Image::ExifTool::MIE(3User Contributed Perl DocumentatiImage::ExifTool::MIE(3)NAMEImage::ExifTool::MIE - Read/write MIE meta information
SYNOPSIS
This module is used by Image::ExifTool
DESCRIPTION
This module contains routines required by Image::ExifTool to read and
write information in MIE files.
WHAT IS MIE?
MIE stands for "Meta Information Encapsulation". The MIE format is an
extensible, dedicated meta information format which supports storage of
binary as well as textual meta information. MIE can be used to
encapsulate meta information from many sources and bundle it together
with any type of file.
Features
Below is very subjective score card comparing the features of a number
of common file and meta information formats, and comparing them to MIE.
The following features are rated for each format with a score of 0 to
10:
1) Extensible (can incorporate user-defined information).
2) Meaningful tag ID's (hint to meaning of unknown information).
3) Sequential read/write ability (streamable).
4) Hierarchical information structure.
5) Easy to implement reader/writer/editor.
6) Order of information well defined.
7) Large data lengths supported: >64kB (+5) and >4GB (+5).
8) Localized text strings.
9) Multiple documents in a single file.
10) Compact format doesn't squander disk space or bandwidth.
11) Compressed meta information supported.
12) Relocatable data elements (ie. no fixed offsets).
13) Binary meta information (+7) with variable byte order (+3).
14) Mandatory tags not required (an unecessary complication).
15) Append information to end of file without editing.
Feature number Total
Format 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Score
------ --------------------------------------------- -----
MIE 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 150
PDF 10 10 0 10 0 0 10 0 10 10 10 0 7 10 10 97
PNG 10 10 10 0 8 0 5 10 0 10 10 10 0 10 0 93
XMP 10 10 10 10 2 0 10 10 10 0 0 10 0 10 0 92
AIFF 0 5 10 10 10 0 5 0 0 10 0 10 7 10 0 77
RIFF 0 5 10 10 10 0 5 0 0 10 0 10 7 10 0 77
JPEG 10 0 10 0 10 0 0 0 0 10 0 10 7 10 0 67
EPS 10 10 10 0 0 0 10 0 10 0 0 5 0 10 0 65
CIFF 0 0 0 10 10 0 5 0 0 10 0 10 10 10 0 65
TIFF 0 0 0 10 5 10 5 0 10 10 0 0 10 0 0 60
EXIF 0 0 0 10 5 10 0 0 0 10 0 0 10 0 0 45
IPTC 0 0 10 0 8 0 0 0 0 10 0 10 7 0 0 45
By design, MIE ranks highest by a significant margin. Other formats
with reasonable scores are PDF, PNG and XMP, but each has significant
weak points. What may be surprising is that TIFF, EXIF and IPTC rank
so low.
As well as scoring high in all these features, the MIE format has the
unique ability to encapsulate any other type of file, and provides a
non-invasive method of adding meta information to a file. The meta
information is logically separated from the original file data, which
is extremely important because meta information is routinely lost when
files are edited.
Also, the MIE format supports multiple files by simple concatenation,
enabling all kinds of wonderful features such as linear databases, edit
histories or non-intrusive file updates. This ability can also be
leveraged to allow MIE-format trailers to be added to some other file
types.
MIE 1.1 FORMAT SPECIFICATION (2007-01-21)
File Structure
A MIE file consists of a series of MIE elements. A MIE element may
contain either data or a group of MIE elements, providing a
hierarchical format for storing data. Each MIE element is identified
by a human-readable tag name, and may store data from zero to 2^64-1
bytes in length.
File Signature
The first element in the MIE file must be an uncompressed MIE group
element with a tag name of "0MIE". This restriction allows the first 8
bytes of a MIE file to be used to identify a MIE format file. The
following table lists the two possible initial byte sequences for a
MIE-format file (the first for big-endian, and the second for little-
endian byte ordering):
Byte Number: 0 1 2 3 4 5 6 7
C Characters: ~ \x10 \x04 ? 0 M I E
or ~ \x18 \x04 ? 0 M I E
Hexadecimal: 7e 10 04 ? 30 4d 49 45
or 7e 18 04 ? 30 4d 49 45
Decimal: 126 16 4 ? 48 77 73 69
or 126 24 4 ? 48 77 73 69
Note that byte 1 may have one of the two possible values (0x10 or
0x18), and byte 3 may have any value (0x00 to 0xff).
