NAME
exifprobe - probe and report structure and metadata content of camera
image files
SYNOPSIS
exifprobe [options] filename(s)
DESCRIPTION
Exifprobe reads image files produced by digital cameras (including
several so-called "raw" file formats) and reports the structure of the
files and the auxilliary data and metadata contained within them. In
addition to TIFF, JPEG, and EXIF, the program understands several
formats which may contain "raw" camera data, including MRW, CIFF/CRW,
JP2/JPEG2000, RAF, and X3F, as well as most most TIFF-derived "raw"
formats, including DNG, ORF, CR2, NEF, K25/KDC/DCR, and PEF. Other TIFF
or JPEG-derived formats (which begin with a TIFF header or JPEG marker)
should also be readable. The program attempts to display ALL
information in the image file, in a manner which mimics the structure
of the file as closely as possible.
Where possible, output is not limited to “known” data items. I.e. for
tagged file formats, unknown tags will be identified by tag number and
type, and values shown without interpretation. Proprietary, untagged or
fixed format files do not permit this, but unknown or undefined data
can usually be dumped in a hex/ascii format for examination, so long as
the file structure is understood. The program will report the contents
of any properly structured TIFF IFD or CIFF directory encountered, even
when entry tags are not recognized. Recognized TIFF, TIFF/EP, DNG, and
CIFF tags are expanded, including EXIF2.2 sections and camera
MakerNotes which are found to be in TIFF IFD format. TIFF and/or JPEG
sections found in MRW, RAF or JP2 files will be reported, along with
the “native” sections of those formats. JP2 boxes will be reported
whether known or unknown, and expanded if known. Unknown boxes cannot
be expanded, since JP2 is not tagged below the box (or sub-box) level.
An effort is made to identify all sub-images (in any image format)
contained in multi-image files; the location, size, and format of such
images is reported, and a hex/ascii dump of the image data may be
requested. Image data is not processed, but the program will recognize
and report all standard JPEG and JPEG2000 markers (including JPEG APPn
markers) and will expand APP0 (JFIF/JFXX) and APP1 (EXIF) sections.
Since the program does not attempt to display images or modify the
contents of files, it can often recover from and report failures or
warn about structural oddities which would confuse a display or image
edit program.
There are a wide variety of output formats, selectable in detail by the
“lower case” options described in the OPTIONS section below. These
options select which items to print, and within narrow confines, how
and where to print them. A large number of combinations of options
exist, and some of those combinations may not be sensible. In order to
avoid the need for constant creativity or invention, three
“prefabricated” output formats are provided, selected by the upper case
option letters.
The structural (-S) output format (default) provides a description of
the image file which mimics as closely as possible the layout and
structure of the data in the image file, including file offsets of
headers, section and segment markers, fully described TIFF IFDs, CIFF
directories, or JP2 boxes, and the location of actual image and/or
thumbnail data. The contents of each section are indented relative to
the beginning of the section, and ”offset” values for TIFF IFDs and
CIFF directories are reported at the offsets where they are found
(usually following the entry list for TIFF, or in the HEAP for CIFF).
The peculiar “reverse” structures of CIFF and X3F formats are handled
sensibly.
The report format (-R) shows the “logical” structure of the image file,
but eliminates addresses, offsets, IFD value types and counts, etc.,
and prints “offset” directory values inline, while otherwise preserving
the primary structure of the data.
The list format (-L) omits all structural data. It writes only “tag”
values from TIFF, Exif, and MakerNote IFDs, CIFF or other format
directories or JP2 boxes, including section and image offsets and
sizes. Identifiable values from non-tagged formats are written in a
similar manner. This format may be useful for extracting information
for photo galleries.
The structural format is default. This format provides maximum
information about the contents of an image file, and may reveal
information (sometimes important) which other formats (or image info
programs) may hide.
In all formats, the filename, file type, file size, an image summary,
and a summary file format will be displayed (even when all other output
is disabled by option). The image summary includes a summary report,
for each subimage found, giving the image type, compression type (if
any), pixel size, data length, file offset where found, and section of
the file which includes or references the image. In some cases, short
remarks may be included for images mentioned but not found, etc. The
summary concludes with the number of images found, and number of images
not found (if any). The summary is followed by a listing of format
sections found (TIFF/JPEG/EXIF, etc.) and a type identifier for TIFF-
derived types (e.g. CR2) where possible.
An environment variable may be set to a list of options to customize
the default output behavior (see below).
