iOS 四周半透明中间圆形全透明View制作

- (UIImage *)getImage{

    UIGraphicsBeginImageContextWithOptions([UIScreen mainScreen].bounds.size, NO, 1.0);

    CGContextRef con = UIGraphicsGetCurrentContext();

    

    CGContextSetFillColorWithColor(con, [UIColor lightGrayColor].CGColor);//背景色

    CGContextFillRect(con, [UIScreen mainScreen].bounds);

    

    CGContextAddEllipseInRect(con, CGRectMake(50, 100, 200, 200));

    CGContextSetBlendMode(con, kCGBlendModeClear);

    CGContextFillPath(con);

    

    UIImage *ima = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

    

    return ima;

    

}

- (void)addImage{

    UIImageView *imageV = [[UIImageView alloc]initWithFrame:[UIScreen mainScreen].bounds];

    imageV.image = [self getImage];

    imageV.alpha = 0.5;

    [self.view addSubview:imageV];

}