Fast, cross-platform Node.js access to ExifTool.
If links are broken, please read this on exiftool-vendored.js.org.
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Best-of-class cross-platform performance and reliability.
Expect an order of magnitude faster performance than other packages.
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Proper extraction of
- dates with correct timezone offset encoding, when available)
- latitudes & longitudes as floats (where negative values indicate west or south of the meridian)
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Support for
- reading tags
- extracting embedded binaries, like thumbnail and preview images
- writing tags
- rescuing metadata
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Robust type definitions of the top 99.5% tags used by over 6,000 different camera makes and models (see an example)
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Auditable ExifTool source code (the vendored code is checksum verified)
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Automated updates to ExifTool (as new versions come out monthly)
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Robust test coverage, performed with the latest Node v6, v8, and v10 on Linux, Mac, & Windows.
yarn add exiftool-vendored
or
npm install --save exiftool-vendored
Note that exiftool-vendored provides an installation of ExifTool relevant
for your local platform through
optionalDependencies.
You shouldn't include either the exiftool-vendored.exe or
exiftool-vendored.pl as direct dependencies to your project.
See the CHANGELOG for breaking changes since you last updated.
There are many configuration options to ExifTool, but all values have (more or less sensible) defaults.
Those defaults have been used to create the exiftool
singleton. Feel free to review the ExifTool constructor
parameters and override default values where
appropriate if the defaults wont' work for you, but you should use your
singleton to minimize system load. Note that if you don't use the default
singleton, you don't need to .end() it.
// We're using the singleton here for convenience:
const exiftool = require("exiftool-vendored").exiftool
// And to verify everything is working:
exiftool
.version()
.then(version => console.log(`We're running ExifTool v${version}`))ExifTool.read() returns a Promise to a Tags instance. Note
that errors may be returned either by rejecting the promise, or for less
severe problems, via the errors field.
All other public ExifTool methods return Promise<void>, and will reject
the promise if the operation is not successful.
ExifTool has a pretty exhaustive set of error checking, and many "errors" are actually non-fatal warnings about invalid tag structures that seem to be regularly found in otherwise-not-corrupt images.
If we rejected every read or write when any error happened, this would
prevent reading and/or writing to otherwise-ok files. To "demote" errors to be
warnings that don't reject the underlying task, you can provide either a
minorErrorsRegExp, or an
implementation of
rejectTaskOnStderr.
Either of these parameters are provided to the ExifTool constructor.
To enable trace, debug, info, warning, or error logging from this library and
the underlying batch-cluster library,
usesetLogger. Example
code can be found
here.
ExifTool instances emits events for "startError", "taskError", "endError", "beforeEnd", and "end" that you can register listeners for, using on.
exiftool
.read("path/to/image.jpg")
.then((tags /*: Tags */) =>
console.log(
`Make: ${tags.Make}, Model: ${tags.Model}, Errors: ${tags.errors}`
)
)
.catch(err => console.error("Something terrible happened: ", err))Extract the low-resolution thumbnail in path/to/image.jpg, write it to
path/to/thumbnail.jpg, and return a Promise<void> that is fulfilled
when the image is extracted:
exiftool.extractThumbnail("path/to/image.jpg", "path/to/thumbnail.jpg")Extract the Preview image (only found in some images):
exiftool.extractPreview("path/to/image.jpg", "path/to/preview.jpg")Extract the JpgFromRaw image (found in some RAW images):
exiftool.extractJpgFromRaw("path/to/image.cr2", "path/to/fromRaw.jpg")Extract the binary value from "tagname" tag in path/to/image.jpg
and write it to dest.bin (which cannot exist already
and whose parent directory must already exist):
exiftool.extractBinaryTag("tagname", "path/to/file.exf", "path/to/dest.bin")Note that only a portion of tags are writable. Refer to the documentation and look under the "Writable" column.
If you apply malformed values or ask to write to tags that aren't
supported, the returned Promise will be rejected.
Only string and numeric primitive are supported as values to the object
Write a comment to the given file so it shows up in the Windows Explorer Properties panel:
exiftool.write("path/to/file.jpg", { XPComment: "this is a test comment" })Change the DateTimeOriginal, CreateDate and ModifyDate tags (using the AllDates shortcut) to 4:56pm UTC on February 6, 2016:
exiftool.write("path/to/file.jpg", { AllDates: "2016-02-06T16:56:00" })If you edit a timestamp tag, realize that the difference between the
changed timestamp tag and the GPS value is used by exiftool-vendored to
infer the timezone.
