iOS基础-小Demo--刮开涂层(刮刮乐效果)

蛾儿雪柳黄金缕,笑语盈盈暗香去!<波克比>

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总结一个小的Demo,先看效果图.

刮开涂层效果.gif

1. 设置刮开后,显示的文字Label

UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(7, 50, 400, 400)];
label.text = @"离思五首\n元稹\n曾经沧海难为水,\n除却巫山不是云!\n取次花丛懒回顾,\n半缘修道半缘君!\n";
label.numberOfLines = 0;
label.backgroundColor = [UIColor colorWithRed:(arc4random()%173)/346.0 + 0.5 green:(arc4random()%173)/346.0 + 0.5 blue:(arc4random()%173)/346.0 + 0.5 alpha: 1];
label.font = [UIFont systemFontOfSize:30];
label.textAlignment = NSTextAlignmentCenter;
[self.view addSubview:label];

2. 设置遮挡在外面的Image
>```obj
self.imageView = [[UIImageView alloc]initWithFrame:CGRectMake(7, 50, 400, 400)];
    self.imageView.image = [UIImage imageNamed:@"可达鸭"];
    [self.view addSubview:self.imageView ];```
3. 在touchesMoved方法里面实现操作
>```obj
`- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
    // 触摸任意位置
    UITouch *touch = touches.anyObject;
    // 触摸位置在图片上的坐标
    CGPoint cententPoint = [touch locationInView:self.imageView];
    // 设置清除点的大小
    CGRect  rect = CGRectMake(cententPoint.x, cententPoint.y, 20, 20);
    // 默认是去创建一个透明的视图
UIGraphicsBeginImageContextWithOptions(self.imageView.bounds.size, NO, 0);  
    // 获取上下文(画板)
    CGContextRef ref = UIGraphicsGetCurrentContext();
       // 把imageView的layer映射到上下文中
    [self.imageView.layer renderInContext:ref];
    // 清除划过的区域
    CGContextClearRect(ref, rect);  
    // 获取图片
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    // 结束图片的画板, (意味着图片在上下文中消失)
    UIGraphicsEndImageContext();
    self.imageView.image = image;```