Simple script to get width and height from image.

get-wh-jpg.js

const fs = require('fs');

fs.readFile('me.jpg', (err, data) => {
  if (err) throw err;

  let buf = Buffer.from(data).slice(4);

  while(buf.length) {
    const i = buf.readUInt16BE(0);
    next = buf[i + 1];

    if (next === 0xC0 || next === 0xC1 || next === 0xC2) {
        const width = buf.readUInt16BE(i + 7);
        const height = buf.readUInt16BE(i + 5);
        console.log(`${width}x${height}`);
    }

    buf = buf.slice(i + 2);
  }
});