目前很多項目中都會用到“刮刮樂”這個功能點，處于此整理出了一套比較easy的實現方法。

在這里我主要用到了ImageMaskView這個類，下面來說說具體操作：

將項目中的Tools工具直接拖入到工程，ImageMaskView類作為VC的一個屬性并遵循ImageMaskFilledDelegate的代理方法：

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

圖片的有兩層，第一層為上面的覆蓋層_baseImage，第二層為刮刮樂刮開后顯示的圖片層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;


//創建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];

實現基本UI后，設置畫筆半徑radius大小：

//設置畫筆的半徑
  _baseImage.radius = 10;

調用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;

最重要的是要要設置代理：

_baseImage.imageMaskFilledDelegate = self;

實現代理方法：

#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) {
                     }];
  }
}

效果圖：

刮開前

刮開中

GIF圖片：

刮刮樂.gif

需要源碼的，點擊這里