MakerNotes
Camera-generated images which contain EXIF sections may also contain
sections introduced by a MakerNote tag, which may contain information
about camera or firmware settings used to produce the image. The
structure and contents of MakerNote sections is not mandated by the
Exif specification, but many camera MakerNotes are written in TIFF IFD
format, possibly offset following an ID string or new TIFF header (or
both), and sometimes with inventive handling of “offsets”. Exifprobe
currently understands and automatically detects such schemes and prints
the contents of the IFD (and the ID string, if present). This
detection is not dependent upon make or model of camera. Make and
Model information will usually be available from the first TIFF IFD in
the file; this information may be used to interpret the MakerNote
information for “known” cameras; otherwise, tag numbers, sizes, types,
and raw values from the IFD will be shown (if permitted by option
settings).
Some camera makes are known to use more than one version of MakerNote,
depending upon model. If an unknown model from that maker is
encountered, the note will be briefly examined and a noteversion
assigned automatically if possible. If that fails, the note will be
displayed without interpretation.
MakerNotes which are not in a recognizable IFD format will be reported
(start and end offsets) in structural (-S) and report (-R) formats ,
and the beginning of the note section hex/ascii dumped. The remainder
of the note may be dumped, in whole or in part, by the -M option (see
below).
In list (-L) format, the starting file offset and length supplied by
the MakerNote tag will be reported, and three “pseudo” tags which
report the offset (MakerNote.Offset), size (MakerNote.Length) and
scheme (MakerNote.Scheme) will appear.
JPEG APPn
In JPEG interchange format files, APP0 (JFIF,JFXX) and APP1 (Exif)
segments will be fully decoded, and the “printable” portions of APP12
sections will be displayed. APP3 (Meta) sections will be expanded and
the contained TIFF IFD will be displayed, although little
interpretation is done. Other APP markers will be reported, and the
sections may be hex/ascii dumped in whole or in part using the -A
option. APP1 sections not marked as Exif will be treated as unknown.
ANSI Color
The program (by default) emits ANSI color escape sequences to highlight
Exif, MakerNote , and Interoperability sub-sections. Errors and
warnings are highlighted in red. These sequences are effective, of
course, only for terminals or terminal emulators (e.g. xterm) which
respond to ANSI color escape sequences. If a pager is used to display
the output when these sequences are present, a “raw” option to the
pager may be required (e.g. less -R). The use of these sequences may
be toggled by the -c option. LIST mode turns color sequences off.
The program may be compiled without support for color sequences.
OUTPUT FORMATS
In all formats, and regardless of option setting, the first three lines
of output for each file processed are the filename, image type (TIFF,
CIFF, JP2, etc.), and the file size. If the type (taken from the file
header) specifies a data byte order, the byte order will be indicated
with the type as ‘II’ (Intel byte order) or ‘MM’ (Motorola byte order).
The image summary and summary format will always be printed at the end.
Structural Format
Structural format output begins with a display of the file header. The
header is followed by lines of the form
<IFD0>
...
</IFD0>
<APP0>
...
</APP0>
<DIRECTORY>
...
</DIRECTORY>
etc. to indicate the beginning and end of each “section” of the file.
Actual section names will, of course, depend upon the file format
and/or the tags encountered. Only the TIFF IFD format is described
here; other formats are similar, except that JP2 box names are printed
inside square (rather than angle) brackets, and MRW section names
inside curly braces.
Within sections, directory entries, subdirectories, the contents of
known APP sections, JPEG segment markers, etc. are printed. Non-jpeg
image data sections will be shown with a few lines of hex/ascii dump of
the beginning of the data.
Each line of output is preceded by a file offset given in hex and
decimal. File offsets are preceded by the character ‘@’, except that
section end markers are preceded by ‘-’ and the character ‘>’ may be
used to mark sections which are located outside the IFD in which they
are declared. If that section includes a subsection which is similarly
afflicted, the ’>’ is replaced by ’+’ in the subsection. In JP2 files,
the ’@’ is replaced by ’=’, for no particular reason.
JPEG and JPEG2000 segment markers are written with the marker name, and
the decoded values of any information associated with the marker.
TIFF information is written in a manner which reflects the structure of
the IFD, with all values interpreted according to the applicable
specification where possible. All IFD fields are reported. The
following fields will appear on each line (in the order given,
following the file offset):
· Tag number in hex and decimal representations, enclosed in
brackets.
· Tag name (where known); names for unknown tags are created as a
hex representation of the tag number prefixed by the string
’TAG_’.
· The TIFF type number, name, and byte count for the associated
value, enclosed in square brackets.
· The “value/offset” for the entry. If the value fits in the four
bytes of the entry, the value is printed directly.
