@enviro/metadata v1.5.1

Node-Metadata

An advanced Node.js interface to the exiftool. 🚀

“An amazing level of senseless perfectionism, which is simply impossible not to respect.”

Exiftool is an amazing tool written by Phil Harvey in Perl which can read and write metadata to a number of file formats. This library supports streams. So, you don't have to handle anything from your end. It also cache network files to save your bandwidth.

Table of Contents

• Requirements
• API
  • Extract Metadata
  • Add/Edit Metadata
  • Copy Metadata
  • Read/Write Options
  • Cache
• Advanced
  • Custom Configuration
  • Performance
  • CLI
• Experimental Features
• Test
  • Jest
• Tools
• Known Issues
• Sponsor
• License

Install

npm install @enviro/metadata

Requirements

• Exiftool need perl to be installed on your system, Download Perl.
• Node.js version >= 16.x
• ExifTool is no longer included with this package, Download ExifTool.Read more about seamless ExifTool integration using path option in documentation.

Import & Configure

import Metadata from "@enviro/metadata";

// OPTIONAL
// only required if you are using user-defined tags
async function config() {
    await Metadata.configurator({
        default: true,
        no_cache_cleanup: true,
        tags: [
            {
                name: "CUSTOM_TAG",
                type: "string",
                exifPropGroup: "Exif",
                exifPropSubGroup: "Main",
            },
            {
                name: "CUSTOM_TAG",
                type: "string",
                exifPropGroup: "PDF",
                exifPropSubGroup: "Info",
            },
        ],
    });
}

• Options

  Name	Type	Description
  default	boolean	AdvancedDefault undefinedThe default configuration use hex keys in file. If you want to use key name in file, set this option explicitly false.
  keyCodeEvaluator	number	AdvancedThe value must be greater than 53248. This is the default key for the first user-defined tag.
  no_cache_cleanup	boolean	This will stop auto cache cleaner on node server startup.
  tags	[ExifCustomTag]	Configure Exiftool to add or remove new metadata tags to the file.

  • ExifCustomTag

    Name	Type	Description
    name	string	The name of the custom tag.
    type	"string"	Type of the custom tag's value. You can pass custom valid type in here which is supported by exif tag group.
    exifPropGroup	"Exif"|"PDF"| string	The custom tag's belongs to this group. Custom group can be passed as an argument. Read more at Family 0 (Information Type)
    exifPropSubGroup	"Main"|"Info"| string	The custom tag's belongs to this specific sub group. Custom sub-group can be passed as an argument. Read more at Family 1 (Specific Location)

API

• Extract Metadata

  • Local File

  async function read() {
      try {
          const metadata = await Metadata.get("test.pdf", {
              // path not required, since ExifTool is accessible from terminal using exiftool.
              // path: "exiftool",
              tags: [
                  {
                      name: "FileName",
                      exclude: true,
                  },
              ],
          });
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  • Output

  [
      {
          FileSize: "89 kB",
          FileModifyDate: "2022:11:11 17:08:58+05:00",
          FileAccessDate: "2022:11:11 17:08:58+05:00",
          FileInodeChangeDate: "2022:11:11 17:08:58+05:00",
          FilePermissions: "-rwxrwxrwx",
          FileType: "PDF",
          FileTypeExtension: "pdf",
          MIMEType: "application/pdf",
          PDFVersion: 1.3,
          Linearized: "No",
          Encryption: "Standard V1.2 (40-bit)",
          UserAccess:
              "Print, Copy, Annotate, Fill forms, Extract, Assemble, Print high-res",
          CreateDate: "2001:10:26 13:39:34",
          Producer: "Acrobat Distiller 4.05 for Windows",
          ModifyDate: "2001:10:26 13:40:41-04:00",
          Title: "PDF Bookmark Sample",
          Author: "Accelio Corporation",
          PageCount: 4,
      },
  ];

  FileName excluded from the result.

  • File Stream

  import { createReadStream } from "node:fs";
  
  async function streamFile() {
      try {
          const rs = createReadStream("sample.pdf");
          const metadata = await Metadata.get(rs, {
              path: "path/to/ExifTool",
          });
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  • Network Stream

  async function streamURL() {
      try {
          const metadata = await Metadata.get(
              "https://www.w3.org/WAI/ER/tests/xhtml/testfiles/resources/pdf/dummy.pdf",
              {
                  no_cache: true,
              }
          );
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  • Options

  Name	Type	Description
  fileName	string	Read: Cache file name.
  no_cache	boolean	This option doesn't work on local file path passed as a parameter. no_cache: true default for stream, read more about Stream caching. no_cache: false default for network file, read more Network stream.
  tags	[ExifReadOPTag]	Filter the output metadata tags either excluded them or only include them.
  all	boolean	Default falseIf true, all the metadata tags will be returned. This will override the tags option.NOTE: This option can cause significant performance issues. Use it only if you need all the metadata tags.
  batch	BatchReadOptions	Options for batch processing.

