Function parseMetaData

js/load-image-meta.js:75–184

* Parses image metadata and calls the callback with an object argument * with the following property: * - imageHead: The complete image head as ArrayBuffer * The options argument accepts an object and supports the following * properties: * - maxMetaDataSize: Defines the maximum number

(file, callback, options, data)

   * @returns {Promise<object>|undefined} Returns Promise if no callback given.
   */
  function parseMetaData(file, callback, options, data) {
    var that = this
    /**
     * Promise executor
     *
     * @param {Function} resolve Resolution function
     * @param {Function} reject Rejection function
     * @returns {undefined} Undefined
     */
    function executor(resolve, reject) {
      if (
        !(
          global.DataView &&
          blobSlice &&
          file &&
          file.size >= 12 &&
          file.type === 'image/jpeg'
        )
      ) {
        // Nothing to parse
        return resolve(data)
      }
      // 256 KiB should contain all EXIF/ICC/IPTC segments:
      var maxMetaDataSize = options.maxMetaDataSize || 262144
      if (
        !loadImage.readFile(
          blobSlice.call(file, 0, maxMetaDataSize),
          function (buffer) {
            // Note on endianness:
            // Since the marker and length bytes in JPEG files are always
            // stored in big endian order, we can leave the endian parameter
            // of the DataView methods undefined, defaulting to big endian.
            var dataView = new DataView(buffer)
            // Check for the JPEG marker (0xffd8):
            if (dataView.getUint16(0) !== 0xffd8) {
              return reject(
                new Error('Invalid JPEG file: Missing JPEG marker.')
              )
            }
            var offset = 2
            var maxOffset = dataView.byteLength - 4
            var headLength = offset
            var markerBytes
            var markerLength
            var parsers
            var i
            while (offset < maxOffset) {
              markerBytes = dataView.getUint16(offset)
              // Search for APPn (0xffeN) and COM (0xfffe) markers,
              // which contain application-specific metadata like
              // Exif, ICC and IPTC data and text comments:
              if (
                (markerBytes >= 0xffe0 && markerBytes <= 0xffef) ||
                markerBytes === 0xfffe
              ) {
                // The marker bytes (2) are always followed by
                // the length bytes (2), indicating the length of the
                // marker segment, which includes the length bytes,