constructor(fileDirectory, rawFileDirectory, geoKeyDirectory, nextIFDByteOffset) {
    this.fileDirectory = fileDirectory;
    this.rawFileDirectory = rawFileDirectory;
    this.geoKeyDirectory = geoKeyDirectory;
    this.nextIFDByteOffset = nextIFDByteOffset;
  }
Create an ImageFileDirectory.
@param {object} fileDirectory the file directory, mapping tag names to values
@param {Map} rawFileDirectory the raw file directory, mapping tag IDs to values
@param {object} geoKeyDirectory the geo key directory, mapping geo key names to values
@param {number} nextIFDByteOffset the byte offset to the next IFD