Unable to get a valid stream when converting from gif to apng

[Kaoticz]

I'm having trouble converting a stream from a gif file into a stream of an apng file.
I have the following method:

private static Stream GetAPngStreamAsync(Stream gifStream)
{
    using var imageCollection = new MagickImageCollection(gifStream, MagickFormat.Gif);
    var result = new MemoryStream();

    imageCollection.Write(result, MagickFormat.APng);

    return result;
}

Then I get the resulting stream and save it to a file using File.WriteAllBytesAsync.

using var processedStream = GetAPngStreamAsync(stream);
var buffer = new byte[processedStream.Length];

processedStream.Write(buffer);
await File.WriteAllBytesAsync("/home/user/Pictures/sample.png", buffer);

However, this always generates an invalid file that no image handling program can open.

But if I write to a file directly from MagickImageCollection, as in

imageCollection.Write("/home/user/Pictures/sample.png", MagickFormat.APng);

Then I get a perfectly functional file.

For my purposes though, I really need a valid stream and I'd like to avoid an I/O operation to write a new file, then read back from it.
It's very likely that I'm doing something silly here. Can I get some tips on how to generate a valid apng stream?

Also, this is unrelated, but how can I accelerate/slow down the animation in the resulting apng?

[dlemstra]

You will need to reset the position of the stream? You might also be worth to consider using imageCollection.ToByteArray(MagickFormat.APng) instead when you want to change the image into a byte array?

[Kaoticz]

That was it! ToByteArray worked flawlessly, thanks!

Now to seal the deal, how can I change the animation speed of the resulting apng?
I see that IMagickImage<T> has an AnimationDelay property, but it seems to only affect how long it takes for the whole animation to play again, not the speed which the animation frames are played.