Element Structure
1 byte SyncByte = 0x7e (decimal 126, character '~')
1 byte FormatCode (see below)
1 byte TagLength (T)
1 byte DataLength (gives D if DataLength < 253)
T bytes TagName (T given by TagLength)
2 bytes DataLength2 [exists only if DataLength == 255 (0xff)]
4 bytes DataLength4 [exists only if DataLength == 254 (0xfe)]
8 bytes DataLength8 [exists only if DataLength == 253 (0xfd)]
D bytes DataBlock (D given by DataLength)
The minimum element length is 4 bytes (for a group terminator). The
maximum DataBlock size is 2^64-1 bytes. TagLength and DataLength are
unsigned integers, and the byte ordering for multi-byte DataLength
fields is specified by the containing MIE group element. The SyncByte
is byte aligned, so no padding is added to align on an N-byte boundary.
FormatCode
The format code is a bitmask that defines the format of the data:
7654 3210
++++ ---- FormatType
---- +--- TypeModifier
---- -+-- Compressed
---- --++ FormatSize
FormatType (bitmask 0xf0):
0x00 - other (or unknown) data
0x10 - MIE group
0x20 - text string
0x30 - list of null-separated text strings
0x40 - integer
0x50 - rational
0x60 - fixed point
0x70 - floating point
0x80 - free space
TypeModifier (bitmask 0x08):
Modifies the meaning of certain FormatTypes (0x00-0x60):
0x08 - other data sensitive to MIE group byte order
0x18 - MIE group with little-endian byte ordering
0x28 - UTF encoded text string
0x38 - UTF encoded text string list
0x48 - signed integer
0x58 - signed rational (denominator is always unsigned)
0x68 - signed fixed-point
Compressed (bitmask 0x04):
If this bit is set, the data block is compressed using Zlib
deflate. An entire MIE group may be compressed, with the exception
of file-level groups.
FormatSize (bitmask 0x03):
Gives the byte size of each data element:
0x00 - 8 bits (1 byte)
0x01 - 16 bits (2 bytes)
0x02 - 32 bits (4 bytes)
0x03 - 64 bits (8 bytes)
The number of bytes in a single value for this format is given by
2**FormatSize (or 1 << FormatSize). The number of values is the
data length divided by this number of bytes. It is an error if the
data length is not an even multiple of the format size in bytes.
The following is a list of all currently defined MIE FormatCode values
for uncompressed data (add 0x04 to each value for compressed data):
0x00 - other data (insensitive to MIE group byte order) (1)
0x01 - other 16-bit data (may be byte swapped)
0x02 - other 32-bit data (may be byte swapped)
0x03 - other 64-bit data (may be byte swapped)
0x08 - other data (sensitive to MIE group byte order) (1)
0x10 - MIE group with big-endian values (1)
0x18 - MIE group with little-endian values (1)
0x20 - ASCII (ISO 8859-1) string (2,3)
0x28 - UTF-8 string (2,3,4)
0x29 - UTF-16 string (2,3,4)
0x2a - UTF-32 string (2,3,4)
0x30 - ASCII (ISO 8859-1) string list (3,5)
0x38 - UTF-8 string list (3,4,5)
0x39 - UTF-16 string list (3,4,5)
0x3a - UTF-32 string list (3,4,5)
0x40 - unsigned 8-bit integer
0x41 - unsigned 16-bit integer
0x42 - unsigned 32-bit integer
0x43 - unsigned 64-bit integer (6)
0x48 - signed 8-bit integer
0x49 - signed 16-bit integer
0x4a - signed 32-bit integer
0x4b - signed 64-bit integer (6)
0x52 - unsigned 32-bit rational (16-bit numerator then denominator) (7)
0x53 - unsigned 64-bit rational (32-bit numerator then denominator) (7)
0x5a - signed 32-bit rational (denominator is unsigned) (7)
0x5b - signed 64-bit rational (denominator is unsigned) (7)
0x61 - unsigned 16-bit fixed-point (high 8 bits is integer part) (8)
0x62 - unsigned 32-bit fixed-point (high 16 bits is integer part) (8)
0x69 - signed 16-bit fixed-point (high 8 bits is signed integer) (8)
0x6a - signed 32-bit fixed-point (high 16 bits is signed integer) (8)
0x72 - 32-bit IEEE float (not recommended for portability reasons)
0x73 - 64-bit IEEE double (not recommended for portability reasons) (6)
0x80 - free space (value data does not contain useful information)
Notes:
1. The byte ordering specified by the MIE group TypeModifier applies
to the MIE group element as well as all elements within the group.
