blueimp-load-image/js/load-image-exif.js

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

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

/* eslint-disable no-console */

;(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'

  /**
   * Exif tag map
   *
   * @name ExifMap
   * @class
   * @param {number|string} tagCode IFD tag code
   */
  function ExifMap(tagCode) {
    if (tagCode) {
      Object.defineProperty(this, 'map', {
        value: this.ifds[tagCode].map
      })
      Object.defineProperty(this, 'tags', {
        value: (this.tags && this.tags[tagCode]) || {}
      })
    }
  }

  ExifMap.prototype.map = {
    Orientation: 0x0112,
    Thumbnail: 'ifd1',
    Blob: 0x0201, // Alias for JPEGInterchangeFormat
    Exif: 0x8769,
    GPSInfo: 0x8825,
    Interoperability: 0xa005
  }

  ExifMap.prototype.ifds = {
    ifd1: { name: 'Thumbnail', map: ExifMap.prototype.map },
    0x8769: { name: 'Exif', map: {} },
    0x8825: { name: 'GPSInfo', map: {} },
    0xa005: { name: 'Interoperability', map: {} }
  }

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

  /**
   * Returns the Exif Thumbnail data as Blob.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} offset Thumbnail data offset
   * @param {number} length Thumbnail data length
   * @returns {undefined|Blob} Returns the Thumbnail Blob or undefined
   */
  function getExifThumbnail(dataView, offset, length) {
    if (!length) return
    if (offset + length > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid thumbnail data.')
      return
    }
    return new Blob(
      [loadImage.bufferSlice.call(dataView.buffer, offset, offset + length)],
      {
        type: 'image/jpeg'
      }
    )
  }

  var ExifTagTypes = {
    // byte, 8-bit unsigned int:
    1: {
      getValue: function (dataView, dataOffset) {
        return dataView.getUint8(dataOffset)
      },
      size: 1
    },
    // ascii, 8-bit byte:
    2: {
      getValue: function (dataView, dataOffset) {
        return String.fromCharCode(dataView.getUint8(dataOffset))
      },
      size: 1,
      ascii: true
    },
    // short, 16 bit int:
    3: {
      getValue: function (dataView, dataOffset, littleEndian) {
        return dataView.getUint16(dataOffset, littleEndian)
      },
      size: 2
    },
    // long, 32 bit int:
    4: {
      getValue: function (dataView, dataOffset, littleEndian) {
        return dataView.getUint32(dataOffset, littleEndian)
      },
      size: 4
    },
    // rational = two long values, first is numerator, second is denominator:
    5: {
      getValue: function (dataView, dataOffset, littleEndian) {
        return (
          dataView.getUint32(dataOffset, littleEndian) /
          dataView.getUint32(dataOffset + 4, littleEndian)
        )
      },
      size: 8
    },
    // slong, 32 bit signed int:
    9: {
      getValue: function (dataView, dataOffset, littleEndian) {
        return dataView.getInt32(dataOffset, littleEndian)
      },
      size: 4
    },
    // srational, two slongs, first is numerator, second is denominator:
    10: {
      getValue: function (dataView, dataOffset, littleEndian) {
        return (
          dataView.getInt32(dataOffset, littleEndian) /
          dataView.getInt32(dataOffset + 4, littleEndian)
        )
      },
      size: 8
    }
  }
  // undefined, 8-bit byte, value depending on field:
  ExifTagTypes[7] = ExifTagTypes[1]

  /**
   * Returns Exif tag value.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} tiffOffset TIFF offset
   * @param {number} offset Tag offset
   * @param {number} type Tag type
   * @param {number} length Tag length
   * @param {boolean} littleEndian Little endian encoding
   * @returns {object} Tag value
   */
  function getExifValue(
    dataView,
    tiffOffset,
    offset,
    type,
    length,
    littleEndian
  ) {
    var tagType = ExifTagTypes[type]
    var tagSize
    var dataOffset
    var values
    var i
    var str
    var c
    if (!tagType) {
      console.log('Invalid Exif data: Invalid tag type.')
      return
    }
    tagSize = tagType.size * length
    // Determine if the value is contained in the dataOffset bytes,
    // or if the value at the dataOffset is a pointer to the actual data:
    dataOffset =
      tagSize > 4
        ? tiffOffset + dataView.getUint32(offset + 8, littleEndian)
        : offset + 8
    if (dataOffset + tagSize > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid data offset.')
      return
    }
    if (length === 1) {
      return tagType.getValue(dataView, dataOffset, littleEndian)
    }
    values = []
    for (i = 0; i < length; i += 1) {
      values[i] = tagType.getValue(
        dataView,
        dataOffset + i * tagType.size,
        littleEndian
      )
    }
    if (tagType.ascii) {
      str = ''
      // Concatenate the chars:
      for (i = 0; i < values.length; i += 1) {
        c = values[i]
        // Ignore the terminating NULL byte(s):
        if (c === '\u0000') {
          break
        }
        str += c
      }
      return str
    }
    return values
  }

