#pragma mark -- 解析 DGIF

-(void)gifWithUrl:(NSURL *)url

               returnData:(void(^)(NSArray<UIImage *> * imageArray,

                                   NSArray<NSNumber *>*timeArray,

                                   CGFloat totalTime,

                                   NSArray<NSNumber *>* widths,

                                   NSArray<NSNumber *>* heights))dataBlock

{

    //通过文件的 url 来将 gif 文件读取为图片数据引用

    CGImageSourceRef source = CGImageSourceCreateWithURL((CFURLRef)url,NULL);

    //获取 gif 文件中的图片个数

    size_t count = CGImageSourceGetCount(source);

    //定义一个变量记录 gif 播放一轮的时间

    float allTime = ;

    //存放所有图片

    NSMutableArray *imageArray = [NSMutableArray array];

    //存放每一帧播放的时间

    NSMutableArray *timeArray = [NSMutableArray array];

    //存放每张图片的宽度（一般在一个 gif 文件中，所有文件的尺寸都一样）

    NSMutableArray *widthArray = [NSMutableArray array];

    //存放每张图片的高度

    NSMutableArray * heightArray = [NSMutableArray array];

    //遍历

    for(size_t i = ;i < count; i++){

    //获取图片信息

        CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);

        [imageArray addObject:(__bridge UIImage *)(image)];

        CGImageRelease(image);

        //获取图片信息

        NSDictionary *info = (__bridge NSDictionary *)CGImageSourceCopyPropertiesAtIndex(source, i, NULL);

        NSLog(@"%@",info);

        CGFloat width = [[info objectForKey:(__bridge NSString *)kCGImagePropertyPixelWidth]floatValue];

        CGFloat height = [[info objectForKey:(__bridge NSString *)kCGImagePropertyPixelHeight]floatValue];

        [widthArray addObject:[NSNumber numberWithFloat:width]];

        [heightArray addObject:[NSNumber numberWithFloat:height]];

        NSDictionary *timeDic = [info objectForKey:(__bridge NSString *)kCGImagePropertyGIFDictionary];

        CGFloat time = [[timeDic objectForKey:(__bridge NSString *)kCGImagePropertyGIFDelayTime]floatValue];

        allTime += time;

        [timeArray addObject:[NSNumber numberWithFloat:time]];

    }

    dataBlock(imageArray,timeArray,allTime,widthArray,heightArray);

}

• kCAMediaTimingFunctionLinear（线性）：匀速，给你一个相对静态的感觉
• kCAMediaTimingFunctionEaseIn（渐进）：动画缓慢进入，然后加速离开
• kCAMediaTimingFunctionEaseOut（渐出）：动画全速进入，然后减速的到达目的地
• kCAMediaTimingFunctionEaseInEaseOut（渐进渐出）：动画缓慢的进入，中间加速，然后减速的到达目的地。这个是默认的动画行为

#pragma mark -- 加载 GIF

- (void)cc_setImage:(NSURL *)imageUrl {

    __weak id _self = self;

    [self gifWithUrl:imageUrl returnData:^(NSArray<UIImage *> *imageArray, NSArray<NSNumber *> *timeArray, CGFloat totalTime, NSArray<NSNumber *> *widths, NSArray<NSNumber *> *heights) {

        CAKeyframeAnimation *animation = [CAKeyframeAnimation animationWithKeyPath:@"contents"];

        NSMutableArray * times = [[NSMutableArray alloc]init];

        float currentTime = ;

        //设置每一帧的时间占比

        for (int i = ; i < imageArray.count; i++) {

            [times addObject:[NSNumber numberWithFloat:currentTime/totalTime]];

            currentTime += [timeArray[i] floatValue];

        }

        [animation setKeyTimes:times];

        [animation setValues:imageArray];

        [animation setTimingFunction:[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut]];

        //设置循环

        animation.repeatCount= MAXFLOAT;

        //设置播放总时长

        animation.duration = totalTime;

        //Layer层添加

        [[(UIImageView *)_self layer]addAnimation:animation forKey:@"gifAnimation"];

    }];

}