Data for all FormatCodes except 0x08 (other data, sensitive to byte
order) may be transferred between MIE groups with different byte
order by byte swapping the uncompressed data according to the
specified data format. The following list illustrates the byte-
swapping pattern, based on FormatSize, for all format types except
rational (FormatType 0x50).
FormatSize Change in Byte Sequence
-------------------------------------------------
0x00 (8 bits) 0 1 2 3 4 5 6 7 --> 0 1 2 3 4 5 6 7 (no change)
0x01 (16 bits) 0 1 2 3 4 5 6 7 --> 1 0 3 2 5 4 7 6
0x02 (32 bits) 0 1 2 3 4 5 6 7 --> 3 2 1 0 7 6 5 4
0x03 (64 bits) 0 1 2 3 4 5 6 7 --> 7 6 5 4 3 2 1 0
Rational values consist of two integers, so they are swapped as the
next lower FormatSize. For example, a 32-bit rational (FormatSize
0x02, and FormatCode 0x52 or 0x5a) is swapped as two 16-bit values
(ie. as if it had FormatSize 0x01).
2. The TagName of a string element may have an 6-character suffix to
indicate a specific locale. (ie. "Title-en_US", or
"Keywords-de_DE").
3. Text strings are not normally null terminated, however they may be
padded with one or more null characters to the end of the data
block to allow strings to be edited within fixed-length data
blocks. Newlines in the text are indicated by a single LF (0x0a)
character.
4. UTF strings must not begin with a byte order mark (BOM) since the
byte order and byte size are specified by the MIE format. If a BOM
is found, it should be treated as a zero-width non-breaking space.
5. A list of text strings separated by null characters. These lists
must not be null padded or null terminated, since this would be
interpreted as additional zero-length strings. For ASCII and UTF-8
strings, the null character is a single zero (0x00) byte. For
UTF-16 or UTF-32 strings, the null character is 2 or 4 zero bytes
respectively.
6. 64-bit integers and doubles are subject to the specified byte
ordering for both 32-bit words and bytes within these words. For
instance, the high order byte is always the first byte if big-
endian, and the eighth byte if little-endian. This means that some
swapping is always necessary for these values on systems where the
byte order differs from the word order (ie. some ARM systems),
regardless of the endian-ness of the stored values.
7. Rational values are treated as two separate integers. The
numerator always comes first regardless of the byte ordering. In a
signed rational value, only the numerator is signed. The
denominator of all rational values is unsigned (ie. a signed 32-bit
rational of 0x80000000/0x80000000 evaluates to -1, not +1).
8. 32-bit fixed point values are converted to floating point by
treating them as an integer and dividing by an appropriate value.
ie)
16-bit fixed value = 16-bit integer value / 256.0
32-bit fixed value = 32-bit integer value / 65536.0
TagLength
Gives the length of the TagName string. Any value between 0 and 255 is
valid, but the TagLength of 0 is valid only for the MIE group
terminator.
DataLength
DataLength is an unsigned byte that gives the number of bytes in the
data block. A value between 0 and 252 gives the data length directly,
and numbers from 253 to 255 are reserved for extended DataLength codes.
Codes of 255, 254 and 253 indicate that the element contains an
additional 2, 4 or 8 byte unsigned integer representing the data
length.
