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Exif Jpeg header manipulation tool

Things jhead can extract from an Exif jpeg file:

* Time and date picture was taken
* Camera make and model
* Integral low-res Exif thumbnail
* Shutter speed
* Camera F-stop number
* Flash used (yes/no)
* Distance camera was focused at
* Focal length and calculate 35 mm equivalent focal length
* Image resolution
* GPS info, if stored in image
* IPTC header
* XMP data

Things jhead can modify in an exif jpeg file:

* Up-right images according to rotation tag using jpegtran
* Set or relative adjust internal exif timestamps
* Fix date / time offsets in large batches of images
* Re-name or date stamp files according to exif timestamp
* Transfer exif headers between images
* Replace thumbnails inside Exif headers
* Edit jpeg comments (but not the Exif comments)
* Delete exif or comment sections from jpeg images
* Create new minimal exif header containing date and thumbnail

The files coming out of a pretty much all Digital cameras are in the Exif flavour of Jpeg files. Exif files are for the most part Jpeg files, but start with a different header block, and contain additional data sections with camera settings, as well as a preview thumbnail picture as part of the Exif header. Many image browsers today make use of this integral thumbnail when browsing, while other browsers make their own thumbnails based on the image as a whole.

Because I am interested in photography, I am always curious just exactly what settings my fully automatic digital camera actually did end up using. Back in 1999, when I originally wrote jhead, I couldn't find a program that would consistently display the settings, nor one that could be compiled into a simple executable. I have since added many more features to jhead, many of them the result of suggestions or code contributions.

Though there are many programs out there now that can manipulate Exif headers today, for many tasks, jhead remains the simplest and most effective tool for the job, especially if used for automated or scripted tasks.

The program also has a lot of other command line options for manipulating Exif files, such as options to manipulate the date in the header, renaming image files, or coordinating running Jpegtran and Mogrify to manipulate whole directory trees of images.

For novice Linux/Unix/OS-X users: Don't forget to set the executable bit after downloading the pre-built executables. Type "chmod +x jhead" at a shell window after downloading it to do this.