snipe-it/bower_components/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:
 * http://www.opensource.org/licenses/MIT
 */

/* global define */

;(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'

  loadImage.ExifMap = function () {
    return this
  }

  loadImage.ExifMap.prototype.map = {
    'Orientation': 0x0112
  }

  loadImage.ExifMap.prototype.get = function (id) {
    return this[id] || this[this.map[id]]
  }

  loadImage.getExifThumbnail = function (dataView, offset, length) {
    var hexData,
      i,
      b
    if (!length || offset + length > dataView.byteLength) {
      console.log('Invalid Exif data: Invalid thumbnail data.')
      return
    }
    hexData = []
    for (i = 0; i < length; i += 1) {
      b = dataView.getUint8(offset + i)
      hexData.push((b < 16 ? '0' : '') + b.toString(16))
    }
    return 'data:image/jpeg,%' + hexData.join('%')
  }

  loadImage.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:
  loadImage.exifTagTypes[7] = loadImage.exifTagTypes[1]

  loadImage.getExifValue = function (dataView, tiffOffset, offset, type, length, littleEndian) {
    var tagType = loadImage.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
  }

  loadImage.parseExifTag = function (dataView, tiffOffset, offset, littleEndian, data) {
    var tag = dataView.getUint16(offset, littleEndian)
    data.exif[tag] = loadImage.getExifValue(
      dataView,
      tiffOffset,
      offset,
      dataView.getUint16(offset + 2, littleEndian), // tag type
      dataView.getUint32(offset + 4, littleEndian), // tag length
      littleEndian
    )
  }

  loadImage.parseExifTags = function (dataView, tiffOffset, dirOffset, littleEndian, data) {
    var tagsNumber,
      dirEndOffset,
      i
    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) {
      this.parseExifTag(
        dataView,
        tiffOffset,
        dirOffset + 2 + 12 * i, // tag offset
        littleEndian,
        data
      )
    }
    // Return the offset to the next directory:
    return dataView.getUint32(dirEndOffset, littleEndian)
  }

  loadImage.parseExifData = function (dataView, offset, length, data, options) {
    if (options.disableExif) {
      return
    }
    var tiffOffset = offset + 10
    var littleEndian
    var dirOffset
    var thumbnailData
    // 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 loadImage.ExifMap()
    // Parse the tags of the main image directory and retrieve the
    // offset to the next directory, usually the thumbnail directory:
    dirOffset = loadImage.parseExifTags(
      dataView,
      tiffOffset,
      tiffOffset + dirOffset,
      littleEndian,
      data
    )
    if (dirOffset && !options.disableExifThumbnail) {
      thumbnailData = {exif: {}}
      dirOffset = loadImage.parseExifTags(
        dataView,
        tiffOffset,
        tiffOffset + dirOffset,
        littleEndian,
        thumbnailData
      )
      // Check for JPEG Thumbnail offset:
      if (thumbnailData.exif[0x0201]) {
        data.exif.Thumbnail = loadImage.getExifThumbnail(
          dataView,
          tiffOffset + thumbnailData.exif[0x0201],
          thumbnailData.exif[0x0202] // Thumbnail data length
        )
      }
    }
    // Check for Exif Sub IFD Pointer:
    if (data.exif[0x8769] && !options.disableExifSub) {
      loadImage.parseExifTags(
        dataView,
        tiffOffset,
        tiffOffset + data.exif[0x8769], // directory offset
        littleEndian,
        data
      )
    }
    // Check for GPS Info IFD Pointer:
    if (data.exif[0x8825] && !options.disableExifGps) {
      loadImage.parseExifTags(
        dataView,
        tiffOffset,
        tiffOffset + data.exif[0x8825], // directory offset
        littleEndian,
        data
      )
    }
  }

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

  // Adds the following properties to the parseMetaData callback data:
  // * exif: The exif tags, parsed by the parseExifData method

  // Adds the following options to the parseMetaData method:
  // * disableExif: Disables Exif parsing.
  // * disableExifThumbnail: Disables parsing of the Exif Thumbnail.
  // * disableExifSub: Disables parsing of the Exif Sub IFD.
  // * disableExifGps: Disables parsing of the Exif GPS Info IFD.
}))