Write Animated GIF Image with Completion Block

gistfile1.m

+ (void)writeAnimatedGIFToPath:(NSURL*)path withImages:(NSArray*)images duration:(CGFloat)duration completionBlock:(dispatch_block_t)completionBlock;
{
  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    NSDictionary *fileProperties = @{
                                     (__bridge id)kCGImagePropertyGIFDictionary: @{
                                         (__bridge id)kCGImagePropertyGIFLoopCount: @0, // 0 means loop forever
                                         }
                                     };
    
    NSDictionary *frameProperties = @{
                                      (__bridge id)kCGImagePropertyGIFDictionary: @{
                                          (__bridge id)kCGImagePropertyGIFDelayTime:@(duration / (CGFloat)[images count]),
                                          }
                                      };
    
    CGImageDestinationRef destination = CGImageDestinationCreateWithURL((__bridge CFURLRef)path, kUTTypeGIF, [images count], NULL);
    CGImageDestinationSetProperties(destination, (__bridge CFDictionaryRef)fileProperties);
    
    for (id image in images) {
      @autoreleasepool {
        if ([image isKindOfClass:[UIImage class]]) {
          CGImageDestinationAddImage(destination, [image CGImage], (__bridge CFDictionaryRef)frameProperties);
        } else {
          CGImageDestinationAddImage(destination, (__bridge CGImageRef)image, (__bridge CFDictionaryRef)frameProperties);
        }
      }
    }
    
    if (!CGImageDestinationFinalize(destination)) {
      NSLog(@"failed to finalize image destination");
    }
    CFRelease(destination);
    
    NSLog(@"url=%@", path);
    
    if (completionBlock) {
      dispatch_async(dispatch_get_main_queue(), completionBlock);
    }
  });
}