  /**
   * Determines if the given tag should be included.
   *
   * @param {object} includeTags Map of tags to include
   * @param {object} excludeTags Map of tags to exclude
   * @param {number|string} tagCode Tag code to check
   * @returns {boolean} True if the tag should be included
   */
  function shouldIncludeTag(includeTags, excludeTags, tagCode) {
    return (
      (!includeTags || includeTags[tagCode]) &&
      (!excludeTags || excludeTags[tagCode] !== true)
    )
  }

  /**
   * Parses Exif tags.
   *
   * @param {DataView} dataView Data view interface
   * @param {number} tiffOffset TIFF offset
   * @param {number} dirOffset Directory offset
   * @param {boolean} littleEndian Little endian encoding
   * @param {ExifMap} tags Map to store parsed exif tags
   * @param {ExifMap} tagOffsets Map to store parsed exif tag offsets
   * @param {object} includeTags Map of tags to include
   * @param {object} excludeTags Map of tags to exclude
   * @returns {number} Next directory offset
   */
  function parseExifTags(
    dataView,
    tiffOffset,
    dirOffset,
    littleEndian,
    tags,
    tagOffsets,
    includeTags,
    excludeTags
  ) {
    var tagsNumber, dirEndOffset, i, tagOffset, tagNumber, tagValue
    if (dirOffset + 6 > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid directory offset.')
      return
    }
    tagsNumber = dataView.getUint16(dirOffset, littleEndian)
    dirEndOffset = dirOffset + 2 + 12 * tagsNumber
    if (dirEndOffset + 4 > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid directory size.')
      return
    }
    for (i = 0; i < tagsNumber; i += 1) {
      tagOffset = dirOffset + 2 + 12 * i
      tagNumber = dataView.getUint16(tagOffset, littleEndian)
      if (!shouldIncludeTag(includeTags, excludeTags, tagNumber)) continue
      tagValue = getExifValue(
        dataView,
        tiffOffset,
        tagOffset,
        dataView.getUint16(tagOffset + 2, littleEndian), // tag type
        dataView.getUint32(tagOffset + 4, littleEndian), // tag length
        littleEndian
      )
      tags[tagNumber] = tagValue
      if (tagOffsets) {
        tagOffsets[tagNumber] = tagOffset
      }
    }
    // Return the offset to the next directory:
    return dataView.getUint32(dirEndOffset, littleEndian)
  }

  /**
   * Parses tags in a given IFD (Image File Directory).
   *
   * @param {object} data Data object to store exif tags and offsets
   * @param {number|string} tagCode IFD tag code
   * @param {DataView} dataView Data view interface
   * @param {number} tiffOffset TIFF offset
   * @param {boolean} littleEndian Little endian encoding
   * @param {object} includeTags Map of tags to include
   * @param {object} excludeTags Map of tags to exclude
   */
  function parseExifIFD(
    data,
    tagCode,
    dataView,
    tiffOffset,
    littleEndian,
    includeTags,
    excludeTags
  ) {
    var dirOffset = data.exif[tagCode]
    if (dirOffset) {
      data.exif[tagCode] = new ExifMap(tagCode)
      if (data.exifOffsets) {
        data.exifOffsets[tagCode] = new ExifMap(tagCode)
      }
      parseExifTags(
        dataView,
        tiffOffset,
        tiffOffset + dirOffset,
        littleEndian,
        data.exif[tagCode],
        data.exifOffsets && data.exifOffsets[tagCode],
        includeTags && includeTags[tagCode],
        excludeTags && excludeTags[tagCode]
      )
    }
  }