0-252 - length of data block
255 (0xff) - use DataLength2
254 (0xfe) - use DataLength4
253 (0xfd) - use DataLength8
A DataLength of zero is valid for any element except a compressed MIE
group. A zero DataLength for an uncompressed MIE group indicates that
the group length is unknown. For other elements, a zero length
indicates there is no associated data. A terminator element must have
a DataLength of 0, 6 or 10, and may not use an extended DataLength.
TagName
The TagName string is 0 to 255 bytes long, and is composed of the ASCII
characters A-Z, a-z, 0-9 and underline ('_'). Also, a dash ('-') is
used to separate the language/country code in the TagName of a
localized text string, and a units string (possibly containing other
ASCII characters) may be appear in brackets at the end of the TagName.
The TagName string is NOT null terminated. A MIE element with a tag
string of zero length is reserved for the group terminator.
MIE elements are sorted alphabetically by TagName within each group.
Multiple elements with the same TagName are allowed, even within the
same group.
TagNames should be meaningful. Case is significant. Words should be
lowercase with an uppercase first character, and acronyms should be all
upper case. The underline ("_") is provided to allow separation of two
acronyms or two numbers, but it shouldn't be used unless necessary. No
separation is necessary between an acronym and a word (ie.
"ISOSetting").
All TagNames should start with an uppercase letter. An exception to
this rule allows tags to begin with a digit (0-9) if they must come
before other tags in the sort order, or a lowercase letter (a-z) if
they must come after. For instance, the '0Type' element begins with a
digit so it comes before, and the 'data' element begins with a
lowercase letter so that it comes after meta information tags in the
main "0MIE" group.
Tag names for localized text strings have an 6-character suffix with
the following format: The first character is a dash ('-'), followed by
a 2-character lower case ISO 639-1 language code, then an underline
('_'), and ending with a 2-character upper case ISO 3166-1 alpha 2
country code. (ie. "-en_US", "-en_GB", "-de_DE" or "-fr_FR". Note
that "GB", and not "UK" is the code for Great Britain, although "UK"
should be recognized for compatibility reasons.) The suffix is
included when sorting the tags alphabetically, so the default locale
(with no tag-name suffix) always comes first. If the country is
unknown or not applicable, a country code of "XX" should be used.
Tags with numerical values may allow units of measurement to be
specified. The units string is stored in brackets at the end of the
tag name, and is composed of zero or more ASCII characters in the range
0x21 to 0x7d, excluding the bracket characters 0x28 and 0x29. (ie.
"Resolution(/cm)" or "SpecificHeat(J/kg.K)".) See
Image::ExifTool::MIEUnits for details. Unit strings are not localized,
and may not be used in combination with localized text strings.
Sets of tags which would require a common prefix should be added in a
separate MIE group instead of adding the prefix to all tag names. For
example, instead of these TagName's:
ExternalFlashType
ExternalFlashSerialNumber
ExternalFlashFired
one would instead designate a separate "ExternalFlash" MIE group to
contain the following elements:
Type
SerialNumber
Fired
DataLength2/4/8
These extended DataLength fields exist only if DataLength is 255, 254
or 253, and are respectively 2, 4 or 8 byte unsigned integers giving
the data block length. One of these values must be used if the data
block is larger than 252 bytes, but they may be used if desired for
smaller blocks too (although this may add a few unnecessary bytes to
the MIE element).
DataBlock
The data value for the MIE element. The format of the data is given by
the FormatCode. For MIE group elements, the data includes all
contained elements and the group terminator.
MIE groups
All MIE data elements must be contained within a group. A group begins
with a MIE group element, and ends with a group terminator. Groups may
be nested in a hierarchy to arbitrary depth.
A MIE group element is identified by a format code of 0x10 (big endian
byte ordering) or 0x18 (little endian). The group terminator is
distinguished by a zero TagLength (it is the only element allowed to
have a zero TagLength), and has a FormatCode of 0x00.
