比如,我想為UIView設定一個全屏的背景圖片,但是所用圖片太大,又因為這個UIView是根據螢幕大小動態生成的,這時就需要動態改變這個圖片的大小,使之能夠適應不同裝置.

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];