  • ExifReadOPTag

    Name	Type	Description
    name	string	Name of the metadata tag.
    exclude	boolean	exclude: true exclude this tag from the result. exclude: false make this tag exclusive.
    custom	string	AdvancedCustom Exiftool reading command can be directly passed to custom.Read more about exiftool commands.

  • BatchReadOptions

    Name	Type	Description
    no_network_cache	boolean|[string]	Default false.If true, the network files will not be cached. If specified list of URLs provided, than that URLs will not be cached.
    no_stream_cache	[string]	Default null.If file name is not valid for stream perspective, then that specific stream will not be cached. [] or null means all streams will be discarded after reading metadata.

• Add/Edit Metadata

  • Local File

  async function write() {
      try {
          const metadata = await Metadata.set("sample.pdf", {
              tags: [
                  {
                      name: "CUSTOM_TAG",
                      value: "custom value",
                  },
              ],
          });
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  • File Stream

  async function streamFile() {
      try {
          const rs = createReadStream("sample.pdf");
          const metadata = await Metadata.set(rs, {
              path: "path/to/ExifTool",
              tags: [
                  {
                      name: "CUSTOM_TAG",
                      value: null,
                  },
              ],
          });
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  An empty tag will delete the tag from the file.

  • Network Stream

  async function streamURL() {
      try {
          // NOTE: This pdf has a size of 26 MB
          const metadata = await Metadata.set(
              "https://research.nhm.org/pdfs/10840/10840.pdf",
              {
                  path: "path/to/ExifTool",
                  new: true,
                  prev: true,
                  tags: [
                      {
                          name: "CUSTOM_TAG",
                          value: "NEW VALUE",
                      },
                  ],
              }
          );
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

  • OUTPUT

  {
      message: 'File updated successfully!',
      // Path to the file which metadata was edited
      file: '../../dir/to/the/sample.pdf',
      // OR
      // This type of path will be generated for streams
      file: '../../path/to/dir/.tmp/0b00f9b2-cc7d-48b6-8fad-d7e2992de663'
  }

  • Options

  Name	Type	Description
  fileName	string	Custom cache file name.
  metadata	boolean	Default false.Returns the metadata of the file before modifying metadata will be returned.
  new	boolean	! Priority new > metadata.Default false.Returns the metadata of the file after modifying metadata will be returned.
  all	boolean	Default false.If true, all the metadata tags will be returned. This will override the tags option. NOTE: This option can cause significant performance issues. Use it only if you need all the metadata tags.
  delete_all	boolean	:redcircle: UNSAFE**_Default false**.If true all the metadata tags will be deleted from the file. New tags will remain unaffected.
  tags	[ExifWriteOPTag]	Add new or edit existing metadata tags to the file.

  • ExifWriteOPTag

    Name	Type	Description
    name	string	The name of the metadata tag. If it's a custom tag, make sure to initialize the Metadata.configurator()
    value	any|null	The value of the metadata tag. If the tag has no value then it will be removed from the file.
    custom	string	AdvancedCustom Exiftool writing command can be directly passed to custom.Read more about ExifTool commands.
    empty_tag	boolean	:x: DEPRECATEDDelete the current tag's value without deleting the whole tag from the file.

• Copy Metadata

  This function allows to copy the metadata from one file or directory to another file or directory.

  async function copyFromFileToStream() {
      try {
          const stream = createReadStream("/path/to/dir/img_2.jpg");
          const result = await Metadata.copy(
              "/path/to/dir/img_1.jpg",
              stream,
              {
                  path: "path/to/ExifTool",
                  src: {
                      tags: [
                          {
                              name: "Author",
                          },
                      ],
                  },
                  dst: {
                      tags: [
                          {
                              name: "Author",
                          },
                      ],
                  },
              }
          );
          console.log(JSON.stringify(result, null, 2));
      } catch (e) {
          console.error(e);
      }
  }

  The above code will copy the Author tag from image img_1.jpg and set it to img_2.jpg, but dst overrides the Author tag to be deleted. Hence, the tag will be removed from the image img_2.jpg.

• Read/Write Options

  These options can be passed to read, write, and copy methods.

  • ExifMetadataReadWriteOptions

    Name	Type	Description
    path	string	RequiredDefault 'exiftool'.The path of the ExifTool binaries.NOTE: If exiftool is callable from CLI as perl exiftool, then path is optional.
    config	string	AdvancedThe path to the config file to use with exiftool.
    del_cache_on_error	boolean	Default falseIf true, the temporary file will be deleted if an error occurs.Recommended to use with stream cache.
    stream	boolean	AdvancedDefault false.If true, instead of returning metadata in a JSON compatible object, an instance of readable stream containing metadata string will be returned.NOTE: This option will return raw metadata instead of JSON, custom parser will be required to parse JSON. JSON.parse() will always throw an error with fast: true.

Cache

• Manually remove all cache.

