ExifTool - Enhanced Java Integration for Phil Harvey's ExifTool.

Description

The goal and main features of this fork did not changed, so this description is the same as the original library

This project represents the most robust Java integrations with Phil Harvey's excellent ExifTool available.

The goal of this project was to provide such a tight, well designed and performant integration with ExifTool that any Java developer using the class would have no idea that they weren't simply calling into a standard Java library while still being able to leverage the unmatched robustness of ExifTool.

All concepts of external process launching, management, communication, tag extraction, value conversion and resource cleanup are abstracted out by this project and all handled automatically for the caller.

Even when using ExifTool in "daemon mode" via the -stay_open True command line argument, this project hides all the details required to make that work, automatically re-using the daemon process as well as eventually cleaning it up automatically along with supporting resources after a defined interval of inactivity so as to avoid resource leaks.

The set of EXIF tags supported out of the box is based on the EXIF tags supported by the most popular mobile devices (iPhone, Android, BlackBerry, etc.) as well as some of the most popular cameras on the market (Canon point and shoot as well as DSLR).

And lastly, to ensure that integration with the external ExifTool project is as robust and seamless as possible, this class also offers extensive pre-condition checking and error reporting during instantiation and use.

For example, if you specify that you want to use stay_open support, the ExifTool class will actually check the native ExifTool executable for support for that feature before allowing the feature to be turned on and report the problem to the caller along with potential work-arounds if necessary.

Additionally, all external calls to the process are safely wrapped and reported with detailed exceptions if problems arise instead of just letting unknown exceptions bubble up from the unknown system depths to the caller.

All the exceptions and exceptional scenarios are well-documented in the Javadoc along with extensive implementation details for anyone wanting to know more about the project.

History

This library is a fork of https://github.com/rkalla/exiftool adding new features:

• Use Java executor framework (available with JDK6), instead of legacy java.utilTimer.
• ExifTool instance now implement Closeable interface (and can be used with Java 7 try-with-resource).
• Allow extensions: extracting custom tag is now allowed (just need to implement Tag interface, most common tags are still available out of the box).
• Use cache to extract ExifTool version when an instance is created.
• ExifTool is now thread-safe.
• Integration with slf4j and log4j.

More informations below.

Support

This library is tested against Java >= 7, Linux and Windows.

Installation

This library is available on maven repository:

<dependency>
  <groupId>com.github.mjeanroy</groupId>
  <artifactId>exiftool-lib</artifactId>
  <version>2.6.0</version>
</dependency>

Breaking Changes

• Tag class is now com.thebuzzmedia.exiftool.Tag, commons tags available in com.thebuzzmedia.exiftool.core.StandardTag enum class.
• Format class is now com.thebuzzmedia.exiftool.Format, commons formats (NUMERIC, HUMAN_READABLE) available in com.thebuzzmedia.exiftool.core.StandardFormat enum class.
• UnsupportedFeatureException class is now com.thebuzzmedia.exiftool.exceptions.UnsupportedFeatureException.
• Feature class has been removed, use enableStayOpen method on ExifToolBuilder class.
• Introduction of ExifToolBuilder to create instances of ExifTool.
• Use Java executor framework:
  • Thread name cannot be defined (previously named as ExifTool Cleanup Thread).
  • Old timer implementation is still here, but this is not the default used implementation.
• Thread Safety.

Examples

Parsing tags

// src/test/java/com/thebuzzmedia/exiftool/readme/basic/ExifParser.java

package com.thebuzzmedia.exiftool.readme.basic;

import com.thebuzzmedia.exiftool.ExifTool;
import com.thebuzzmedia.exiftool.ExifToolBuilder;
import com.thebuzzmedia.exiftool.Tag;
import com.thebuzzmedia.exiftool.core.StandardTag;

import java.io.File;
import java.util.Arrays;
import java.util.Map;

public class ExifParser {
  public static Map<Tag, String> parse(File image) throws Exception {
    // ExifTool path must be defined as a system property (`exiftool.path`),
    // but path can be set using `withPath` method.
    try (ExifTool exifTool = new ExifToolBuilder().build()) {
      return exifTool.getImageMeta(image, Arrays.asList(
          StandardTag.ISO,
          StandardTag.X_RESOLUTION,
          StandardTag.Y_RESOLUTION
      ));

    }
  }

  public static void main(String[] args) throws Exception {
    for (String image : args) {
      System.out.println("Tags: " + ExifParser.parse(new File(image)));
    }
  }
}

Stay Open

If you want to reuse your exiftool process, you may want to activate the stay_open feature: note that an instance of UnsupportedFeatureException will be thrown your exiftool version is too old.