  loadImage.parseExifData = function (dataView, offset, length, data, options) {
    if (options.disableExif) {
      return
    }
    var includeTags = options.includeExifTags
    var excludeTags = options.excludeExifTags || {
      0x8769: {
        // ExifIFDPointer
        0x927c: true // MakerNote
      }
    }
    var tiffOffset = offset + 10
    var littleEndian
    var dirOffset
    var thumbnailIFD
    // Check for the ASCII code for "Exif" (0x45786966):
    if (dataView.getUint32(offset + 4) !== 0x45786966) {
      // No Exif data, might be XMP data instead
      return
    }
    if (tiffOffset + 8 > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid segment size.')
      return
    }
    // Check for the two null bytes:
    if (dataView.getUint16(offset + 8) !== 0x0000) {
      console.log('Invalid Exif data: Missing byte alignment offset.')
      return
    }
    // Check the byte alignment:
    switch (dataView.getUint16(tiffOffset)) {
      case 0x4949:
        littleEndian = true
        break
      case 0x4d4d:
        littleEndian = false
        break
      default:
        console.log('Invalid Exif data: Invalid byte alignment marker.')
        return
    }
    // Check for the TIFF tag marker (0x002A):
    if (dataView.getUint16(tiffOffset + 2, littleEndian) !== 0x002a) {
      console.log('Invalid Exif data: Missing TIFF marker.')
      return
    }
    // Retrieve the directory offset bytes, usually 0x00000008 or 8 decimal:
    dirOffset = dataView.getUint32(tiffOffset + 4, littleEndian)
    // Create the exif object to store the tags:
    data.exif = new ExifMap()
    if (!options.disableExifOffsets) {
      data.exifOffsets = new ExifMap()
      data.exifTiffOffset = tiffOffset
      data.exifLittleEndian = littleEndian
    }
    // Parse the tags of the main image directory (IFD0) and retrieve the
    // offset to the next directory (IFD1), usually the thumbnail directory:
    dirOffset = parseExifTags(
      dataView,
      tiffOffset,
      tiffOffset + dirOffset,
      littleEndian,
      data.exif,
      data.exifOffsets,
      includeTags,
      excludeTags
    )
    if (dirOffset && shouldIncludeTag(includeTags, excludeTags, 'ifd1')) {
      data.exif.ifd1 = dirOffset
      if (data.exifOffsets) {
        data.exifOffsets.ifd1 = tiffOffset + dirOffset
      }
    }
    Object.keys(data.exif.ifds).forEach(function (tagCode) {
      parseExifIFD(
        data,
        tagCode,
        dataView,
        tiffOffset,
        littleEndian,
        includeTags,
        excludeTags
      )
    })
    thumbnailIFD = data.exif.ifd1
    // Check for JPEG Thumbnail offset and data length:
    if (thumbnailIFD && thumbnailIFD[0x0201]) {
      thumbnailIFD[0x0201] = getExifThumbnail(
        dataView,
        tiffOffset + thumbnailIFD[0x0201],
        thumbnailIFD[0x0202] // Thumbnail data length
      )
    }
  }

  // Registers the Exif parser for the APP1 JPEG metadata segment:
  loadImage.metaDataParsers.jpeg[0xffe1].push(loadImage.parseExifData)

  loadImage.exifWriters = {
    // Orientation writer:
    0x0112: function (buffer, data, value) {
      var orientationOffset = data.exifOffsets[0x0112]
      if (!orientationOffset) return buffer
      var view = new DataView(buffer, orientationOffset + 8, 2)
      view.setUint16(0, value, data.exifLittleEndian)
      return buffer
    }
  }

  loadImage.writeExifData = function (buffer, data, id, value) {
    loadImage.exifWriters[data.exif.map[id]](buffer, data, value)
  }

  loadImage.ExifMap = ExifMap

  // Adds the following properties to the parseMetaData callback data:
  // - exif: The parsed Exif tags
  // - exifOffsets: The parsed Exif tag offsets
  // - exifTiffOffset: TIFF header offset (used for offset pointers)
  // - exifLittleEndian: little endian order if true, big endian if false

  // Adds the following options to the parseMetaData method:
  // - disableExif: Disables Exif parsing when true.
  // - disableExifOffsets: Disables storing Exif tag offsets when true.
  // - includeExifTags: A map of Exif tags to include for parsing.
  // - excludeExifTags: A map of Exif tags to exclude from parsing.
})