Metadata.clear();

• Disable network caching.

async function streamURL() {
    const metadata = await Metadata.get("https://example.com/imagine.pdf", {
        no_cache: true,
    });
    console.log(metadata);
}

Explicitly set no_cache: true to disable caching for network file.

• Enable stream caching.

async function streamFile() {
    const rs = createReadStream("sample.pdf");
    const metadata = await Metadata.get(rs, {
        no_cache: false,
    });
}

Explicitly set 'no_cache' to false to enable caching for stream.

Advanced

• Custom Configuration

  If Metadata.configurator does not meet the requirements. You can provide a custom configuration file with Metadata.get() or Metadata.set() function options.

  • sample.cfg

  # Example config file
  %Image::ExifTool::UserDefined = (
      'Image::ExifTool::Exif::Main' => {
          d000 => {
              Name => 'CUSTOM_TAG',
              Writable => 'string',
          },
      },
      'Image::ExifTool::PDF::Info' => {
          CUSTOM_TAG => {
              Name => 'CUSTOM_TAG',
              Writable => 'string',
          },
      },
  );
  1; #end

  Read more: https://exiftool.org/config.html

  • Use custom configuration

  async function read() {
      try {
          const metadata = await Metadata.get("image.jpg", {
              config: "../path/to/sample.cfg",
          });
          console.log(metadata);
      } catch (e) {
          console.error(e);
      }
  }

• Custom cache file name

  This library does not support caching for stream passed as a parameter in such case you should provide something that could identify the cache file later. If you do not provide a cache file name a random name will be generated.no_cache: false will be ignored for stream passed as a parameter, if fileName is not provided.

  import { createReadStream } from "node:fs";
  
  const rs = createReadStream("sample.pdf");
  const metadata = await Metadata.get(rs, {
      fileName: "sample.pdf",
      no_cache: false,
  });
  console.log(metadata);

• Performance

  There is a significant overhead in loading ExifTool, so performance may be greatly improved by taking advantage of ExifTool's batch processing capabilities.

  • Batch Processing

    This allows to process multiple files in one function call, and helps to reduce the startup overhead. Sample batch processing code can be found in the examples/batch directory.

  • Read Metadata

    async function readMultipleFromDisk() {
        try {
            const metadata = await Metadata.get([
                "/path/to/dir/samples/img_1.jpg",
                "/path/to/dir/samples/img_2.jpg",
                ...
            ]);
            console.log(metadata);
        } catch (e) {
            console.error(e);
        }
    }

  • Edit/Write Metadata

    async function writeMultipleFromDirectory() {
        try {
            const metadata = await Metadata.set("../../path/to/dir", {
                new: true,
                metadata: true,
                tags: [
                    {
                        name: "Author",
                        value: "John Doe",
                    },
                ],
            });
            console.log(JSON.stringify(metadata, null, 4));
        } catch (e) {
            console.error(e);
        }
    }

• CLI

  To execute complex or direct access to ExifTool use CLI method.

  const command = `-j ~/path/to/file`;
  const subscriberId = Metadata.CLI.run(command || commands, (err, data) => {
          console.log(err || data);
          Metadata.CLI.stop(subscriberId);
      }, {
          path: exifToolPath
      });

  • :warning: NOTE: If the command contains arbitrary spaces, use array syntax to avoid confusion.Example:

  const command = [
      '-j',
      '-Author="Foo Bar"',
      '"~path/to/file/containing spaces/file name.pdf"'
  ]

  Remove CLI events listener

  Remove the current CLI events listener once the task is finished to avoid receiving metadata for additional CLI tasks. Use "queue" option, which will handle everything for you.

  Metadata.CLI.stop(subscriberId);

  Exit CLI

  This will automatically terminate the CLI process and all events listeners.

  Metadata.CLI.kill();

  More examples: examples/raw.js

  • Options

  Name	Type	Description
  path	string	RequiredThe path to the ExifTool binary.NOTE: path is optional, if ExifTool is callable from the CLI as perl exiftool.
  config	string	The configuration file path.
  raw	boolean	AdvancedDefault falseIf true, the child process will be returned.
  streams	boolean	AdvancedDefault falseIf true, raw streams will be returned.
  queue	boolean	AdvancedDefault falseIf true, the stream observer will serve streams in queued order and will remove the callback from the stream observer once the command is fulfilled successfully or not.

• :warning: Experimental Features

  Experimental features can be unstable or maybe subject to change, using them in a production environment is not recommended.

  Name	Type	Description
  fast	boolean	AdvancedDefault falseIf true, a dedicated process will be started for the binaries. This can significantly increase performance.To exit fast mode, use Metadata.stop();

NOTE

• The package is pure ESM. It cannot be require() from CommonJS.
• Future version might break backward compatibility.
• Check release notes for breaking changes.

Future

• This library is currently rewritten in TypeScript.
• fast mode will be enabled by default.

Examples

Examples can be found inside example directory.

Tools

• Comming Soon

Known Issues

If you discover any bug, create an issue.

Sponsor

Support this project.

License

MIT