The MIE group element is permitted to have a zero DataLength only if
the data is uncompressed. This special value indicates that the group
length is unknown (otherwise the minimum value for DataLength is 4,
corresponding the the minimum group size which includes a terminator of
at least 4 bytes). If DataLength is zero, all elements in the group
must be parsed until the group terminator is found. If non-zero,
DataLength includes the length of all elements contained within the
group, including the group terminator. Use of a non-zero DataLength is
encouraged because it allows readers quickly skip over entire MIE
groups. For compressed groups DataLength must be non-zero, and is the
length of the compressed group data (which includes the compressed
group terminator).
Group Terminator
The group terminator has a FormatCode and TagLength of zero. The
terminator DataLength must be 0, 6 or 10 bytes, and extended DataLength
codes may not be used. With a zero DataLength, the byte sequence for a
terminator is "7e 00 00 00" (hex). With a DataLength of 6 or 10 bytes,
the terminator data block contains information about the length and
byte ordering of the preceding group. This additional information is
recommended for file-level groups, and is used in multi-document MIE
files and MIE trailers to allow the file to be scanned backwards from
the end. (This may also allow some documents to be recovered if part
of the file is corrupted.) The structure of this optional terminator
data block is as follows:
4 or 8 bytes GroupLength (unsigned integer)
1 byte ByteOrder (0x10 or 0x18, same as MIE group)
1 byte GroupLengthSize (0x04 or 0x08)
The ByteOrder and GroupLengthSize values give the byte ordering and
size of the GroupLength integer. The GroupLength value is the total
length of the entire MIE group ending with this terminator, including
the opening MIE group element and the terminator itself.
File-level MIE groups
File-level MIE groups may NOT be compressed.
All elements in a MIE file are contained within a special group with a
TagName of "0MIE". The purpose of the "OMIE" group is to provide a
unique signature at the start of the file, and to encapsulate
information allowing files to be easily combined. The "0MIE" group
must be terminated like any other group, but it is recommended that the
terminator of a file-level group include the optional data block
(defined above) to provide information about the group length and byte
order.
It is valid to have more than one "0MIE" group at the file level,
allowing multiple documents in a single MIE file. Furthermore, the MIE
structure enables multi-document files to be generated by simply
concatenating two or more MIE files.
Scanning Backwards through a MIE File
The steps below give an algorithm to quickly locate the last document
in a MIE file:
1. Read the last 10 bytes of the file. (Note that a valid MIE file
may be as short as 12 bytes long, but a file this length contains
only an an empty MIE group.)
2. If the last byte of the file is zero, then it is not possible to
scan backward through the file, so the file must be scanned from
the beginning. Otherwise, proceed to the next step.
3. If the last byte is 4 or 8, the terminator contains information
about the byte ordering and length of the group. Otherwise, stop
here because this isn't a valid MIE file.
4. The next-to-last byte must be either 0x10 indicating big-endian
byte ordering or 0x18 for little-endian ordering, otherwise this
isn't a valid MIE file.
5. The value of the preceding 4 or 8 bytes gives the length of the
complete file-level MIE group (GroupLength). This length includes
both the leading MIE group element and the terminator element
itself. The value is an unsigned integer with a byte length given
in step 3), and a byte order from step 4). From the current file
position (at the end of the data read in step 1), seek backward by
this number of bytes to find the start of the MIE group element for
this document.
This algorithm may be repeated again beginning at this point in the
file to locate the next-to-last document, etc.
