GIF动画加载

#pragma mark - Gif
/**
 *  播放动画
 *
 *  @param data 源文件（图片源）
 *
 *  @return
 */
+ (UIImage *)animatedGIFWithData:(NSData *)data {
    if (!data) {
        return nil;
    }
    
    // 加载所有图片
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)data, NULL);
    // 图片数量
    size_t count = CGImageSourceGetCount(source);
    
    UIImage *animatedImage;
    // 只有一张，直接加载
    if (count <= 1) {
        animatedImage = [[UIImage alloc] initWithData:data];
    }
    // 多张图片，循环播放
    else {
        NSMutableArray *images = [NSMutableArray array];
        
        NSTimeInterval duration = 0.0f;
        
        for (size_t i = 0; i < count; i++) {
            
            CGImageRef image = CGImageSourceCreateImageAtIndex(source, i, NULL);
            // 图片播放时间累加
            duration += [self frameDurationAtIndex:i source:source];
            
            [images addObject:[UIImage imageWithCGImage:image
                                                  scale:[UIScreen mainScreen].scale
                                            orientation:UIImageOrientationUp]];
            
            CGImageRelease(image);
        }
        
        if (!duration) {
            duration = (1.0f / 10.0f) * count;
        }
        // 加载动画图片，指定动画播放时间
        animatedImage = [UIImage animatedImageWithImages:images duration:duration];
    }
    
    CFRelease(source);
    
    return animatedImage;
}

/**
 *  计算动画中每一张图片的播放时间
 *
 *  @param index  图片索引
 *  @param source 图片组
 *
 *  @return  播放时间
 */
+ (float)frameDurationAtIndex:(NSUInteger)index source:(CGImageSourceRef)source {
    float frameDuration = 0.1f;
    
    // 字典转换
    CFDictionaryRef cfFrameProperties = CGImageSourceCopyPropertiesAtIndex(source, index, nil);
    NSDictionary *frameProperties = (__bridge NSDictionary *)cfFrameProperties;
    NSDictionary *gifProperties = frameProperties[(NSString *)kCGImagePropertyGIFDictionary];
    
    // 如果有延迟时间
    NSNumber *delayTimeUnclampedProp = gifProperties[(NSString *)kCGImagePropertyGIFUnclampedDelayTime];
    if (delayTimeUnclampedProp) {
        frameDuration = [delayTimeUnclampedProp floatValue];
    }
    // 否则就获取播放下一张图片需要等待的时间
    else {
        
        NSNumber *delayTimeProp = gifProperties[(NSString *)kCGImagePropertyGIFDelayTime];
        if (delayTimeProp) {
            frameDuration = [delayTimeProp floatValue];
        }
    }

    // 设置最小值
    if (frameDuration < 0.011f) {
        frameDuration = 0.100f;
    }
    
    CFRelease(cfFrameProperties);
    return frameDuration;
}

/**
 *  播放gif动画
 *
 *  @param name 文件名
 *
 *  @return
 */
+ (UIImage *)animatedGIFNamed:(NSString *)name {
    CGFloat scale = [UIScreen mainScreen].scale;
    
    // 视网膜屏，可能要加载高清图
    if (scale > 1.0f) {
        // 文件名1
        NSString *retinaPath = [[NSBundle mainBundle] pathForResource:[name stringByAppendingString:@"@2x"] ofType:@"gif"];
        
        NSData *data = [NSData dataWithContentsOfFile:retinaPath];
        
        if (data) {
            return [UIImage animatedGIFWithData:data];
        }
        
        // 文件名2
        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];
        
        data = [NSData dataWithContentsOfFile:path];
        
        if (data) {
            return [UIImage animatedGIFWithData:data];
        }
        
        return [UIImage imageNamed:name];
    }
    // 普通屏幕
    else {
        NSString *path = [[NSBundle mainBundle] pathForResource:name ofType:@"gif"];
        
        NSData *data = [NSData dataWithContentsOfFile:path];
        
        if (data) {
            return [UIImage animatedGIFWithData:data];
        }
        
        return [UIImage imageNamed:name];
    }
}

/**
 *  缩放动画
 *
 *  @param size 大小
 *
 *  @return  
 */
- (UIImage *)animatedImageByScalingAndCroppingToSize:(CGSize)size {
    if (CGSizeEqualToSize(self.size, size) || CGSizeEqualToSize(size, CGSizeZero)) {
        return self;
    }
    
    CGSize scaledSize = size;
    CGPoint thumbnailPoint = CGPointZero;
    
    CGFloat widthFactor = size.width / self.size.width;
    CGFloat heightFactor = size.height / self.size.height;
    CGFloat scaleFactor = (widthFactor > heightFactor) ? widthFactor : heightFactor;
    scaledSize.width = self.size.width * scaleFactor;
    scaledSize.height = self.size.height * scaleFactor;
    
    if (widthFactor > heightFactor) {
        thumbnailPoint.y = (size.height - scaledSize.height) * 0.5;
    }
    else if (widthFactor < heightFactor) {
        thumbnailPoint.x = (size.width - scaledSize.width) * 0.5;
    }
    
    NSMutableArray *scaledImages = [NSMutableArray array];
    
    // 重绘制图片
    UIGraphicsBeginImageContextWithOptions(size, NO, 0.0);
    for (UIImage *image in self.images) {
        [image drawInRect:CGRectMake(thumbnailPoint.x, thumbnailPoint.y, scaledSize.width, scaledSize.height)];
        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
        
        [scaledImages addObject:newImage];
    }
    
    UIGraphicsEndImageContext();
    
    return [UIImage animatedImageWithImages:scaledImages duration:self.duration];
}