In other words, if you only edit the CreateDate and don't edit the GPS
timestamps, your timezone will either be incorrect or missing. See the
section about Dates below for more information.
You may find that some of your images have corrupt metadata, and that writing new dates, or editing the rotation information, for example, fails. ExifTool can try to repair these images by rewriting all the metadata into a new file, along with the original image content. See the documentation for more details about this functionality.
rewriteAllTags returns a void Promise that will be rejected if there are any
errors.
exiftool.rewriteAllTags("problematic.jpg", "rewritten.jpg")Remember to call .end().
ExifTool processes consume system resources. If you're done with it, turn
it off with .end(), which returns a Promise<void> if you want to wait
for the shutdown to be complete.
If you use mocha v4 or later, and you don't call
exiftool.end(), you will find that your test suite hangs. The relevant
change is described here,
and can be solved by adding an after block that shuts down the instance
of ExifTool that your tests are using:
after(() => exiftool.end()) // assuming your singleton is called `exiftool`Generally, EXIF tags encode dates and times with no timezone offset. Presumably the time is captured in local time, but this means parsing the same file in different parts of the world results in a different absolute timestamp for the same file.
Rather than returning a Date which always includes a timezone, this library returns classes that encode the date, the time of day, or both, with an optional tzoffset. It's up to you, then, to do what's right.
In many cases, though, a tzoffset can be determined, either by the composite
TimeZone tag, or by looking at the difference between the local
DateTimeOriginal and GPSDateTime tags. GPSDateTime is present in most
smartphone images.
If a tzoffset can be determined, it is encoded in all related ExifDateTime
tags for those files.
Note also that some smartphones record timestamps with microsecond precision (not just millis!),
and both ExifDateTime and ExifTime have floating point milliseconds.
Official EXIF tag names
are PascalCased, like
AFPointSelected and ISO. ("Fixing" the field names to be camelCase, would
result in ungainly aFPointSelected and iSO atrocities).
The Tags interface is autogenerated by the mktags
script, which parses through over 6,000 unique camera make and model images, in
large part sourced from the ExifTool site. mktags groups tags, extracts their
type, popularity, and example values such that your IDE can autocomplete.
For an example of a group of tags, see the EXIFTags interface.
Tags marked with "★★★★", like MIMEType, should be found in most files. Of the several thousand metadata tags, realize less than 50 are found generally. You'll need to do your own research to determine which tags are valid for your uses.
Note that if parsing fails (for, example, a datetime string), the raw string will be returned. Consuming code should verify both existence and type as reasonable for safety.
The npm run mktags target reads all tags found in a batch of sample images and
parses the results.
Using exiftool-vendored:
Read 2236 unique tags from 3011 files.
Parsing took 16191ms (5.4ms / file) # win32, core i7, maxProcs 4
Parsing took 27141ms (9.0ms / file) # ubuntu, core i3, maxProcs 1
Parsing took 12545ms (4.2ms / file) # ubuntu, core i3, maxProcs 4Using the exiftool npm package takes 7x longer (and doesn't work on Windows):
Reading 3011 files...
Parsing took 85654ms (28.4ms / file) # ubuntu, core i3Starting the perl version of ExifTool is expensive, and is especially expensive on the Windows version of ExifTool.
On Windows, for every invocation, exiftool installs a distribution of
Perl and extracts the ~1000 files that make up ExifTool, and then runs
the perl script. Windows virus scanners prevent reads on these files while they
are scanned, which makes this approach even more costly.
Using ExifTool's -stay_open batch mode means we can reuse a single
instance of ExifTool across many requests, dropping response latency
dramatically as well as reducing system load.
To avoid overwhelming your system, the exiftool singleton is configured with a
maxProcs set to a quarter the number of CPUs on the current system (minimally
1); no more than maxProcs instances of exiftool will be spawned. If the
system is CPU constrained, however, you may want a smaller value. If you have
very fast disk IO, you may see a speed increase with larger values of
maxProcs, but note that each child process can consume 100 MB of RAM.
See the CHANGELOG on github.
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