labsrs-ref/node-exiftool

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

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.

Important: since version 2, 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.

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

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

Custom Executable

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

dist-exiftool

npm i --save dist-exiftool

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

Writing Metadata

Since version 2.1.0, you can write metadata. The API is: writeMetadata(file, data, args), where file is a string with path to your file, data is an object, 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 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)

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

Reading Single File

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

const ep = new exiftool.ExiftoolProcess()
ep
  .open()
  .then((pid) => console.log('Started exiftool process %s', pid))
  .then(() => ep.readMetadata('photo.jpg'))
  .then(console.log)
  // repeat as many times as required
  .then(() => ep.close())
  .then(() => console.log('Closed exiftool'))

{
  data: [
    {
      SourceFile: 'photo.jpg',
      ExifToolVersion: 10.16,
      FileName: 'photo.jpg',
      Directory: '.',
      FileSize: '51 kB',
      FileModifyDate: '2016:05:15 22:59:45+01:00',
      FileAccessDate: '2016:05:15 23:05:27+01:00',
      FileInodeChangeDate: '2016:05:15 22:59:45+01:00',
      FilePermissions: 'rw-r--r--',
      FileType: 'JPEG',
      FileTypeExtension: 'jpg',
      MIMEType: 'image/jpeg',
      XMPToolkit: 'Image::ExifTool 10.11',
      CreatorWorkURL: 'https://sobesednik.media',
      Scene: '011200',
      Creator: 'Anton',
      ImageWidth: 500,
      ImageHeight: 333,
      EncodingProcess: 'Baseline DCT, Huffman coding',
      BitsPerSample: 8,
      ColorComponents: 3,
      YCbCrSubSampling: 'YCbCr4:2:0 (2 2)',
      ImageSize: '500x333',
      Megapixels: 0.167
    }
  ],
  error: null
}

Reading Directory

const ep = new exiftool.ExiftoolProcess()
ep
  .readMetadata('DIR')
  .then(console.log)

{
  data: [
    {
      SourceFile: 'DIR/IMG_9857.JPG',
      ExifToolVersion: 10.16,
      FileName: 'IMG_9857.JPG',
      Directory: 'DIR',
      FileSize: '51 kB',
      FileModifyDate: '2016:05:15 23:06:58+01:00',
      FileAccessDate: '2016:05:15 23:06:58+01:00',
      FileInodeChangeDate: '2016:05:15 23:06:58+01:00',
      FilePermissions: 'rw-r--r--',
      FileType: 'JPEG',
      FileTypeExtension: 'jpg',
      MIMEType: 'image/jpeg',
      XMPToolkit: 'Image::ExifTool 10.11',
      CreatorWorkURL: 'https://sobesednik.media',
      Scene: '011200',
      Creator: 'Anton',
      ImageWidth: 500,
      ImageHeight: 333,
      EncodingProcess: 'Baseline DCT, Huffman coding',
      BitsPerSample: 8,
      ColorComponents: 3,
      YCbCrSubSampling: 'YCbCr4:2:0 (2 2)',
      ImageSize: '500x333',
      Megapixels: 0.167
    },
    {
      SourceFile: 'DIR/IMG_9858.JPG',
      ExifToolVersion: 10.16,
      FileName: 'IMG_9858.JPG',
      Directory: 'DIR',
      FileSize: '52 kB',
      FileModifyDate: '2016:05:15 23:06:58+01:00',
      FileAccessDate: '2016:05:15 23:06:58+01:00',
      FileInodeChangeDate: '2016:05:15 23:06:58+01:00',
      FilePermissions: 'rw-r--r--',
      FileType: 'JPEG',
      FileTypeExtension: 'jpg',
      MIMEType: 'image/jpeg',
      ExifByteOrder: 'Big-endian (Motorola, MM)',
      Orientation: 'Rotate 90 CW',
      XResolution:72,
      YResolution:72,
      ResolutionUnit: 'inches',
      YCbCrPositioning: 'Centered',
      XMPToolkit: 'Image::ExifTool 10.11',
      CreatorWorkURL: 'https://sobesednik.media',
      Scene: '011200',
      Creator: 'Anton',
      ImageWidth: 500,
      ImageHeight: 334,
      EncodingProcess: 'Baseline DCT, Huffman coding',
      BitsPerSample: 8,
      ColorComponents: 3,
      YCbCrSubSampling: 'YCbCr4:2:0 (2 2)',
      ImageSize: '500x334',
      Megapixels: 0.167
    }
  ],
  error: '1 directories scanned\n    2 image files read'
}

Reading Non-existent File

const ep = new exiftool.ExiftoolProcess()
ep
  .readMetadata('filenotfound.jpg')
  .then(console.log)

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

Incorrect file format

const ep = new exiftool.ExiftoolProcess()
ep
  .readMetadata('url.html')
  .then(console.log)

{
  data: [
    {
      SourceFile: 'url.html',
      ExifToolVersion: 10.16,
      FileName: 'url.html',
      Directory: '.',
      FileSize: '574 bytes',
      FileModifyDate: '2016:05:15 23:28:30+01:00',
      FileAccessDate: '2016:05:15 23:28:30+01:00',
      FileInodeChangeDate: '2016:05:15 23:28:30+01:00',
      FilePermissions: 'rw-r-----',
      Error: 'File format error'
    }
  ],
  error: null
}

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 ep = new exiftool.ExiftoolProcess()
// include only some tags
ep
  .readMetadata('photo.jpg', ['Creator', 'CreatorWorkURL', 'Orientation'])
  .then(console.log)

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

const ep = new exiftool.ExiftoolProcess()
// exclude some tags and groups of tags
ep
  .readMetadata('photo.jpg', ['-ExifToolVersion', '-File:all'])
  .then(console.log)

{
  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: 'Anton',
      ImageSize: '500x334',
      Megapixels: 0.167
    }
  ],
  error: null
}

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 ep = new exiftool.ExiftoolProcess()
const cp = require('child_process')

ep
  .on(exiftool.events.OPEN, (pid) => {
    console.log('Started exiftool process %s', pid)
  })
ep
  .on(exiftool.events.EXIT, () => {
    console.log('exiftool process exited')
    ep.open()
  })

ep
  .open()
  .then(() => cp.execSync('pkill -f exiftool'))

Started exiftool process 95230
exiftool process exited
Started exiftool process 95232

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%

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