C++ 如何从ImageMagick图像中获取c缓冲区

我正在使用ImageMagick的iPhone端口。我正在尝试循环动画gif的帧，并将每个帧转换为UIImage。我知道我可以使用NSData初始化UIImage，而我可以使用const void*初始化UIImage。那么如何获得图像的缓冲区和长度呢

代码如下：

    MagickReadImage(wand, filename);

        while(MagickHasNextImage(wand)) {
             Image *myImage = GetImageFromMagickWand(wand);
             //HELP ME PLEASE
             const void *myBuff =myImage->blob;  //guessing this is the right way to get the buffer?
             int myLength = ????? //no idea how to get the length
             NSData *myData = [[NSData alloc] initWithBytes:myBuff length:myLength];
             UIImage myImage = [[UIImage alloc] initWithData:myData]];
             MagickNextImage(wand);
    }

---

我现在有了解决办法：

    size_t my_size;
    unsigned char * my_image = MagickGetImageBlob(wand, &my_size);
    NSData * data = [[NSData alloc] initWithBytes:my_image length:my_size];
    free(my_image);

    UIImage * image = [[UIImage alloc] initWithData:data];