The table below lists all 5 valid patterns for the last 14 bytes of a
file-level MIE group, with all numbers in hex. The comments indicate
the length and byte ordering of GroupLength (xx) if available:
?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 7e 00 00 00 - (no GroupLength)
?? ?? ?? ?? 7e 00 00 06 xx xx xx xx 10 04 - 4 bytes, big endian
?? ?? ?? ?? 7e 00 00 06 xx xx xx xx 18 04 - 4 bytes, little endian
7e 00 00 0a xx xx xx xx xx xx xx xx 10 08 - 8 bytes, big endian
7e 00 00 0a xx xx xx xx xx xx xx xx 18 08 - 8 bytes, little endian
Trailer Signature
The MIE format may be used for trailer information appended to other
types of files. When this is done, a signature must appear at the end
of the main MIE group to uniquely identify the MIE format trailer. To
achieve this, a "zmie" trailer signature is written as the last element
in the main "0MIE" group. This element has a FormatCode of 0, a
TagLength of 4, a DataLength of 0, and a TagName of "zmie". With this
signature, the hex byte sequence "7e 00 04 00 7a 6d 69 65" appears
immediately before the final group terminator, and the last 22 bytes of
the trailer correspond to one of the following 4 patterns (where the
trailer length is given by "xx", as above):
?? ?? ?? ?? 7e 00 04 00 7a 6d 69 65 7e 00 00 06 xx xx xx xx 10 04
?? ?? ?? ?? 7e 00 04 00 7a 6d 69 65 7e 00 00 06 xx xx xx xx 18 04
7e 00 04 00 7a 6d 69 65 7e 00 00 0a xx xx xx xx xx xx xx xx 10 08
7e 00 04 00 7a 6d 69 65 7e 00 00 0a xx xx xx xx xx xx xx xx 18 08
Note that the zero-DataLength terminator may not be used here because
the trailer length must be known for seeking backwards from the end of
the file.
Multiple trailers may be appended to the same file using this
technique.
MIE Data Values
MIE data values for a given tag are usually not restricted to a
specific FormatCode. Any value may be represented in any appropriate
format, including numbers represented in string (ASCII or UTF) form.
It is preferred that closely related values with the same format are
written to a single tag instead of using multiple tags. This improves
localization of like values and decreases MIE element overhead. For
instance, instead of separate ImageWidth and ImageHeight tags, a single
ImageSize tag is defined.
Tags which may take on a discrete set of values should have meaningful
values if possible. This improves the extensibility of the format and
allows a more reasonable interpretation of unrecognized values.
Numerical Representation
Integer and floating point numbers may be represented in binary or
string form. In string form, integers are a series of digits with an
optional leading sign (ie. "[+|-]DDDDDD"), and multiple values are
separated by a single space character (ie. "23 128 -32"). Floating
point numbers are similar but may also contain a decimal point and/or a
signed exponent with a leading 'e' character (ie.
"[+|-]DD[.DDDDDD][e(+|-)EEE]"). The string "inf" is used to represent
infinity. One advantage of numerical strings is that they can have an
arbitrarily high precision because the possible number of significant
digits is virtually unlimited.
Note that numerical values may have associated units of measurement
which are specified in the "TagName" string.
Date/Time Format
All MIE dates are strings in the form "YYYY:mm:dd HH:MM:SS.ss+HH:MM".
The fractional seconds (".ss") are optional, and if included may
contain any number of significant digits (unlike all other fields which
are a fixed number of digits and must be padded with leading zeros if
necessary). The timezone ("+HH:MM" or "-HH:MM") is recommended but not
required. If not given, the local system timezone is assumed.
MIME Type
The basic MIME type for a MIE file is "application/x-mie", however the
specific MIME type depends on the type of subfile, and is obtained by
adding "x-mie-" to the MIME type of the subfile. For example, with a
subfile of type "image/jpeg", the MIE file MIME type is
"image/x-mie-jpeg". But note that the "x-" is not duplicated if the
subfile MIME type already starts with "x-". So a subfile with MIME
type "image/x-raw" is contained within a MIE file of type
"image/x-mie-raw", not "image/x-mie-x-raw". In the case of multiple
documents in a MIE file, the MIME type is taken from the first
document. Regardless of the subfile type, all MIE-format files should
have a filename extension of ".MIE".
Levels of Support
Basic MIE reader/writer applications may choose not to provide support
for some advanced features of the MIE format. Features which may not
be supported by all software are:
Compression
Software not supporting compression must ignore compressed elements
and groups, but should be able to process the remaining
information.
Large data lengths
Some software may limit the maximum size of a MIE group or element.
Historically, a limit of 2GB may be imposed by some systems.
However, 8-byte data lengths should be supported by all
applications provided the value doesn't exceed the system limit.
(ie. For systems with a 2GB limit, 8-byte data lengths should be
supported if the upper 17 bits are all zero.) If a data length
above the system limit is encountered, it may be necessary for the
application to stop processing if it can not seek to the next
element in the file.
