maskView配合带alpha通道图片

maskView配合带alpha通道图片

1.比CAGradientLayer高效
2.可以加载多张图片，并实现动画特效

    UIImageView  *backgroundView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
    backgroundView.image = [UIImage imageNamed:@"background"];
    backgroundView.center = self.view.center;
    [self.view addSubview:backgroundView];


    UIImageView  *baseView = [[UIImageView alloc] initWithFrame:backgroundView.frame];
    baseView.image = [UIImage imageNamed:@"base"];
    [self.view addSubview:baseView];

    //创建maskView作为容器
    UIView *mask = [[UIView alloc] initWithFrame:baseView.bounds];
    baseView.maskView = mask;

    //maskView中的subView1
    UIImageView *picOne = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 100, 400)];
    picOne.image = [UIImage imageNamed:@"1"];
    [mask addSubview:picOne];

    //maskView中的subView2
    UIImageView *picTwo = [[UIImageView alloc] initWithFrame:CGRectMake(0, -200, 100, 400)];
    picTwo.image = [UIImage imageNamed:@"2"];
    [mask addSubview:picTwo];

    [UIView animateWithDuration:2.f animations:^{
        CGRect oneFrame = picOne.frame;
        oneFrame.origin.y -= 400;
        picOne.frame = oneFrame;


        CGRect twoFrame = picTwo.frame;
        twoFrame.origin.y -= 400;
        picTwo.frame = twoFrame;

    }];

github上开源的代码可查看