Windows / Mac users: Jhead has no Graphical User Interface. Clicking on it with the mouse from Windows or Mac OS-X won't do anything for you - you have to use it from the Command prompt (or DOS prompt under Win95/98)
| -autorot |
Using the 'Orientation' tag of the Exif header, rotate the image so that it is upright.
The program 'jpegtran' is used to perform the rotation. This program is present in most
Linux distributions. For windows, you need to get a copy of it.
After rotation, the orientation tag of the Exif header is set to '1' (normal orientation).
The thumbnail is not rotated (that would be much harder). Other fields of the Exif header,
including dimensions are untouched, but the JPEG height/width are adjusted. This feature is especially useful with newer Canon cameras, that set the orientation tag automatically using a gravity sensor. | ||||||||||||||||||||
| -norot | Clears the Exif header rotation tag without altering the image. You may find that your images have rotation tags in them from your camera, but you already rotated them with some lossless tool without clearing the rotation tag. Now your friendly browser rotates the images on you again because the image rotation tag still indicates the image should be rotated. Use this option to fix this problem. | ||||||||||||||||||||
| -dt | Delete thumbnails from the Exif header, but leave the interesting parts intact. This option truncates the thumbnail from the Exif header, provided that the thumbnail is the last part of th Exif header (which so far as I know is always the case). Exif headers have a built-in thumbnail, which typically occupies around 10k of space. This thumbnail is used by digital cameras. Windows XP may also use this thumbnail if present (but it doesn't need it). The thumbnails are too small to use even full screen on the digicam's LCD. I have not encountered any adverse side effects of deleting the thumbnails, even from the software provided with my old Olympus digicam. Use with caution. | ||||||||||||||||||||
| -de | Delete the Exif header entirely. This leaves comments in the comment section intact. | ||||||||||||||||||||
| -dc | Delete comment field from the JPEG header. Note that the comment is not part of the Exif header. | ||||||||||||||||||||
| -du | Delete sections of jpeg that are not Exif, not comment, and otherwise not contributing to the image either - such as data that photoshop might leave in the image. | ||||||||||||||||||||
| -purejpg | Delete all JPEG sections that aren't necessary for rendering the image. Strips any metadata that various applications may have left in the image. A combintion of the -de -dc and -du options. | ||||||||||||||||||||
| -ce |
Edit the JPEG header comment field (note, this comment field is outside the Exif structure
and can be part of Exif and non Exif style JPEG images).
A temporary file containing the comment is created and a text editor is launched to edit the file. The editor is specified in the EDITOR environment variable. if none is specified notpead or vi are used under Windows and Unix respectively. After the editor exits, the data is transferred back into the image, and the temporary file deleted. | ||||||||||||||||||||
| -cs <name> | Save comment section to a file | ||||||||||||||||||||
| -cl <comment> | Replace comment with comment from command line. | ||||||||||||||||||||
| -ci <name> | Replace comment with text from file. | ||||||||||||||||||||
| -st <name> |
Save the built in thumbnail from Jpegs that came from a digital camera. The thumbnail lives
inside the Exif header, and is a very low-res JPEG image. Note that making
any changes to a photo, except for with some programs, generally wipes out the Exif header
and with it the thumbnail.
I implemented this option because I kept getting asked about having such an option. I don't consider the built in thumbnails to be all that useful - too low res. However, now you can see for yourself. I always generate my thumbnails using ImageMagick (see end of this page). This feature has an interesting 'relative path' option for specifying the thumbnail name. Whenever the <name> contains the characters '&i', jhead will substitute the original filename for this name. This allows creating a 'relative name' when doing a whole batch of files. For example, the incantation:
If a '-' is specified for the output file, the thumbnail is sent to stdout. (Unix build only) | ||||||||||||||||||||
| -te <name> |
Transplant Exif header from image <name> into specified image. This option is
useful if you like to edit the photos but still want the Exif header on your photos.
As most photo editing programs will wipe out the Exif header, this option can be used
to re-transmplant them back in after editing the photos.
Like the '-st' option, this option uses a 'relative path', which is useful for doing a batch of photos at a time. For example, if you have a directory full of digital camera photos, before editing them, you could copy them into the subdirectory 'originals. Then edit them (or batch convert them using mogrify). After editing, you can put the original Exif headers back in to the whole directory of images at a time using the incantation:
| ||||||||||||||||||||
| -h | Displays summary of command line options. | ||||||||||||||||||||
| -v | Makes the program even more verbose than it already is. Like DOS programs, and unlike Unix programs, Jhead gives feedback as to what it is doing, even when nothing goes wrong. Windows user that I am, when something doesn't give me feedback for 20 seconds, I assume its crashed. | ||||||||||||||||||||
| -se | Suppress error messages relating to corrupt Exif header structure. | ||||||||||||||||||||
| -V | Print version info and compilation date. | ||||||||||||||||||||
| -c | Concise output. This causes picture info to be summarized on one line instead of several. Useful for grepping through images, as well as importing into spread sheets (data is space delimited with quotes as text qualifier). | ||||||||||||||||||||
| -model |
Restricts processing of files to those whose camera model, as indicated by the Exif image
information, contains the substring specified in the argument after '-model'.
