UIImageView图片拉伸问题

让UIImageView内的图片达到以短边为准居中铺开

    [imageView setContentScaleFactor:[[UIScreen mainScreen] scale]];
    imageView.contentMode =  UIViewContentModeScaleAspectFill;
    imageView.autoresizingMask = UIViewAutoresizingFlexibleHeight;
    imageView.clipsToBounds  = YES;