JHEAD(1)                   OpenBSD Reference Manual                   JHEAD(1)



NAME
       jhead - Digicam JPEG Exif header manipulation tool

SYNOPSIS
       jhead [ options ] [ file...  ]


DESCRIPTION
       jhead is used to display and manipulate data contained in the Exif
       header of JPEG images from digital cameras.  By default, jhead displays
       the more useful camera settings from the file in a user-friendly
       format.

       jhead can also be used to manipulate some aspects of the image relating
       to JPEG and Exif headers, such as changing the internal timestamps,
       removing the thumbnail, or transferring Exif headers back into edited
       images after graphical editors deleted the Exif header.  jhead can also
       be used to launch other programs, similar in style to the UNIX find
       command, but much simpler.



GENERAL METADATA OPTIONS
       -te file
              Transplant Exif header from a JPEG (with Exif header) in file
              into the image that is manipulated.  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-copy them back from
              original copies after editing the photos.


              This feature has an interesting 'relative path' option for
              specifying the thumbnail name.  Whenever the <name> contains the
              characters '&i', will substitute the original  filename for this
              name. This allows creating a jhead 'relative name' when doing a
              whole batch  of files. For example, the incantation:

              jhead -te originals/&i *.jpg

              would transfer the exif header for each .jpg file in the
              originals directory by the same name, Both Win32 and most Unix
              shells treat the command line option for the '&' to even be
              passed to the program.


       -dc    Delete comment field from the JPEG header.  Note that the
              comment is not part of the Exif header.

       -de    Delete the Exif header entirely.  Leaves other metadata sections
              intact.

       -di    Delete the IPTC section, if present.  Leaves other metadata
              sections intact.

       -dx    Delete the XMP section, if present.  Leaves other metadata
              sections intact.

       -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 combination of the -de -dc and -du
              options.

       -mkexif
              Creates minimal exif header. Exif header contains date/time, and
              empty thumbnail fields only. Date/time set to file time by
              default. Use with -rgt option if you want the exif header to
              contain a thumbnail. Note that exif header creation is very
              limited at this time, and no other fields can be added to the
              exif header this way.

       -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 notepad
              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 file
              Save comment section to a file

       -ci file
              Replace comment with text from file

       -cl string
              Replace comment with specified string from command line file


DATE / TIME MANIPULATION OPTIONS
       -ft    Sets the file's system time stamp to what is stored in the Exif
              header.

       -dsft  Sets the Exif timestamp to the file's timestamp. Requires an
              Exif header to pre-exist. Use -mkexif option to create one if
              needed.

       -n[format_string]
              This option causes files to be renamed and/ or mmoved using the
              date information from 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 new name
              contains a '/', this will be interpreted as a new path, and the
              file will be moved accordingly.

              If the format_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).

              If a format_string is provided, it will be passed to the
              strftime function as the format string.  In addition, if the
              format string contains '%f', this will substitute the original
              name of the file (minus extension).  '%i' will substitute a
              sequence number.  Leading zeros can be specified like with
              printf - i.e. '%04i' pads the number to 4 digits using leading
              zeros.

              If the name includes '/', this is interpreted as a new path for
              the file.  If the new path does not exist, the path will be
              created.

              If the target name already exists, the name will be appended
              with "a", "b", "c", etc, unless the name ends with a letter, in
              which case it will be appended with "0", "1", "2", etc.

              This feature is especially useful if more than one digital
              camera was used to take pictures of an event.  By renaming them
              to a scheme according to date, they will automatically appear in
              order of taking in most directory listings and image browsers.
              Alternatively, if your image browser supports listing by file
              time, you can use the -ft option to set the file time to the
              time the photo was taken.

              Some of the more useful arguments for strftime are:

              %H Hour in 24-hour format (00 - 23)
              %j Day of year as decimal number (001 - 366)
              %m Month as decimal number (01 - 12)
              %M Minute as decimal number (00 - 59)
              %S Second as decimal number (00 - 59)
              %w Weekday as decimal number (0 - 6; Sunday is 0)
              %y Year without century, as decimal number (00 - 99)
              %Y Year with century, as decimal number

              Example:

              jhead -n%Y%m%d-%H%M%S *.jpg This will rename files matched by
              *.jpg in the format YYYYMMDD-HHMMSS

              For a full listing of strftime arguments, look up the strftime
              in them man pages.  Note that some arguments to the strftime
              function (not listed here) produce strings with characters such
              as ':' that may not be valid as part of a filename on some
              systems.


       -nf    Same as '-n' but renames files regardless of original file name.



       -ta<+|-><timediff>
              Adjust time stored in the Exif header by h:mm backwards or
              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 changes all Date/time fields in the exif header,
              including "DateTimeOriginal" (tag 0x9003) and
              "DateTimeDigitized" (tag 0x9004).

