Get PNG header information from an image (width, height, bit depth, and color type)

pngHeaderInformation.js

var fs = require('fs');

fs.readFile('test.png', function (err, data) {
  var pngHeader = new Buffer([137, 80, 78, 71, 13, 10, 26, 10]);
  var header = data.slice(0, 8);
  if(header.compare(pngHeader) != 0) {
    console.log('Invalid png file header!')
    process.exit();
  }
  var fileHeader = {
    "width" : data.readInt32BE(16),
    "height" : data.readInt32BE(20),
    "bitDepth" : data.readInt32BE(24),
    "colorType" : data.readInt32BE(28)
  }
  console.log(fileHeader);
});