If the value for the entry did not fit in the four bytes of the
entry, then the value found is an offset to the actual location
of the data; that offset is printed preceded by an ’@’ symbol.
The actual value will be printed later, at the file offset where
it was found (except in some non-conforming MakerNote IFDs). If
the value requires interpretation (e.g. TIFF Orientation) it is
followed by an ’=’ sign and the interpretation, enclosed in
double quotes (e.g. 0,0 top left).
The list of entries will be followed by a line giving the offset to the
next IFD (often 0) which is always found at the end of a TIFF IFD entry
list.
If there were offset entries found in the list above, the TIFF (and
Exif) specification requires that they will be located next in the
file, immediately following the dirctory entries. This stricture is
frequently ignored in MakerNotes and TIFF-derived formats. A line
reporting the beginning of these offset values will be printed
immediately after the next IFD offset, followed by one line for each
offset entry, with the tag name repeated, followed by the actual value,
followed by its interpretation (if any).
Multiple values in entries are printed on a single line, but large
lists will be elided, with just the first two or three values shown,
followed by an ellipsis, followed by the last value, the number of
values, and the offset of the last value in the list. The full value
list may be printed using the -eA option.
In structural format, ascii strings in the entry are printed for the
entire length given in the IFD entry, including nulls and non-ascii
values (if present), which are printed in ‘backslashed’ octal notation.
The -ea option may be used to force ascii values to be printed only up
to the first null. This option is often necessary for CIFF format
files, and is enabled by default in “list” mode.
Entries are indented slightly from the start identifier for the IFD,
and subsegments (e.g. an Exif IFD, SubIFD, or MakerNote) will be
further indented in order to indicate the structure of the file.
The resulting output displays the contents of the IFD much as it
appears in the file (see the TIFF or EXIF specifications for
descriptions of the IFD format).
Finally, the start and end of actual image data for the primary image
(and possibly thumbnail or reduced-resolution image) is reported at the
end. For JPEG images, this usually includes display of the JPEG
segment markers within the image. Binary format image data will be
shown with a brief hex/ascii dump of the beginning of the data, between
start and end markers.
Note that values preceded by ‘@’ are always offsets from the beginning
of the file to the actual value. IFD offsets are usually recorded in
the file as offsets relative to the beginning of the TIFF header (which
is offset from the beginning of the file in JPEG APP1 files) but are
adjusted by exifprobe to show offset from the beginning of the file.
If it is important to see the recorded value, the -er option may be
used to print the recorded value in parentheses, following the adjusted
file offset.
Report Format
The report format (-R) displays all sections and segments of the image
file, including start and end of sections, but eliminates much of the
“cruft” of the structural format by eliminating address/offset
information and much of the ‘internal’ information from the TIFF IFD
(tag number, type and count). Offset values are printed inline with
the tag name. The output is indented to show the logical structure of
the image file, but is much less difficult to view than the structural
format.
List format
The list format (-L) suppresses structural information, writing only
content in the format tagname = value or tagname = value = what value
means. For non-tagged file formats, the tagname will be replaced by a
fixed identifier for the item. In LIST format, “long” tagnames are
used, which include the names of all parent sections of the section in
which the data is found. Long tagnames can be toggled off, although
this is unwise if the file contains multiple image sections.
The “value” of tags or items which represent an offset to a subsection
or image are printed in list format as “@offset:length”.
The List format is used by the auxilliary script exifgrep, which
permits selective extraction of information e.g. for photo galleries,
and output in (almost) “shell variable” format.
Custom Formats
The -Z option “zeroes” all option flags (except the longnames
modifier), after which the lower-case options may be used to set
desired options. The lower-case options are ‘toggles’, which may also
be used to turn off items in the pre-defined formats.
As an example, the command:
exifprobe -Z -et somefile.tif
may be used to list just the TIFF and Exif tags, without values (or
anything else) in “long name” format.
exifprobe -eNnT somefile.tif
will print in structural format, suppressing output of hex and decimal
tag numbers, and tag type and count.
The “zero-level” output still reports the file data and image summary
as described above.
OPTIONS
The environment variable EXIFPROBE_OPTIONS may be set to any valid
option string, which will be evaluated before command line options.
E.g.
export EXIFPROBE_OPTIONS=’-L -c’
will make list format the default output format, and re-enable the
color sequences turned off by -L.
Options are evaluated from left to right, so -Z should be given first,
while -D (decimal only) or -X (hex only) should be given last.