EXAMPLES
This section gives examples for working with MIE information using
ExifTool.
Encapsulating Information with Data in a MIE File
The following command encapsulates any file recognized by ExifTool
inside a MIE file, and initializes MIE tags from information within the
file:
exiftool -o new.mie -tagsfromfile FILE '-mie:all<all' \
'-subfilename<filename' '-subfiletype<filetype' \
'-subfilemimetype<mimetype' '-subfiledata<=FILE'
where "FILE" is the name of the file.
For unrecognized files, this command may be used:
exiftool -o new.mie -subfilename=FILE -subfiletype=TYPE \
-subfilemimetype=MIME '-subfiledata<=FILE'
where "TYPE" and "MIME" represent the source file type and MIME type
respectively.
Adding a MIE Trailer to a File
The MIE format may also be used to store information in a trailer
appended to another type of file. Beware that trailers may not be
compatible with all file formats, but JPEG and TIFF are two formats
where additional trailer information doesn't create any problems for
normal parsing of the file. Also note that this technique has the
disadvantage that trailer information is commonly lost if the file is
subsequently edited by other software.
Creating a MIE trailer with ExifTool is a two-step process since
ExifTool can't currently be used to add a MIE trailer directly. The
example below illustrates the steps for adding a MIE trailer with a
small preview image ("small.jpg") to a destination JPEG image
("dst.jpg").
Step 1) Create a MIE file with a TrailerSignature containing the
desired information:
exiftool -o new.mie -trailersignature=1 -tagsfromfile small.jpg \
'-previewimagetype<filetype' '-previewimagesize<imagesize' \
'-previewimagename<filename' '-previewimage<=small.jpg'
Step 2) Append the MIE information to another file. In Unix, this can
be done with the 'cat' command:
cat new.mie >> dst.jpg
Once added, ExifTool may be used to edit or delete a MIE trailer in a
JPEG or TIFF image.
Multiple MIE Documents in a Single File
The MIE specification allows multiple MIE documents (or trailers) to
exist in a single file. A file like this may be created by simply
concatenating MIE documents. ExifTool may be used to access
information in a specific document by adding a copy number to the MIE
group name. For example:
# write the Author tag in the second MIE document
exiftool -mie2:author=phil test.mie
# delete the first MIE document from a file
exiftool -mie1:all= test.mie
Units of Measurement
Some MIE tags allow values to be specified in different units of
measurement. In the MIE file format these units are combined with the
tag name, but when using ExifTool they are specified in brackets after
the value:
exiftool -mie:gpsaltitude='7500(ft)' test.mie
If no units are provided, the default units are written.
Localized Text
Localized text values are accessed by adding a language/country code to
the tag name. For example:
exiftool -comment-en_us='this is a comment' test.mie
REVISIONS
2007-01-21 - Specified LF character (0x0a) for text newline sequence
2007-01-19 - Specified ISO 8859-1 character set for extended ASCII codes
2007-01-01 - Improved wording of Step 5 for scanning backwards in MIE file
2006-12-30 - Added EXAMPLES section and note about UTF BOM
2006-12-20 - MIE 1.1: Changed meaning of TypeModifier bit (0x08) for
unknown data (FormatType 0x00), and documented byte swapping
2006-12-14 - MIE 1.0: Added Data Values and Numerical Representations
sections, and added ability to specify units in tag names
2006-11-09 - Added Levels of Support section
2006-11-03 - Added Trailer Signature
2005-11-18 - Original specification created
AUTHOR
Copyright 2003-2010, Phil Harvey (phil at owl.phy.queensu.ca)
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself. The MIE format itself is also
copyright Phil Harvey, and is covered by the same free-use license.
REFERENCES
<http://owl.phy.queensu.ca/~phil/exiftool/MIE1.1-20070121.pdf>
SEE ALSO
"MIE Tags" in Image::ExifTool::TagNames, Image::ExifTool::MIEUnits,
Image::ExifTool(3pm)perl v5.10.1 2010-01-25 Image::ExifTool::MIE(3)
