If you’ve ever labored under the wish that you could easily extract, edit, or read that wonderful data embedded in your image files, you’re not alone.

There are lots of reasons to work with the embedded metadata in your image or other media files. For instance, you may want to keep records about your collections or display the file size and pixel dimensions of images in your collection. Much of this data exists in tags embedded in image files. Some data formats you might see in your images include EXIF, XMP, IPTC-IIM. Each format has its own set of attributes and a lot of those attributes overlap.

Screen shot of output from both tools (Exiv2 left, ExifTool right)

Part of our work with the National Digital Newspaper Program is to deliver valid metadata and image files to the Library of Congress. I recently used two command line tools to read and edit the embedded metadata in these files.

You can read and write image metadata using Photoshop but for various reasons I needed a command-line tool (you can email me if you’re interested in why). Both ExifTool and Exiv2 met my criteria:

• free
• well documented
• Unix and Windows OS compatible
• read and write multiple metadata formats
• command-line operable

Generally both were useful and required a little patience to install. Exiv2 was a breeze to install on a Windows machine but a bit trickier to build and install on a MAC OS X (using the “Source” pkg.). The full ExifTool install requires Perl but supports more metadata formats and I found that the commands were generally easier to understand and run. There is also a sort of “lite” feature where you just use drag and drop a file over the top of program file and it reads the metadata (I needed to read and write so I didn’t try this but it sounds interesting).

Conclusion: both got the job done and the differences might be negligable to most, but I seemed to prefer ExifTool for the reasons above.