For example, the following command will list only images that are from an S100 camera:
jhead -model S100 *.jpg
I use this option to restrict my JPEG re-compressing to those images that came from my Cannon S100 digicam, (see the -cmd option).
| ||||||||||||||||||||
| -exonly |
Skip all files that don't have an Exif header. This skips all files that did not
come directly from the digital camera, as most photo editing software does not
preserve the Exif header when saving pictures.
| ||||||||||||||||||||
| -n[fmt-string] |
This option causes files to be renamed according to the Exif header "DateTimeOriginal" field.
If the file is not an Exif file, or the DateTimeOriginal does not contain a valid value,
the file date is used.
Renaming is by default restricted to files whose names consist largely of digits.
This effectively restricts renaming to files that have not already been manually renamed, as
the default sequential names from digital cameras consist largely of digits.
Use the -nf option to force renaming of all files.
If the [fmt-string] is omitted, the file will be renamed to MMDD-HHMMSS. Note that
this scheme doesn't include the year (I never have photos from different years together anyway).
Some of the more useful arguments for strftime are:
Example: This will rename files matched by *.jpg according to YYYYMMDD-HHMMSS For a full listing of strftime arguments, look up the strftime function. Note that some arguments to the strftime function (not listed here) produce strings with characters such as '/' and ':' that may not be valid as part of a filename on various systems. | ||||||||||||||||||||
| -nf |
Same as '-n' but renames files regardless of original file name.
| ||||||||||||||||||||
| -ta |
Adjust time stored in the Exif header by h:mm backwards of forwards. Useful when having
taken pictures with the wrong time set on the camera, such as after travelling across
time zones, or when daylight savings time has changed.
This option uses the time from the "DateTimeOriginal" (tag 0x9003) field, but sets
all the time fields in the Exif header to the new value. Version 2.0 and earlier only
modified the "DateTimeOriginal" (tag 0x9003) field, but too many people thought
that that was a bug.
Examples: Adjust time one hour forward (you would use this after you forgot to set daylight savings time on the digicam)
| ||||||||||||||||||||
| -ts |
Sets the time stored in the Exif header to what is specified on the command line.
This option changes all the date fields in the Exif header. Version 2.0 and earlier
only changed the "DateTimeOriginal" (tag 0x9003) field, but too many people thought
this was a bug. Time must be specified as: yyyy:mm:dd-hh:mm:ss
| ||||||||||||||||||||
| -ft | Sets the file's system time stamp to what is stored in the Exif header. | ||||||||||||||||||||
| -cmd |
Executes the specified command on each Jepg file to be processed. The Exif section of each file is read before running the command, and re-inserted after the command finishes. The specified command invoked separately for each JPEG that is processed, even if multiple files are specified (explicitly or by wild card). I use this option to process whole directory trees of Jpegs from my digital camera with JPEGTRAN (Independent JPEG group) and Image-Magic's 'MOGRIFY' command without loosing the camera settings and other info stored in the Exif headers. JPEGTRAN is useful for lossless rotation, as well as for converting Jpegs to progressive Jpegs (also a lossless process, but results in typically 5% smaller files) I use mogrify for re-compressing the images I get from my Canon PowerShot S100 to 80% quality. The Canon Jpegs are either way too 'high quality' for the resolution, or are suboptimally encoded. Using mogrify to 80% produces no detectable loss in quality, with files about half the size.
Example use:
jhead -cmd "jpegtran -progressive &i &o" -r *.jpg
Keeping the Exif header information is important to me, as I like to check things like the shutter speed for some of my photos, and my HTML index generating program uses the Exif tags to display the JPEG images in order of taking. Newer version of "mogrify" already preserve Exif information, so with some clever shell scripting, you could do these two steps without using jhead and still keep the Exif headers.
| ||||||||||||||||||||
| -r | The recursive feature of version 1.0 never worked to my satisfaction, and I replaced it with my recursive file globbing code in the Windows version. See below. |
Modifying of Exif header data is very limited, as Jhead internally only has a read only implementation of the file system contained in the Exif header. For example, there is no way to replace the thumbnail or edit the Exif comment in the Exif header. There is also no way to create minimal exif headers.
Some Canon digital SLR cameras fail to encode the effective sensor resolution when shooting at less than full resolution, causing jhead to incorrectly miscalculate the 35mm equivalent focal length. Jhead usually gets blamed for this bug, but it is in fact a camera bug, and jhead can't do much about it.
jhead c:\pix\199*\*\*.jpg
This program goes one step beyond beyond that in that "**" as a path component means any level of subdirectories. The invocation
jhead c:\**\*.jpg
will find ALL Jpegs files on the c: drive, including those in the root directory. The ** only works if it is the only part of that path component. For example, the path 'c:\a**\*.jpg' will not recurse. The '**' recursive expansion is ONLY supported on the Windows version. The code is in the module 'myglob.c', if you want to reuse it (I certainly intend to reuse that code for other applications). Under Unix, the shell's wildcard expansion is pretty decent already, and dealing with the convoluted nature of some Unix file layouts, doing better would have been much more of a challenge.
Image Magick is one of the few programs that preserves comment and Exif headers, although older versions do not.
There's a fancier version, with pre-built Windows binaries and a lossless cropping feature added at: http://sylvana.net/jpegcrop.
Jhead homeage: http://www.sentex.net/~mwandel/jhead
Last Updateed: Dec 2004