constructor(mainFile, overviewFiles) {
    super();
    this.mainFile = mainFile;
    this.overviewFiles = overviewFiles;
    this.imageFiles = [mainFile].concat(overviewFiles);

    this.fileDirectoriesPerFile = null;
    this.fileDirectoriesPerFileParsing = null;
    this.imageCount = null;
  }
Construct a new MultiGeoTIFF from a main and several overview files.
@param {GeoTIFF} mainFile The main GeoTIFF file.
@param {GeoTIFF[]} overviewFiles An array of overview files.