       -da<newdate>-<olddate>

              Works like -ta, but for specifying large date offsets, to be
              used when fixing dates from cameras where the date was set
              incorrectly, such as having date and time reset by battery
              removal on some cameras

              Because different months and years have different numbers of
              days in them, a simple offset for months, days, years would lead
              to unexpected results at times.  The time offset is thus
              specified as a difference between two dates, so that jhead can
              figure out exactly how many days the timestamp needs to be
              adjusted by, including leap years and daylight savings time
              changes.  The dates are specified as yyyy:mm:dd.  For sub-day
              adjustments, a time of day can also be included, by specifying
              yyyy:nn:dd/hh:mm or yyyy:mm:dd/hh:mm:ss

              Examples:

              Year on camera was set to 2005 instead of 2004 for pictures
              taken in April
              jhead -da2004:03:01-2005:03:01

              Default camera date is 2002:01:01, and date was reset on
              2005:05:29 at 11:21 am
              jhead -da2005:05:29/11:21-2002:01:01

       -ts    Sets the time stored in the Exif header to what is specified on
              the command line.  Time must be specified as:
              yyyy:mm:dd-hh:mm:ss

       -ds    Sets the date stored in the Exif header to what is specified on
              the command line.  Can be used to set date, just year and month,
              or just year.  Date is specified as: yyyy:mm:dd, yyyy:mm, or
              yyyy


THUMBNAIL MANIPULATION OPTIONS
       -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 the 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.


       -st file
              Save the integral thumbnail to file 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.

              The thumbnail is too low res to really use for very much.

              This feature has an interesting 'relative path' option for
              specifying the thumbnail name.  Whenever the name for file
              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:

              jhead -st thumbnails/&i *.jpg

              would create a thumbnail for each .jpg file in the thumbnails
              directory by the same name, (provided that the thumbnails
              directory exists, of course).  Both Win32 and UNIX shells treat
              the '&'character in a special way, so you have to put quotes
              around that command line option for the

              If a '-' is specified for the output file, the thumbnail is sent
              to stdout. (UNIX build only)


       -rt    Replace thumbnails from the Exif header.  This only works if the
              exif header already contains a thumbnail, and the thumbnail is
              at the end of the header (both always the case if the photo came
              from a digital camera)

       -rgt size
              Regenerate exif thumbnail.  'size' specifies maximum height or
              width of thumbnail.  Relies on 'mogrify' program (from
              ImageMagick) to regenerate the thumbnail.  This only works if
              the image already contains a thumbnail.


ROTATION OPTIONS
       -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 also rotated. 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 rotation field in the Exif header without altering
              the image.  Useful if the images were previously rotated without
              clearing the Exif rotation tag, as some image browsers will auto
              rotate images when the rotation tag is set.  Sometimes,
              thumbnails and rotation  tags can get very out of sync from
              manipulation with various tools.  To reset it all use -norot
              with -rgt to clear this out.


OUTPUT VERBOSITY CONTROL
       -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.

       -q     No output on success, more like Unix programs.

       -V     Print version info and compilation date.  -exifmap Show a map of
              the bytes in the exif header. Useful when analyzing strange exif
              headers, not of much use to non software developers.

       -se    Suppress error messages relating to corrupt Exif header
              structure.

       -c     Concise output.  This causes picture info to be summarized on
              one line instead of several.  Useful for grep-ing through
              images, as well as importing into spread sheets (data is space
              delimited with quotes as text qualifier).


FILE MATCHING OPTIONS
       -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

              jhead -model S100 *.jpg

              I use this option to restrict my JPEG recompensing to those
              images that came from my Canon S100 digicam, (see the -cmd
              option).

       -exonly
              Skip all files that don't have an Exif header.  Photos straight
              from a digital camera have an Exif header, whereas many photo
              manipulation tools discard the Exif header.

       -cmd   Executes the specified command on each JPEG file to be
              processed.

              The Exif section of each file is read before running the
              command, and reinserted 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).

              Example use:

              Having a whole directory of photos from my S100, I run the
              following commands:

              jhead -cmd mogrify -quality 80 &i -model S100 -r *.jpg
              jhead -cmd jpegtran -progressive &i > &o -r *.jpg

              The first command mogrifies all JPEGs in the tree that indicate
              that they are from a Canon S100 in their Exif header to 80%
              quality at the same resolution.  This is a 'lossy' process, so I
              only run it on files that are from the Canon, and only run it
              once.  The next command then takes a JPEGs and converts them to
              progressive JPEGs.  The result is the same images, with no
              discernible differences, stored in half the space.  This
              produces substantial savings on some cameras.


SEE ALSO
       jpegtran(1), mogrify(1), rdjpgcom(1), wrjpgcom(1)

AUTHOR
       Matthias Wandel

BUGS
       After jhead runs a program to rotate or resize an image, the image
       dimensions and thumbnail in the Exif header are not adjusted.

       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 adjust the effective sensor
       resolution when shooting at less than full resolution, causing jhead to
       incorrectly miscalculate the sensor width and 35mm equivalent focal
       length.  The same can result from resizing photos with Photoshop, which
       will manipulate parts of the exif header.  This is often reported as a
       bug in Jhead, but Jhead can't do much about incorrect data.

       Send bug reports to mwandel at sentex dot net.


COPYING PERMISSIONS
       Jhead is 'public domain'.  You may freely copy jhead, and reuse part or
       all of its code in free or proprietary programs.   I do however request
       that you do not post my e-mail address in ways that spam robots can
       harvest it.



jhead 2.90                        05 Feb 2010                         JHEAD(1)
