code: function Barcode2D() {
    this.width = 0;
    this.height = 0;
    this.background = '#FFF';
    this.modulecolor = '#000';
    this.type = 'PNG';
    this.leftoffset = 0;
    this.topoffset = 0;
    this.unitwidth = 0;
    this.unitheight = 0;
  }
docs: /*
  Basic constructor