node-exiftool

A Node.js interface to the exiftool command-line application.

Exiftool is an amazing tool written by Phil Harvey in Perl which can read and write metadata to a number of file formats. It is very powerful and allows to do such things as extracting orientation from JPEG files uploaded to your server by users to rotate generated previews accordingly, as well as appending copyright information to photos using IPTC standard.

exiftool is not distributed with node-exiftool. The module will try to spawn exiftool, therefore you must install it manually. You can also use dist-exiftool package which will install exiftool distribution appropriate for your platform. See below for details about how to use node-exiftool with dist-exiftool.

Usage

The module spawns an exiftool process with -stay_open True -@ - arguments, so that there is no overhead related to starting a new process to read every file or directory. The package creates a process asynchronously and listens for stdout and stderr data events and uses promises thus avoiding blocking the Node's event loop.

Require

By default, the executable is hard-coded to be just exiftool. You must have it you path for this method to work.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()

Custom Executable

It is possible to specify a custom executable.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess('/usr/local/exiftool')

dist-exiftool

Or you can install dist-exiftool, which allows to install exiftool from npm.

npm i --save dist-exiftool

const exiftool = require('node-exiftool')
const exiftoolBin = require('dist-exiftool')
const ep = new exiftool.ExiftoolProcess(exiftoolBin)

Opening and Closing

After creating an instance of ExiftoolProcess, it must be opened. When finished working with it, it should be closed, when -stay_open False will be written to its stdin to exit the process.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // read and write metadata operations
  .then(() => ep.close())
  .then(() => console.log('Closed exiftool'))
  .catch(console.error)

Passing Options

exiftool will be open with child_process.spawn, and you can specify options object which will passed to the spawn method.

const exiftool = require('node-exiftool')
const options = {
  detached: true,
  env: Object.assign({}, process.env, {
    ENVIRONMENT_VARIABLE: 1,
  }),
}
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open(options)
  .then(() => ep.close())
  .catch(console.error)

Since passing options is available, a check will be made to make sure that stderr and stdout streams are readable, and stdin is writable. Therefore, you cannot pass { stdio: 'ignore' } as an option.

Reading Metadata

You are required to open the exiftool process first, after which you will be able to read and write metadata.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // display pid
  .then((pid) => console.log('Started exiftool process %s', pid))
  .then(() => ep.readMetadata('photo.jpg', ['-File:all']))
  .then(console.log, console.error)
  .then(() => ep.readMetadata('photo2.jpg', ['-File:all']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .then(() => console.log('Closed exiftool'))
  .catch(console.error)

Started exiftool process 29671
{ data:
   [ { SourceFile: 'image.jpg',
       ExifToolVersion: 10.4,
       XMPToolkit: 'Image::ExifTool 10.40',
       CreatorWorkURL: 'https://sobesednik.media',
       Scene: '011200',
       Creator: 'Photographer Name',
       Author: 'Author',
       ImageSize: '500x333',
       Megapixels: 0.167 } ],
  error: null }
{ data:
   [ { SourceFile: 'image2.jpg',
       ExifToolVersion: 10.4,
       Orientation: 'Rotate 90 CW',
       XResolution: 72,
       YResolution: 72,
       ResolutionUnit: 'inches',
       YCbCrPositioning: 'Centered',
       XMPToolkit: 'Image::ExifTool 10.40',
       CreatorWorkURL: 'https://sobesednik.media',
       Scene: '011200',
       Creator: 'Photographer Name',
       Author: 'Author',
       ImageSize: '500x334',
       Megapixels: 0.167 } ],
  error: null }
Closed exiftool

Reading Metadata from a Readable Stream

You can read metadata from a stream the same way you read a file metadata. node-exiftool will create a temporary file and pipe your Readable into it, then pass the path to exiftool. After the result is received from exiftool, the temp file will be removed.

const exiftoolBin = require('dist-exiftool')
const exiftool =  require('exiftool')
const fs = require('fs')
const path = require('path')
 
const ep = new exiftool.ExiftoolProcess(exiftoolBin)
 
const PHOTO_PATH = path.join(__dirname, 'photo.jpg')
const rs = fs.createReadStream(PHOTO_PATH)
 
ep.open()
    .then(() => ep.readMetadata(rs, ['-File:all']))
    .then((res) => {
        console.log(res)
    })
    .then(() => ep.close(), () => ep.close())
    .catch(console.error)

