 自适应屏幕
_imageViewPics.contentMode = UIViewContentModeScaleAspectFit;
        _imageViewPics.autoresizesSubviews = YES;
        _imageViewPics.autoresizingMask =
        UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleHeight | UIViewAutoresizingFlexibleWidth;
         
         
 
///图片 截取
            _imageViewPic.clipsToBounds = YES;
            _imageViewPic.contentMode = UIViewContentModeCenter;