blueimp-load-image/js/load-image-iptc.js

/*
 * JavaScript Load Image IPTC Parser
 * https://github.com/blueimp/JavaScript-Load-Image
 *
 * Copyright 2013, Sebastian Tschan
 * Copyright 2018, Dave Bevan
 * https://blueimp.net
 *
 * Licensed under the MIT license:
 * https://opensource.org/licenses/MIT
 */

/* global define, module, require, DataView */

;(function (factory) {
  'use strict'
  if (typeof define === 'function' && define.amd) {
    // Register as an anonymous AMD module:
    define(['./load-image', './load-image-meta'], factory)
  } else if (typeof module === 'object' && module.exports) {
    factory(require('./load-image'), require('./load-image-meta'))
  } else {
    // Browser globals:
    factory(window.loadImage)
  }
})(function (loadImage) {
  'use strict'

  /**
   * IPTC tag map
   *
   * @name IptcMap
   * @class
   */
  function IptcMap() {}

  IptcMap.prototype.map = {
    ObjectName: 5
  }

  IptcMap.prototype.types = {
    0: 'Uint16', // ApplicationRecordVersion
    200: 'Uint16', // ObjectPreviewFileFormat
    201: 'Uint16', // ObjectPreviewFileVersion
    202: 'binary' // ObjectPreviewData
  }

  /**
   * Retrieves IPTC tag value
   *
   * @param {number|string} id IPTC tag code or name
   * @returns {object} IPTC tag value
   */
  IptcMap.prototype.get = function (id) {
    return this[id] || this[this.map[id]]
  }

  /**
   * Retrieves string for the given DataView and range
   *
   * @param {DataView} dataView Data view interface
   * @param {number} offset Offset start
   * @param {number} length Offset length
   * @returns {string} String value
   */
  function getStringValue(dataView, offset, length) {
    var outstr = ''
    var end = offset + length
    for (var n = offset; n < end; n += 1) {
      outstr += String.fromCharCode(dataView.getUint8(n))
    }
    return outstr
  }

  /**
   * Retrieves tag value for the given DataView and range
   *
   * @param {number} tagCode tag code
   * @param {IptcMap} map IPTC tag map
   * @param {DataView} dataView Data view interface
   * @param {number} offset Range start
   * @param {number} length Range length
   * @returns {object} Tag value
   */
  function getTagValue(tagCode, map, dataView, offset, length) {
    if (map.types[tagCode] === 'binary') {
      return new Blob([dataView.buffer.slice(offset, offset + length)])
    }
    if (map.types[tagCode] === 'Uint16') {
      return dataView.getUint16(offset)
    }
    return getStringValue(dataView, offset, length)
  }

  /**
   * Combines IPTC value with existing ones.
   *
   * @param {object} value Existing IPTC field value
   * @param {object} newValue New IPTC field value
   * @returns {object} Resulting IPTC field value
   */
  function combineTagValues(value, newValue) {
    if (value === undefined) return newValue
    if (value instanceof Array) {
      value.push(newValue)
      return value
    }
    return [value, newValue]
  }

  /**
   * Parses IPTC tags.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} segmentOffset Segment offset
   * @param {number} segmentLength Segment length
   * @param {object} data Data export object
   * @param {object} includeTags Map of tags to include
   * @param {object} excludeTags Map of tags to exclude
   */
  function parseIptcTags(
    dataView,
    segmentOffset,
    segmentLength,
    data,
    includeTags,
    excludeTags
  ) {
    var value, tagSize, tagCode
    var segmentEnd = segmentOffset + segmentLength
    var offset = segmentOffset
    while (offset < segmentEnd) {
      if (
        dataView.getUint8(offset) === 0x1c && // tag marker
        dataView.getUint8(offset + 1) === 0x02 // record number, only handles v2
      ) {
        tagCode = dataView.getUint8(offset + 2)
        if (
          (!includeTags || includeTags[tagCode]) &&
          (!excludeTags || !excludeTags[tagCode])
        ) {
          tagSize = dataView.getInt16(offset + 3)
          value = getTagValue(tagCode, data.iptc, dataView, offset + 5, tagSize)
          data.iptc[tagCode] = combineTagValues(data.iptc[tagCode], value)
          if (data.iptcOffsets) {
            data.iptcOffsets[tagCode] = offset
          }
        }
      }
      offset += 1
    }
  }

  /**
   * Tests if field segment starts at offset.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} offset Segment offset
   * @returns {boolean} True if '8BIM<EOT><EOT>' exists at offset
   */
  function isSegmentStart(dataView, offset) {
    return (
      dataView.getUint32(offset) === 0x3842494d && // Photoshop segment start
      dataView.getUint16(offset + 4) === 0x0404 // IPTC segment start
    )
  }

  /**
   * Returns header length.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} offset Segment offset
   * @returns {number} Header length
   */
  function getHeaderLength(dataView, offset) {
    var length = dataView.getUint8(offset + 7)
    if (length % 2 !== 0) length += 1
    // Check for pre photoshop 6 format
    if (length === 0) {
      // Always 4
      length = 4
    }
    return length
  }

  loadImage.parseIptcData = function (dataView, offset, length, data, options) {
    if (options.disableIptc) {
      return
    }
    var markerLength = offset + length
    while (offset + 8 < markerLength) {
      if (isSegmentStart(dataView, offset)) {
        var headerLength = getHeaderLength(dataView, offset)
        var segmentOffset = offset + 8 + headerLength
        if (segmentOffset > markerLength) {
          // eslint-disable-next-line no-console
          console.log('Invalid IPTC data: Invalid segment offset.')
          break
        }
        var segmentLength = dataView.getUint16(offset + 6 + headerLength)
        if (offset + segmentLength > markerLength) {
          // eslint-disable-next-line no-console
          console.log('Invalid IPTC data: Invalid segment size.')
          break
        }
        // Create the iptc object to store the tags:
        data.iptc = new IptcMap()
        if (!options.disableIptcOffsets) {
          data.iptcOffsets = new IptcMap()
        }
        parseIptcTags(
          dataView,
          segmentOffset,
          segmentLength,
          data,
          options.includeIptcTags,
          options.excludeIptcTags || { 202: true } // ObjectPreviewData
        )
        return
      }
      // eslint-disable-next-line no-param-reassign
      offset += 1
    }
  }

  // Registers this IPTC parser for the APP13 JPEG metadata segment:
  loadImage.metaDataParsers.jpeg[0xffed].push(loadImage.parseIptcData)

  loadImage.IptcMap = IptcMap

  // Adds the following properties to the parseMetaData callback data:
  // - iptc: The iptc tags, parsed by the parseIptcData method

  // Adds the following options to the parseMetaData method:
  // - disableIptc: Disables IPTC parsing when true.
  // - disableIptcOffsets: Disables storing IPTC tag offsets when true.
  // - includeIptcTags: A map of IPTC tags to include for parsing.
  // - excludeIptcTags: A map of IPTC tags to exclude from parsing.
})