JHEAD(1)JHEAD(1)NAMEjhead - Digicam JPEG Exif header manipulation tool
SYNOPSISjhead [ options ] [ file... ]
DESCRIPTIONjhead 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 for‐
mat.
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 spec‐
ifying 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 origi‐
nals directory by the same name, Both Win32 and most Unix shells
treat the '&' character in a special way, so you have to put
quotes around that command line option for the '&' to even be
passed to the program.
-dc Delete comment field from the JPEG header. Note that the com‐
ment 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 sec‐
tions intact.
-dx Delete the XMP section, if present. Leaves other metadata sec‐
tions intact.
-du Delete sections of jpeg that are not Exif, not comment, and oth‐
erwise 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 lim‐
ited 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
-n option to force renaming of all files. If the new name con‐
tains 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 strf‐
time 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 cre‐
ated.
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 cam‐
era 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 YYYYM‐
MDD-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 sys‐
tems.
-ta<+|-><timediff>
Adjust time stored in the Exif header by h:mm forwards or back‐
wards. 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.
Examples:
Add 1 hourand 5 minutes to the time
jhead -ta+1:05
Decrease time by one second:
jhead -ta-0:0:1
This option changes all Date/time fields in the exif header,
including "DateTimeOriginal" (tag 0x9003) and "DateTimeDigi‐
tized" (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 speci‐
fied 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 interest‐
ing 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 spec‐
ifying the thumbnail name. Whenever the name for file contains
the characters '&i', jhead will substitute the original file‐
name 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 direc‐
tory 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 '&' to even be passed to the
program.
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 ImageMag‐
ick) 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 distribu‐
tions. For windows, you need to get a copy of it. After rota‐
tion, the orientation tag of the Exif header is set to '1' (nor‐
mal 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 use‐
ful with newer Canon cameras, that set the orientation tag auto‐
matically 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, thumb‐
nails and rotation tags can get very out of sync from manipula‐
tion 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 sec‐
onds, 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 struc‐
ture.
-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 fol‐
lowing command will list only images that are from an S100 cam‐
era:
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 pro‐
cessed.
The Exif section of each file is read before running the com‐
mand, 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 fol‐
lowing commands:
jhead-cmd "mogrify -quality 80 &i" -model S100 *.jpg
jhead-cmd "jpegtran -progressive &i > &o" *.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 dis‐
cernible differences, stored in half the space. This produces
substantial savings on some cameras.
SEE ALSOjpegtran(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 res‐
olution 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 3.00 2 Feb 2015 JHEAD(1)
