node-boleto/lib/barcode.js

exports.binaryRepresentationForBarcodeData = function(barcodeData) {
  var digits = {
	0: "00110",
	1: "10001",
	2: "01001",
	3: "11000",
	4: "00101",
	5: "10100",
	6: "01100",
	7: "00011",
	8: "10010",
	9: "01010"
  };

  if (barcodeData.length % 2 != 0) {
	barcodeData = "0" + barcodeData;
  }

  var binaryDigits = "0000";
  // Start of barcode
  for (var i = 0; i < barcodeData.length; i += 2) {
	var digit1 = digits[parseInt(barcodeData[i])];
	var digit2 = digits[parseInt(barcodeData[i + 1])];

	for (var j = 0; j < digit1.length; j++) {
	  binaryDigits += digit1[j] + digit2[j];
	}
  }

  // End of barcode
  binaryDigits += "1000";

  return binaryDigits;
}

// Convert a value to a little endian hexadecimal value
exports._getLittleEndianHex = function(value) {
  var result = [];

  for (var bytes = 4; bytes > 0; bytes--) {
	result.push(String.fromCharCode(value & 0xff));
	value >>= 0x8;
  }

  return result.join('');
}

exports._bmpHeader = function(width, height) {
  var numFileBytes = exports._getLittleEndianHex(width * height);
  width = exports._getLittleEndianHex(width);
  height = exports._getLittleEndianHex(height);
  
  return 'BM' + // Signature
	numFileBytes + // size of the file (bytes)*
	'\x00\x00' + // reserved
	'\x00\x00' + // reserved
	'\x36\x00\x00\x00' + // offset of where BMP data lives (54 bytes)
	'\x28\x00\x00\x00' + // number of remaining bytes in header from here (40 bytes)
	width + // the width of the bitmap in pixels*
	height + // the height of the bitmap in pixels*
	'\x01\x00' + // the number of color planes (1)
	'\x20\x00' + // 32 bits / pixel
	'\x00\x00\x00\x00' + // No compression (0)
	'\x00\x00\x00\x00' + // size of the BMP data (bytes)*
	'\x13\x0B\x00\x00' + // 2835 pixels/meter - horizontal resolution
	'\x13\x0B\x00\x00' + // 2835 pixels/meter - the vertical resolution
	'\x00\x00\x00\x00' + // Number of colors in the palette (keep 0 for 32-bit)
	'\x00\x00\x00\x00'; // 0 important colors (means all colors are important)
}

exports.bmpLineForBarcodeData = function(barcodeData) {
  var binaryRepresentation = exports.binaryRepresentationForBarcodeData(barcodeData);

  var bmpData = new Array();
  var black = true;
  var offset = 0;

  for(var i = 0; i < binaryRepresentation.length; i++) {
	var digit = binaryRepresentation[i];
	var color = black ? String.fromCharCode(0, 0, 0, 0) : String.fromCharCode(255, 255, 255, 0);
	var pixelsToDraw = (digit == "0") ? 1 : 3;

	for(var j = 0; j < pixelsToDraw; j++) {
	  bmpData[offset++] = color;
	}

	black = !black;
  }

  var bmpHeader = exports._bmpHeader(offset - 1, 1);
  var bmpBuffer = new Buffer(bmpHeader + bmpData.join(""), 'binary');
  return bmpBuffer.toString('base64');
}