IOS 如何为UIView设置大小适宜的背景图片

比如,我想为UIView设置一个全屏的背景图片,但是所用图片太大,又因为这个UIView是根据屏幕大小动态生成的,这时就需要动态改变这个图片的大小,使之能够适应不同设备.

 

UIImage *img_m = [UIImage imageNamed:@"login1.jpg"];
    UIImage *img_a;
    CGFloat width = self.view.frame.size.width;
    CGFloat height = self.view.frame.size.height;
    
    UIGraphicsBeginImageContext(CGSizeMake(width, height));

    [img_m drawInRect:CGRectMake(0, 0, width, height)];
    img_a = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    self.upDownView.backgroundColor = [UIColor colorWithPatternImage:img_a];