{ data:
   [ { SourceFile: '/var/folders/s0/truth-covered-in-security/T/wrote-44788.data',
       ExifToolVersion: 10.53,
       XResolution: 72,
       YResolution: 72,
       ResolutionUnit: 'inches',
       YCbCrPositioning: 'Centered',
       Copyright: 'sobesednik.media 2017',
       XMPToolkit: 'Image::ExifTool 10.40',
       Author: 'Author <author@sobes.io>',
       ImageSize: '362x250',
       Megapixels: 0.09 } ],
  error: null }

Writing Metadata

You can write metadata with node-exiftool. The API is: ep.writeMetadata(file:string, data:object, args:array), where file is a path to the file, data is metadata to add, e.g.,

const data = {
  all: '',
  comment: 'Exiftool rules!', // has to come after `all` in order not to be removed
  'Keywords+': [ 'keywordA', 'keywordB' ],
}

and args is an array of any other arguments you wish to pass, e.g,. ['overwrite_original'].

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  .then(() => ep.writeMetadata('destination.jpg', {
    all: '', // remove existing tags
    comment: 'Exiftool rules!',
    'Keywords+': [ 'keywordA', 'keywordB' ],
  }, ['overwrite_original']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

{ data: null, error: '1 image files updated' }

Reading Directory

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // read directory
  .then(() => ep.readMetadata('DIR', ['-File:all']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

{
  data: [
    { SourceFile: 'DIR/IMG_9859.JPG',
       ExifToolVersion: 10.4,
       Orientation: 'Rotate 90 CW',
       XResolution: 72,
       YResolution: 72,
       ResolutionUnit: 'inches',
       YCbCrPositioning: 'Centered',
       XMPToolkit: 'Image::ExifTool 10.40',
       CreatorWorkURL: 'https://sobesednik.media',
       Scene: '011200',
       Creator: 'Photographer Name',
       Author: 'Author',
       ImageSize: '500x334',
       Megapixels: 0.167 },
     { SourceFile: 'DIR/IMG_9860.JPG',
       ExifToolVersion: 10.4,
       XMPToolkit: 'Image::ExifTool 10.40',
       CreatorWorkURL: 'https://sobesednik.media',
       Scene: '011200',
       Creator: 'Photographer Name',
       Author: 'Author',
       ImageSize: '500x334',
       Megapixels: 0.167 }
  ],
  error: '1 directories scanned\n    2 image files read'
}

Reading Non-existent File

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // try to read file which does not exist
  .then(() => ep.readMetadata('filenotfound.jpg'))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

{
  data: null,
  error: 'File not found: filenotfound.jpg'
}

Custom Arguments

You can pass arguments which you wish to use in the exiftool command call. They will be automatically prepended with the - sign so you don't have to do it manually.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // include only some tags
  .then(() => ep.readMetadata('photo.jpg', ['Creator', 'CreatorWorkURL', 'Orientation']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

{
  data: [
    {
      SourceFile: 'photo.jpg',
      Creator: 'Photographer Name',
      CreatorWorkURL: 'https://sobesednik.media',
      Orientation: 'Rotate 90 CW'
    }
  ],
  error: null
}

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  // exclude some tags and groups of tags
  .then(() => ep.readMetadata('image.jpg', ['-ExifToolVersion', '-File:all']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)
 

{
  data: [
    {
      SourceFile: 'photo.jpg',
      Orientation: 'Rotate 90 CW',
      XResolution: 72,
      YResolution: 72,
      ResolutionUnit: 'inches',
      YCbCrPositioning: 'Centered',
      XMPToolkit: 'Image::ExifTool 10.11',
      CreatorWorkURL: 'https://sobesednik.media',
      Scene: '011200',
      Creator: 'Photographer Name',
      ImageSize: '500x334',
      Megapixels: 0.167
    }
  ],
  error: null
}

Reading HTML

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  .then(() => ep.readMetadata('url.html', ['-File:all']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

{ data:
   [ { SourceFile: 'url.html',
       ExifToolVersion: 10.4,
       Title: 'Some web page',
       Keywords: 'fire, in, your, eyes, etc.',
       Description: 'Programming: Official sponsor of Open Source since ever.' } ],
  error: null }

html:

<!DOCTYPE html>
 
<html>
    <head>
        <title>Some web page</title>
        <meta name="keywords" content="fire, in, your, eyes, etc.">
        <meta name="description" content="Programming: Official sponsor of Open Source since ever.">
    </head>
    <body>
        <p>Hello world</p>
    </body>
</html>

Events

You can also listen for OPEN and EXIT events. For example, if the exiftool process crashed, you might want to restart it.

const exiftool = require('node-exiftool')
const cp = require('child_process')
 
function killProcess(name) {
  return new Promise((resolve, reject) => {
    cp.exec(`pkill -f ${name}`, (err, stdout, stderr) => {
      if(err) return reject(err)
      return resolve({ stdout, stderr })
    })
  })
}
 
function openAndKill(_ep) {
  return _ep
    .open()
    .then(() => killProcess('exiftool'))
    .catch(console.error)
}
 
const ep = new exiftool.ExiftoolProcess()
 
ep.on(exiftool.events.OPEN, (pid) => {
  console.log('Started exiftool process %s', pid)
})
 
ep.on(exiftool.events.EXIT, () => {
  console.log('exiftool process exited')
  return new Promise(r => setTimeout(r, 200))
    .then(() => openAndKill(ep))
})
 
openAndKill(ep)

Started exiftool process 28566
exiftool process exited
Started exiftool process 28569
exiftool process exited
...

Stream Encoding

By default, setEncoding('utf8') will be called on stdout and stderr streams, and stdin will be written with utf8 encoding (this is Node's default on a Mac at least). If you wish to use system's default encoding, pass null when opening the process. If you want to set some other encoding, specify it as a string. Node's supported encodings.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
Promise.resolve()
  .then(() =>
    // streams' encoding is utf8, next stdin write with utf8
    ep.open('utf8').then(() => ep.close())
  )
  .then(() =>
    // encoding will explicitly be not set
    ep.open(null).then(() => ep.close())
  )
  .then(() =>
    // encoding will be set to default utf8
    ep.open().then(() => ep.close())
  )
  .catch(console.error)

Writing Tags for Adobe in UTF8

Some metadata must be written in utf8 encoding, for example to be recognized by Adobe products. However, IPTC fields are encoded in Latin1, so you need to explicitly pass codedcharacterset=utf8 argument. For example, Caption-Abstract is an IPTC tag, so to write it in utf8, do the following:

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
const metadata = {
    all: '', // remove all metadata at first
    Title: 'åäö',
    LocalCaption: 'local caption',
    'Caption-Abstract': 'Câptïön \u00C3bstráct: åäö',
    Copyright: '2017 ©',
    'Keywords+': [ 'këywôrd \u00C3…', 'keywórdB ©˙µå≥' ],
    Creator: 'Mr Author',
    Rating: 5,
}
 
const file = 'file.jpg'
 
ep
  .open()
  // use codedcharacterset
  .then(() => ep.writeMetadata(file, metadata, ['codedcharacterset=utf8']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

Using Detached Mode on Windows

You can spawn exiftool with { detached: true } option if you need to manually handle its exit independent of your application. On Linux, the new process will be made a leader of its process group, and will not quit with the Node app. On Windows, the process will not quit either, however, there will be two exiftool processes: one returned by the child_process.spawn method, and a second one, started by exiftool.exe itself. There is also going to appear conhost.exe, if the parent node application is not attached to a terminal.

wmic process where "caption='node.exe' or caption='exiftool.exe' or caption='conhost.exe'" get caption,processid,parentprocessid

Caption       ParentProcessId  ProcessId
node.exe      3464             5752
exiftool.exe  5752             6096
exiftool.exe  6096             4588
conhost.exe   4588             4016

Because Windows will throw an error when trying to kill a process group by passing -pid to process.kill, you should find the second exiftool process by its parent pid (returned with ep.open()), and kill it manually, e.g., with cp.exec('taskkill /F /T /PID ${pid}'). Check the detached-true test for more insight.

Reading utf8 Encoded Filename on Windows

If you're on Windows and your active page is different from utf8, you should pass charset filename=utf8 when trying to read a file. It shouldn't be a problem on a Mac.

An error you can see is: File not found: Fọto.jpg or whatever filename you have. To fix it, set filename charset to utf8.