-S Structure mode: (default) almost everything; offset values
not inline
-R Report mode: like structural, but only tagnames and decimal
values, indented, inline
-L List mode: print only tags and values (including interpreted
values); no section info; no color
-Z turn off (zero) all optional output. Prints only filename,
filetype, filesize, image summary, and file format.
-c toggle use of ANSI color control sequences to emphasize EXIF
sections. (default ’on’ except list mode, unless compiled
with no color support)
-a toggle printing of addresses (file offsets) in hex and
decimal
-I three-way toggle indent (after address -> before -> none)
-o toggle “inline” print of offset IFD values
-p[items] toggle print identifiers for:
s - sections (IFDs, APPn)
g - segments (JPEG segments)
a - JPEG APP0...APPn entries
l - long names (dot-separated list of parent sections
preceding item name)
e - entries. Includes tag names, numbers, types, values.
m - print MakerNote scheme description
M - watch debug of MakerNote scheme detection
-e[items] toggle print IFD entry items:
t - tagname
n - tag number in decimal
N - tag number in hex
T - entry type and count
v - value in decimal
V - value in hex
o - file offset to value in decimal
O - file offset to value in hex
r - relative (unadjusted) offset in decimal
R - also print “raw” values where normal values are
computed (e.g. rational values, or some MakerNote values
where APEX values must be computed from a raw value).
A - print ALL elements of multiple-value tags
a - ascii "ignore length" (stop at first null)
-D limit all enabled numerical values to decimal only
(addresses, tag numbers, offsets, values)
-X limit all enabled numerical values to hex only (addresses,
tag numbers, offsets, values)
-U[len|a] dump len (or all) bytes of UNDEFINED data found in TIFF IFDS
in hex/ascii form (but only if the structure of the data is
not known)
-M[len|a] dump len (or all) bytes of unrecognized MakerNotes in
hex/ascii form (but only if the structure of the data is not
known)
-A[len|a] dump len (or all) bytes of unrecognized JPEG APP segments in
hex/ascii form (but only if the structure of the data is not
known)
-B[len|a] dump len (or all) bytes of binary image data or failed JPEG
image data
-C[make]+[model]
print a list of camera makes/models matching make or model as
substrings. ‘+’ by itself prints everything
-O start_offset
start processing at file offset start_offset
-n print filename at beginning of each line of output (useful
when grepping multiple files in LIST mode)
-N noteversion
force use of note version noteversion when interpreting
MakerNotes. Useful only if you know what you’re doing.
-m make Force the makernote code to interpret the note according to
the make given, rather than that contained in the file.
-l model force the makernote code to interpret the note according to
the model given, rather than that contained in the file.
-t This option has effect only if set in EXIFPROBE_OPTIONS. If
set when command line options are processed, color will be
be off by default if the output is not to a tty. Any command
line option which toggles or sets color (e.g. “-R”) will turn
color back on.
-u Print “raw” Unicode data. Normally 16 bit data is printed as
though the high byte is zero (which is often the case).
Writing the nulls would annoy most ascii terminal devices, so
the default is more hospitable. The -u option forces
printing of the full value.
-h print a help message
-V print program version and copyright
SEE ALSO
exifgrep(1)
The TIFF6 specification:
https://partners.adobe.com/asn/developer/PDFS/TN/TIFF6.pdf
The Exif 2.2 specification:
http://tsc.jeita.or.jp/avs/data/cp3451.pdf
The JFIF specification:
http://www.w3.org/Graphics/JPEG/jfif3.pdf
The TIFF/EP specification:
http://www.map.tu.chiba-u.ac.jp/IEC/100/TA2/recdoc/N4378.pdf
The CIFF specification
http://xyrion.org/ciff/CIFFspecV1R04.pdf
The X3F public specification
http://www.sd9.org.uk/X3F_Format.pdf
The JPEG2000 public draft (outdated)
http://www.jpeg.org/public/fcd15444-1.pdf
DIAGNOSTICS
Most diagnostics are printed “inline” to stdout, in red if color is
enabled, and the program attempts to proceed.
BUGS
Interpretation of MakerNote data for specific cameras is incomplete and
probably always will be. The X3F specification is incomplete, and the
final JPEG2000/JP2 specification is not freely available; support for
these formats is therefore not complete, and may not be entirely
accurate.
The RAF file format support is preliminary (there is no published
specification).
Floating point values read from the file are expected to be in IEEE
format (or at least, native format); i.e. no conversions are attempted.
ANSI color sequence support should use termcap/terminfo facilities; it
does not.
AUTHOR
Duane H. Hesser
dhh@virtual-cafe.com
LOCAL
