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.

$3

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

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

$3

It is possible to specify a custom executable.

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

$3

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

`bash
npm i --save dist-exiftool
`

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

$3

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.

`javascript
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.

`javascript
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.

$3

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

`javascript
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)
`

`javascript
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
`

$3

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.

`javascript
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)
`

`fs
{ 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 ',
ImageSize: '362x250',
Megapixels: 0.09 } ],
error: null }
`

$3

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.,

`javascript
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'].

`javascript
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)
`

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

$3

`javascript
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)
`

`javascript
{
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'
}
`

$3

`javascript
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)
`

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

$3

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.

`javascript
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)
`

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

`javascript
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)

`

`javascript
{
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
}
`




$3

`javascript
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)
`

`javascript
{ 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:

`html











Hello world




`

$3

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

`javascript
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
...
`

$3

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.

`js
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)
`

$3

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:

`js
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)
`

$3

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.

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

`powershell
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.

$3

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.

`js
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

`js
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

$3

For example, when trying to write metadata:

`js
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}...some data...{ready}. 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:

`js
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