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Embedding derived JPEG2000 image files with image technical metadata transferred from source images

Embedding derived JPEG2000 image files with image technical metadata transferred from source images

Mar 15, 2024

More and more metadata

Image capture devices (cameras, scanners) and image editing applications embed valuable technical metadata within image files. Librarians have, for quite some time, understood that basic image technical metadata elements (e.g., image bit-depth, color encoding scheme, compression, format) are critically useful to the systems and processes we've developed for preserving and managing image collections.

 

Images created by today's digital cameras – and especially cellphone cameras -- include additional metadata likely to be valuable in understanding the context and conditions within which digital images were made. The quantity and variety of these metadata elements continues to grow, and with increasing frequency includes geolocation coordinates, altitude, cardinal direction in which the camera was pointed, distance between your camera and the image's focal point, assertions of intellectual property rights, image descriptions, and...more, all in addition to detailed information about the device and device-settings used to capture the original image. This bloating store of information about our images is being read by applications designed to help us search and navigate image collections, often presenting us with automatically generated location-grouped images, time-grouped, subject-grouped, color-scheme-grouped, capture-device-grouped images, etc.

Problem

Many museums and research libraries create and collect images in common formats such as TIFF and JPEG, and later convert these images to the JPEG2000 format (JPEG 2000 Part 1, Core Coding System) for long-term preservation, and to better support online delivery. Unfortunately, the best, most robust JP2 encoding applications do not transfer much, if any, image technical metadata from source images (e.g., a group of TIFFs) to the output JP2 images.

Our solution

In the winter of 2016, Imaging Services JP2-creation scripts were modified to copy image technical metadata from source TIFF-format images to the JPEG2000 copies.

The command-line added to our JP2-generating script:

$ exiftool -ext tif -tagsfromfile @ -srcfile %f.jp2 [directory name] -XMP:format= -ImageHistory='Image technical metadata values were copied (via exiftool) from a source image to this derivative JP2 copy.' -overwrite_original

Command-line elements explained:

Sample images

:: Case 1 ::

:: Case 2 ::

:: Technical metadata values as recorded in DRS for image from Charlie Hebdo collection :: (Note: Access to metadata only available to DRS administrative account holders.)