毛玻璃效果

UIVisualEffectView *bgView = [[UIVisualEffectView alloc] initWithEffect:[UIBlurEffect effectWithStyle:UIBlurEffectStyleLight]]; bgView.alpha = 0.9f;
 bgView.frame = CGRectMake(0, 0, WIDTH, HEIGHT);
 bgView.layer.cornerRadius = BALL_RADIUS / 2;
 bgView.clipsToBounds = YES; 
[self addSubview:bgView];