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  .then(() => ep.readMetadata('phôtò.jpg', ['charset filename=utf8']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

To print code page number on Windows, do

const child_process = require('child_process')
function printCHCP() {
  return new Promise((resolve, reject) => {
    child_process.exec('chcp', (err, stdout, stderr) => {
      if (err) return reject(err)
      resolve({ stdout, stderr })
    })
  })
}
printCHCP().then(console.log, console.error)

Example output: Active code page: 437. utf8's number is 65001 (on win)

• Special characters don't display properly in my Windows console
• Passing filenames with Unicode characters to ExifTool

How Does It Work

For example, when trying to write metadata:

const exiftool = require('node-exiftool')
const ep = new exiftool.ExiftoolProcess()
 
ep
  .open()
  .then(() => ep.writeMetadata('destination.jpg', {
    all: '', // remove existing tags
    comment: 'Exiftool example',
    'Keywords+': [ 'keywordA', 'keywordB' ],
  }, ['overwrite_original']))
  .then(console.log, console.error)
  .then(() => ep.close())
  .catch(console.error)

Internally, the following command will be sent to exiftool's stdin when it's open:

-all=
-comment=Exiftool example
-Keywords+=keywordA
-Keywords+=keywordB
-overwrite_original
-json
-s
destination.jpg
-echo1
{begin529963}
-echo2
{begin529963}
-echo4
{ready529963}
-execute529963

And the write promise will be resolved when the process writes

{begin669103}
{ready669103}

to stdout, and

{begin513858}
    1 image files updated
{ready513858}

to stderr. There's a regex transform stream which is available for reading when it sees a block like {begin<N>}...some data...{ready<N>}. Once both stderr and stdout data have been received, the promise returned by writeMetadata function will be resolved.

Benchmark

To start the benchmark, execute npm run bench. It will scan all files in the benchmark/photos directory, and if none was found, will work on test fixtures. Here are some of our results:

> node benchmark/run

/node-exiftool/benchmark/photos/IMG_3051.JPG: 168ms
/node-exiftool/benchmark/photos/IMG_3052.JPG: 166ms
/node-exiftool/benchmark/photos/IMG_3053.JPG: 168ms
/node-exiftool/benchmark/photos/IMG_3054.JPG: 166ms
/node-exiftool/benchmark/photos/IMG_3055.JPG: 165ms
/node-exiftool/benchmark/photos/IMG_3056.JPG: 158ms
/node-exiftool/benchmark/photos/IMG_3057.JPG: 158ms
/node-exiftool/benchmark/photos/IMG_3058.JPG: 162ms
/node-exiftool/benchmark/photos/IMG_3059.JPG: 158ms
/node-exiftool/benchmark/photos/IMG_3060.JPG: 158ms
/node-exiftool/benchmark/photos/IMG_3061.JPG: 157ms
/node-exiftool/benchmark/photos/IMG_3051.JPG: 65ms
/node-exiftool/benchmark/photos/IMG_3052.JPG: 20ms
/node-exiftool/benchmark/photos/IMG_3053.JPG: 22ms
/node-exiftool/benchmark/photos/IMG_3054.JPG: 23ms
/node-exiftool/benchmark/photos/IMG_3055.JPG: 22ms
/node-exiftool/benchmark/photos/IMG_3056.JPG: 22ms
/node-exiftool/benchmark/photos/IMG_3057.JPG: 22ms
/node-exiftool/benchmark/photos/IMG_3058.JPG: 22ms
/node-exiftool/benchmark/photos/IMG_3059.JPG: 20ms
/node-exiftool/benchmark/photos/IMG_3060.JPG: 21ms
/node-exiftool/benchmark/photos/IMG_3061.JPG: 20ms

Exiftool
Read 11 files
Total time: 1784ms
Average time: 162.18ms

Exiftool Open
Read 11 files
Total time: 378ms
Average time: 34.36ms

Exiftool Open was faster by 471%

Testing

We're using exiftool-context to test with zoroaster.

Make sure to do the following in tests, when testing current version:

const context = require('exiftool-context')
const exiftool = require('../../src/')
 
context.globalExiftoolConstructor = exiftool.ExiftoolProcess

Otherwise, the context will use a stable version which it installs independently.

Metadata

Metadata is awesome and although it can increase the file size, it preserves copyright and allows to find out additional information and the author of an image/movie. Let's all use metadata.

Resources

Exiftool Documentation