load-image-meta.js
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/*
* JavaScript Load Image Meta
* https://github.com/blueimp/JavaScript-Load-Image
*
* Copyright 2013, Sebastian Tschan
* https://blueimp.net
*
* Image meta data handling implementation
* based on the help and contribution of
* Achim Stöhr.
*
* Licensed under the MIT license:
* http://www.opensource.org/licenses/MIT
*/
/*global define, module, require, window, DataView, Blob, Uint8Array, console */
;(function (factory) {
'use strict'
if (typeof define === 'function' && define.amd) {
// Register as an anonymous AMD module:
define(['load-image'], factory)
} else if (typeof module === 'object' && module.exports) {
factory(require('./load-image'))
} else {
// Browser globals:
factory(window.loadImage)
}
}(function (loadImage) {
'use strict'
var hasblobSlice = window.Blob && (Blob.prototype.slice ||
Blob.prototype.webkitSlice || Blob.prototype.mozSlice)
loadImage.blobSlice = hasblobSlice && function () {
var slice = this.slice || this.webkitSlice || this.mozSlice
return slice.apply(this, arguments)
}
loadImage.metaDataParsers = {
jpeg: {
0xffe1: [] // APP1 marker
}
}
// Parses image meta data and calls the callback with an object argument
// with the following properties:
// * imageHead: The complete image head as ArrayBuffer (Uint8Array for IE10)
// The options arguments accepts an object and supports the following properties:
// * maxMetaDataSize: Defines the maximum number of bytes to parse.
// * disableImageHead: Disables creating the imageHead property.
loadImage.parseMetaData = function (file, callback, options) {
options = options || {}
var that = this
// 256 KiB should contain all EXIF/ICC/IPTC segments:
var maxMetaDataSize = options.maxMetaDataSize || 262144
var data = {}
var noMetaData = !(window.DataView && file && file.size >= 12 &&
file.type === 'image/jpeg' && loadImage.blobSlice)
if (noMetaData || !loadImage.readFile(
loadImage.blobSlice.call(file, 0, maxMetaDataSize),
function (e) {
if (e.target.error) {
// FileReader error
console.log(e.target.error)
callback(data)
return
}
// 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 buffer = e.target.result
var dataView = new DataView(buffer)
var offset = 2
var maxOffset = dataView.byteLength - 4
var headLength = offset
var markerBytes
var markerLength
var parsers
var i
// Check for the JPEG marker (0xffd8):
if (dataView.getUint16(0) === 0xffd8) {
while (offset < maxOffset) {
markerBytes = dataView.getUint16(offset)
// Search for APPn (0xffeN) and COM (0xfffe) markers,
// which contain application-specific meta-data 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,
// but not the marker bytes, so we add 2:
markerLength = dataView.getUint16(offset + 2) + 2
if (offset + markerLength > dataView.byteLength) {
console.log('Invalid meta data: Invalid segment size.')
break
}
parsers = loadImage.metaDataParsers.jpeg[markerBytes]
if (parsers) {
for (i = 0; i < parsers.length; i += 1) {
parsers[i].call(
that,
dataView,
offset,
markerLength,
data,
options
)
}
}
offset += markerLength
headLength = offset
} else {
// Not an APPn or COM marker, probably safe to
// assume that this is the end of the meta data
break
}
}
// Meta length must be longer than JPEG marker (2)
// plus APPn marker (2), followed by length bytes (2):
if (!options.disableImageHead && headLength > 6) {
if (buffer.slice) {
data.imageHead = buffer.slice(0, headLength)
} else {
// Workaround for IE10, which does not yet
// support ArrayBuffer.slice:
data.imageHead = new Uint8Array(buffer)
.subarray(0, headLength)
}
}
} else {
console.log('Invalid JPEG file: Missing JPEG marker.')
}
callback(data)
},
'readAsArrayBuffer'
)) {
callback(data)
}
}
}))