// src/test/java/com/thebuzzmedia/exiftool/readme/stayopen/ExifParser.java

package com.thebuzzmedia.exiftool.readme.stayopen;

import com.thebuzzmedia.exiftool.ExifTool;
import com.thebuzzmedia.exiftool.ExifToolBuilder;
import com.thebuzzmedia.exiftool.Tag;
import com.thebuzzmedia.exiftool.core.StandardTag;
import com.thebuzzmedia.exiftool.exceptions.UnsupportedFeatureException;

import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.Map;

public class ExifParser {

  private static final ExifTool exifTool = detect();

  private static ExifTool detect() {
    try {
      return new ExifToolBuilder().enableStayOpen().build();
    } catch (UnsupportedFeatureException ex) {
      // Fallback to simple exiftool instance.
      return new ExifToolBuilder().build();
    }
  }

  public static Map<Tag, String> parse(File image) throws IOException {
    return exifTool.getImageMeta(image, Arrays.asList(
        StandardTag.ISO,
        StandardTag.X_RESOLUTION,
        StandardTag.Y_RESOLUTION
    ));
  }

  public static void main(String[] args) throws Exception {
    try {
      for (String image : args) {
        System.out.println("Tags: "+ ExifParser.parse(new File(image)));
      }
    } finally {
      exifTool.close();
    }
  }
}

Multithreading

ExifTool is completely thread-safe. It means that if you use a "stay open" process, each access (get / set meta-data) will be synchronized. This can be a big problem if you need to manipulate images in parallel. In this case, a pool can be configured to allow a maximum number of exiftool to be open.

// src/test/java/com/thebuzzmedia/exiftool/readme/multithread/ExifParser.java

package com.thebuzzmedia.exiftool.readme.multithread;

import com.thebuzzmedia.exiftool.ExifTool;
import com.thebuzzmedia.exiftool.ExifToolBuilder;
import com.thebuzzmedia.exiftool.Tag;
import com.thebuzzmedia.exiftool.core.StandardTag;

import java.io.File;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ExifParser {

  private static final ExifTool exifTool = detect();

  private static ExifTool detect() {
    return new ExifToolBuilder()
        .withPoolSize(10)  // Allow 10 process
        .enableStayOpen()
        .build();
  }

  public static Map<Tag, String> parse(File image) throws Exception {
    try (ExifTool exifTool = new ExifToolBuilder().build()) {
      return exifTool.getImageMeta(image, Arrays.asList(
          StandardTag.ISO,
          StandardTag.X_RESOLUTION,
          StandardTag.Y_RESOLUTION
      ));

    }
  }

  private static Map<Tag, String> parse(String image) throws Exception {
    return parse(new File(image));
  }

  public static void main(String[] args) throws Exception {
    ExecutorService executor = Executors.newFixedThreadPool(10);

    try {
      for (final String image : args) {
        executor.submit(new Runnable() {
          @Override
          public void run() {
            try {
              System.out.println("Tags: " + parse(image));
            }
            catch (Exception ex) {
              ex.printStackTrace();
            }
          }
        });
      }
    } finally {
      executor.shutdown();
      exifTool.close();
    }
  }
}

Performance

You can benchmark the performance of this ExifTool library on your machine by running the Benchmark class under the /test/java repository.

Here is an example output on my Core2 Duo 3.0Ghz E6850 w/ 12GB of Ram:

Benchmark [tags=49, images=10, iterations=25] 250 ExifTool process calls, 12250 total operations.

[-stay_open False]
	Elapsed Time: 97823 ms (97.823 secs)
[-stay_open True]
	Elapsed Time: 4049 ms (4.049 secs - 24.159792x faster)

You can see that utilizing the -stay_open functionality provided in ExifTool you can realize magnitudes times more performance.

Also the bigger of a test you run (more iterations) the bigger the performance margin increases.

Troubleshooting

Below are a few common scenarios you might run into and proposed workarounds for them.

• I keep getting UnsupportedFeatureException exceptions when running ExifTool stay_open support.

This exception will only be raised when you attempt to use a feature that the underlying ExifTool doesn't support. This means you either need to upgrade your install of ExifTool or skip using the feature.

• I downloaded the newest version of ExifTool, but I keep getting UnsupportedFeatureExceptions.

What is probably happening is that your host system already had ExifTool installed and the default EXIF_TOOL_PATH is simply running the command "exiftool" which executes the one in the system path, not the newest version you may have just downloaded.

You can confirm this by typing 'which exiftool' to see which one is getting launched. You can also point the ExifTool class at the correct version by setting the path of the exiftool executable to use.

• Can the ExifTool class support parsing InputStreams instead of File representations of images?

No. Phil has mentioned that enabling daemon mode disables the ability to stream bytes to ExifTool to process for EXIF data (because ExifTool listens on the same input stream for processing commands and a terminating -execute sequence, it can't also listen for image byte[] data).

Because of this and because of the expectation that ExifTool in daemon mode will be the primary use-case for this class, limited support for InputStream parsing was designed out of this class.

• Do I need to manually call close() to cleanup a daemon ExifTool?

This is done automatically for you when exifTool instance is garbage collected or via the cleanup thread the class employs when a daemon instance of ExifTool is created. Unless you modified the delay of the cleanup thread (and set it to 0 or less), the automatic cleanup thread is enabled and will clean up those resources for you after the specified amount of inactivity.

Nevetheless, I suggest you to use exiftool with a try-with-resource and to force close operation when your program stops.

Reference

• ExifTool by Phil Harvey - http://www.sno.phy.queensu.ca/~phil/exiftool/
• imgscalr - https://github.com/rkalla/imgscalr

License

This library is released under the Apache 2 License. See LICENSE.