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NAMEImage::ExifTool::MIE - Read/write MIE meta information
SYNOPSISThis module is used by Image::ExifTool
DESCRIPTIONThis module contains routines required by Image::ExifTool to read and write information in
WHAT IS MIE?
FeaturesBelow is very subjective score card comparing the features of a number of common file and meta information formats, and comparing them to
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 unnecessary 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
As well as scoring high in all these features, the
MIE 1.1 FORMAT SPECIFICATION (2007-01-21)
File SignatureThe first element in the
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).
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
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 MIEgroup 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
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)
The byte ordering specified by the MIEgroup TypeModifier applies to theMIEgroup element as well as all elements within the group. Data for all FormatCodes except 0x08 (other data, sensitive to byte order) may be transferred betweenMIEgroups 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).
- The TagName of a string element may have an 6-character suffix to indicate a specific locale. (eg. ``Title-en_US'', or ``Keywords-de_DE'').
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.
UTFstrings must not begin with a byte order mark (BOM) since the byte order and byte size are specified by theMIEformat. If aBOMis found, it should be treated as a zero-width non-breaking space.
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 ASCIIandUTF-8strings, the null character is a single zero (0x00) byte. ForUTF-16orUTF-32strings, the null character is 2 or 4 zero bytes respectively.
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 (eg. some
ARMsystems), regardless of the endian-ness of the stored values.
- 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 (eg. a signed 64-bit rational of 0x80000000/0x80000000 evaluates to -1, not +1).
32-bit fixed point values are converted to floating point by treating them
as an integer and dividing by an appropriate value. eg)
16-bit fixed value = 16-bit integer value / 256.0 32-bit fixed value = 32-bit integer value / 65536.0
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
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
The TagName string is 0 to 255 bytes long, and is composed of the
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 (eg. ``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
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
Sets of tags which would require a common prefix should be added in a separate
ExternalFlashType ExternalFlashSerialNumber ExternalFlashFired
one would instead designate a separate ``ExternalFlash''
Type SerialNumber Fired
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
The data value for the
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
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
All elements in a
It is valid to have more than one ``0MIE'' group at the file level, allowing multiple documents in a single
Scanning Backwards through a MIE File
The steps below give an algorithm to quickly locate the last document in a
Read the last 10 bytes of the file. (Note that a valid MIEfile may be as short as 12 bytes long, but a file this length contains only an an emptyMIEgroup.)
- 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.
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 MIEfile.
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
The value of the preceding 4 or 8 bytes gives the length of the complete
file-level MIEgroup (GroupLength). This length includes both the leadingMIEgroup 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 theMIEgroup 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
?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 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
?? ?? ?? ?? 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
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
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.
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 (eg. ``[+|-]DDDDDD''), and multiple values are separated by a single space character (eg. ``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 (eg. ``[+|-]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.
Levels of SupportBasic
- 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 MIEgroup 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. (eg. 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.
EXAMPLESThis section gives examples for working with
Encapsulating Information with Data in a MIE File
The following command encapsulates any file recognized by ExifTool inside a
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
Adding a MIE Trailer to a File
Step 1) Create a
exiftool -o new.mie -trailersignature=1 -tagsfromfile small.jpg \ '-previewimagetype<filetype' '-previewimagesize<imagesize' \ '-previewimagename<filename' '-previewimage<=small.jpg'
Step 2) Append the
cat new.mie >> dst.jpg
Once added, ExifTool may be used to edit or delete a
Multiple MIE Documents in a Single File
# 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 MeasurementSome
exiftool -mie:gpsaltitude='7500(ft)' test.mie
If no units are provided, the default units are written.
Localized TextLocalized 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
2010-04-05 - Fixed "Format Size" Note 7 to give the correct number of bits in the example rational value 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
AUTHORCopyright 2003-2017, 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