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Minecraft Random Icon

so its been what like 3 weeks. guess my one article a week is fallen behind a little :\

Anywhoo on to this little project. Minecraft servers have the ability to show a MOTD (Message of the day) and a 64*64 PX icon on the server selector page. A few servers show randomized MOTDs (2b2t + clones) but I am yet to come across one with a randomized icon. Sooooooooo let’s make it!

I have already made a MOTD randomizer in the past but it used the craftbukkit API so it was super easy. For this I need it to be a fabric mod so we will be using mixins. wooooooo…

Implementation

After a little but of CTRL clicking through the Minecraft code I found the following functions in the ServerMetadata class: getFavicon and getDescription. As the name implies these are the functions used to get the data to respond with when a server is pinged. Both return text (Description: Text, Favicon: String) so I was wondering how the image was stored, and it turns out its in base 64 encoding. So now that we know all that let’s work on the implementation.

The Motd

I started with the easy part: the MOTD. The motd options are stored in a text file that gets embedded in the jar. On mod init this file is read and added to a static variable.

public static final List<String> motds =
    new BufferedReader(new InputStreamReader(Objects.requireNonNull(
                           classLoader.getResourceAsStream("motd.txt"))))
        .lines()
        .toList();

Now for the mixin part. Although it’s not a good practice I used Overwrite because the function just returned one thing. In the new function it just picks a random MOTD to return. that’s it

@Mixin(ServerMetadata.class)
public class Motd {
  // SNIP //

  @Overwrite
  public @Nullable Text getDescription() {
    return Text.of(motds.get(rand.nextInt(0, motds.size())));
  }

  // SNIP //
}

The Favicon

This part turned out to be really quite difficult. The first step was loading images and this required having images. I took some of the Minecraft block textures and scaled them to the right size with a little ImageMagick, Magic.

Like before I wanted to embed them in the jar but as it turns out,,, java bad. I put the images in a folder and had it get the folder as a File and dynamically get and load the files within. This worked great until I put it in a JAR, in the JAR it was unable to get the folder as a file. After some duckduckgoing I found the only way to do this was to load the jar into memory, decompress it and get the files that way. That solution is kinda insane to I gave up on the whole dynamic loading thing and just made a huge array of all the file names to load. This worked perfectly and I just had to convert the image to a base64 string and store it in an array.

I ended coming up with this mess:

// Make an empty array
public static List<String> favs = new ArrayList<>();

static {
  // Loop through all image names
  for (String i : imageNames)
    try {
      // Read the image bytes
      ByteBuf byteBuf = Unpooled.buffer();
      BufferedImage img = ImageIO.read(new ByteArrayInputStream(
          Objects
              .requireNonNull(
                  classLoader.getResourceAsStream("favicon/" + i + ".png"))
              .readAllBytes()));
      ImageIO.write(img, "PNG", new ByteBufOutputStream(byteBuf));

      // Encode the image as Base64
      ByteBuffer byteBuffer = Base64.getEncoder().encode(byteBuf.nioBuffer());

      // Add image to array
      favs.add("data:image/png;base64," +
               StandardCharsets.UTF_8.decode(byteBuffer));
    } catch (IOException e) {
      e.printStackTrace();
    }
}

And finally the mixin to randomize the Favicons.

@Mixin(ServerMetadata.class)
public class Motd {
  // SNIP //

  @Overwrite
  @Nullable
  public String getFavicon() {
    return favs.get(rand.nextInt(0, favs.size()));
  }
}

Showcase

Conclusion

in conclusion java == bad,,, or something

This was such a small project that I don’t have it on git or anything. The images and text are built-in so it’s not configurable at all. If you want to use this just make your own mod and steal barrow some code from here. could also just message me here.

thats all