目前很多项目中都会用到“刮刮乐”这个功能点，处于此整理出了一套比较easy的实现方法。

在这里我主要用到了ImageMaskView这个类，下面来说说具体操作：

将项目中的Tools工具直接拖入到工程，ImageMaskView类作为VC的一个属性并遵循ImageMaskFilledDelegate的代理方法：

@interface ViewController ()<ImageMaskFilledDelegate>
@property(nonatomic, strong)ImageMaskView *baseImage;

图片的有两层，第一层为上面的覆盖层_baseImage，第二层为刮刮乐刮开后显示的图片层beforeImage：

UIImageView *beforeImage = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"image"]];
beforeImage.frame = CGRectMake(10, 60, self.view.frame.size.width-20, 100);
beforeImage.center = self.view.center;
[self.view addSubview:beforeImage];

beforeImage.layer.borderColor = [UIColor grayColor].CGColor;
beforeImage.layer.borderWidth = 1;


//创建ImageMaskView
_baseImage = [[ImageMaskView alloc] initWithImage:[UIImage imageNamed:@"base"]];
_baseImage.alpha = 1.0;
_baseImage.frame = CGRectMake(10, 60, self.view.frame.size.width-20, 100);
_baseImage.center = self.view.center;
[self.view addSubview:_baseImage];

实现基本UI后，设置画笔半径radius大小：

//设置画笔的半径
  _baseImage.radius = 10;

调用ImageMaskView的beginInteraction方法：

// Initialization code
self.userInteractionEnabled = YES;
self.backgroundColor = [UIColor clearColor];
self.imageMaskFilledDelegate = self.imageMaskFilledDelegate ? self.imageMaskFilledDelegate : nil;
self.radius = self.radius > 0 ? self.radius : 20;

// Initalize bitmap context
CGSize size = self.image.size;
self.colorSpace = CGColorSpaceCreateDeviceRGB();
self.imageContext = CGBitmapContextCreate(0,size.width,
                                          size.height,
                                          8,
                                          size.width*4,
                                          colorSpace,
                                          kCGImageAlphaPremultipliedLast    );
CGContextDrawImage(self.imageContext, CGRectMake(0, 0, size.width, size.height), self.image.CGImage);

int blendMode = kCGBlendModeClear;
CGContextSetBlendMode(self.imageContext, (CGBlendMode) blendMode);

tilesX = size.width / (2 * self.radius);
tilesY = size.height / (2 * self.radius);

self.maskedMatrix = [[Matrix alloc] initWithMax:MySizeMake(tilesX, tilesY)];
self.tilesFilled = 0;

最重要的是要要设置代理：

_baseImage.imageMaskFilledDelegate = self;

实现代理方法：

#pragma mark ImageMaskFilledDelegate
- (void) imageMaskView:(ImageMaskView *)maskView clearPercentDidChanged:(float)clearPercent{
if (clearPercent > 50) {
    [UIView animateWithDuration:2
                     animations:^{
                         _baseImage.userInteractionEnabled = NO;
                         _baseImage.alpha = 0;
                         _baseImage.imageMaskFilledDelegate = nil;
                     }
                     completion:^(BOOL finished) {
                     }];
  }
}

效果图：

刮开前

刮开中

GIF图片：

刮刮乐.gif

需要源码的，点击这里