HID controller for WoW

index.js

// -----------------------------------------------------------------------------
// Screenshot
// -----------------------------------------------------------------------------

const exec = require("child_process").exec;
const Jimp = require("jimp");

function tempPath() {
  return "/tmp/healthbar-screenshot.png";
}

const dimensions = [1009, 893, 240, 1];

async function captureScreenshot() {
  const filepath = tempPath();
  const command = [
    "screencapture", "-x", "-R", dimensions.join(), "-t", "png", filepath
  ].join(" ");

  return new Promise((resolve, reject) => {
    exec(command, (err => {
      if (err) {
        reject(err);
      }
      resolve();
    }))
  });
}

function kindaEquals(a, b) {
  return Math.abs(a - b) < 5
}

function coloursEqual(a, b) {
  return kindaEquals(a.r, b.r) && kindaEquals(a.g, b.g) && kindaEquals(a.b, b.b);
}

function findRatio(image, healthy) {
  const length = image.getWidth();
  let ratio = 0;
  for(let x = 0; x < length; x++) {
    if (coloursEqual(healthy, Jimp.intToRGBA(image.getPixelColor(x, 0)))) {
      ratio++;
    }
  }

  return ratio / length;
}

async function analysePicture() {
  const filepath = tempPath();
  const image = await Jimp.read(filepath);

  const health = Jimp.intToRGBA(image.getPixelColor(0, 0));

  return findRatio(image, health);
}

// -----------------------------------------------------------------------------
// Keyboard
// -----------------------------------------------------------------------------

const HID = require("node-hid");

const VENDOR_ID = 0x3434;
const PRODUCT_ID = 0x0311;

const COMMAND_START = 0x00;
const BACKLIGHT_CONFIG_SET_VALUE = 0x07;
const QMK_RGBLIGHT = 0x83;

function padArray(input) {
  const result = new Array(33).fill(0);
  input.forEach((b, i) => result[i] = b);
  return result;
}

const green = 64
const red = 0;

function lerp(a, b, t) {
  return a + (b - a) * t;
}

function connectDevice() {
  const device = new HID.HID(VENDOR_ID, PRODUCT_ID);
  return device
}

function setColour(device, ratio) {
  const hue = lerp(red, green, ratio);
  try {
    const command = [COMMAND_START, BACKLIGHT_CONFIG_SET_VALUE, QMK_RGBLIGHT, hue, 0xff];
    const padded = padArray(command);

    device.write(padded.slice(0, padded.length - 1))
  } catch(err) {
    console.error(err);
  }
}

// -----------------------------------------------------------------------------
// Entrypoint
// -----------------------------------------------------------------------------

async function iteration(device) {

  await captureScreenshot();
  const ratio = await analysePicture();
  setColour(device, ratio)
}

function run() {
  const device = connectDevice();

  process.on("SIGINT", () => {
    device.close();
    process.exit();
  });


  setInterval(async () => {
    await iteration(device);
  }, 1000)
}

run();