@xoi/gps-metadata-remover

@xoi/gps-metadata-remover

Frontend-friendly Javascript package that removes GPS metadata from images and videos

Takes a photo or video file and writes over in-place where GPS metadata is detected. Removes Exif from images and various forms of GPS metadata from videos.

Currently compatible with JPG, PNG, TIF, MOV, MP4

Installation

yarn add @xoi/gps-metadata-remover or npm i @xoi/gps-metadata-remover

Usage

removeLocation is the main removal function, although some other utility functions are provided in the index to help read in data correctly if needed. This is how the package looks being used in react native with react-native-fs:

import { removeLocation, base64StringToArrayBuffer } from '@xoi/gps-metadata-remover'

const read = async (size, offset) => {
  const base64Data = await rnfs.read(destPath, size, offset, 'base64')
  return base64StringToArrayBuffer(base64Data)
}
const write = async (writeValue, entryOffset, encoding) => {
  await rnfs.write(destPath, writeValue, entryOffset, encoding)
}
const gpsWasRemoved = await removeLocation(destPath, read, write)

removeLocation returns true if GPS metadata was found and rewritten and false if no GPS metadata was found and nothing was rewritten.

This package is platform-agnostic, so the client is expected to pass in filesystem read and write functions that work for their platform. The functions should match the following types:

export type ReadFunction = (size: number, offset: number) => Promise<Buffer>

export type WriteFunction = (writeValue: string, entryOffset: number, encoding: string) => Promise<void>

XMP Removal

One of the metadata formats from which this package removes metadata is Adobe's XMP.

Currently, if it finds XMP metadata in a file, this package simply wipes the whole of the XMP block rather than just the GPS metadata in that block; this code was originally written under a bit of a time crunch and removing all of the XMP was acceptable since we don't use XMP at all.

If you need to leave XMP intact, pass the optional options parameter object to removeLocation with skipXMPRemoval set to true:

const gpsWasRemoved = await removeLocation(destPath, read, write, { skipXMPRemoval })

At some point I'll write (or accept a PR for) the logic to properly find and remove just the GPS from XMP and leave the rest.

Testing

nodeStripContent.js is a node utility that takes a file name, source directory, and destination directory, copies the file from the source to destination directory, and performs the metadata stripping operation on the file in the destination directory, the result of which can then be compared to the original.

There is a command-line wrapper script around this called batchRemoveMetadata.js that takes an in-directory and out-directory and performs this operation on all file in the in-directory, so a batch of files can manually have GPS removed. This can be run with yarn batch-remove-content

There is also a jest suite around nodeStripContent.js providing the tests which all new commits must pass. When this was an internal tool, this was designed to be used with an s3 bucket to which all XOi devs have access. In open-sourcing this library, I've included a smaller set of test content instead since everything will instead need to be checked in to git. The test suite runs content stripping against unprocessed files and compares them to previously verified processed files and ensures consistent operation each time, as well as testing for corruption and visual correctness for images. The tester can also add new content to the test collection. Manually run content with the batch remover, manually check for visual correctness and metadata removal, then add the unprocessed file to the corresponding preprocessed and the processed to processed-clean for its filetype.

Note that to run the jest tests you must brew install graphicsmagick on your machine.