Node - Image to DDS

dds.ts

//@ts-ignore
import dxt from 'dxt-js';
import { createCanvas, loadImage } from 'canvas';
import fs from 'fs';
import { Buffer } from 'buffer';

(async () => {
  
  const image = await loadImage('${__dirname}/input.jpg');
  const { width, height } = image;
  const canvas = createCanvas(width, height);
  const ctx = canvas.getContext('2d')
  ctx.drawImage(image, 0, 0);
  ctx.scale(1, -1);

  // need to check this is actually correct
  const pitch = Math.floor(((width * height) * 4 + 7) / 8);

  let offset = 0;

  const headerBuffer = Buffer.allocUnsafe(128);
  headerBuffer.write('DDS ', offset++ * 4, 'ascii');   // [0] magic
  headerBuffer.writeUInt32LE(124, offset++ * 4);       // [1] header size
  headerBuffer.writeUInt32LE(528391, offset++ * 4);    // [2] flags
  headerBuffer.writeUInt32LE(height, offset++ * 4);    // [3] height
  headerBuffer.writeUInt32LE(width, offset++ * 4);     // [4] width
  headerBuffer.writeUInt32LE(pitch, offset++ * 4);     // [5] pitch
  headerBuffer.writeUInt32LE(0, offset++ * 4);         // [6] depth
  headerBuffer.writeUInt32LE(1, offset++ * 4);         // [7] mipMapCount
  for (let i = 0; i < 11; i++) {
    headerBuffer.writeUInt32LE(0, offset++ * 4);         // [8 - 18] reserved
  }
  headerBuffer.writeUInt32LE(32, offset++ * 4);        // [19] pf size
  headerBuffer.writeUInt32LE(5, offset++ * 4);         // [20] pf flags
  headerBuffer.write('DXT1', offset++ * 4, 'ascii');   // [21] pf fourcc
  headerBuffer.writeUInt32LE(32, offset++ * 4);        // [22] pf rgbbitcount
  headerBuffer.writeUInt32LE(0xFF000000, offset++ * 4);// [23] pf rbitmask
  headerBuffer.writeUInt32LE(0xFF0000, offset++ * 4);  // [24] pf gbitmask
  headerBuffer.writeUInt32LE(0xFF00, offset++ * 4);    // [25] pf bbitmask
  headerBuffer.writeUInt32LE(0xFF, offset++ * 4);      // [26] pf abitmask
  headerBuffer.writeUInt32LE(0x1000, offset++ * 4);    // [27] caps
  headerBuffer.writeUInt32LE(0, offset++ * 4);         // [28] caps2
  headerBuffer.writeUInt32LE(0, offset++ * 4);         // [29] caps3
  headerBuffer.writeUInt32LE(0, offset++ * 4);         // [30] reserved2

  let flags = dxt.flags.DXT1 | dxt.flags.ColourIterativeClusterFit | dxt.flags.ColourMetricPerceptual;

  const compressed = dxt.compress(
    ctx.getImageData(0, 0, width, height).data,
    width,
    height,
    flags
  );
  

  let finalBuffer = Buffer.concat([
    headerBuffer,
    Buffer.from(compressed)
  ]);
  
  fs.writeFileSync(`${__dirname}/output.dds`, finalBuffer);
})();