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lib/Image/ExifTool/MIE.pm  view on Meta::CPAN

    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:

=over 4

=item 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).

=item 2.

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").

=item 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.

=item 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.

=item 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.

=item 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 (eg. some
ARM systems), regardless of the endian-ness of the stored values.

=item 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 (eg. a signed 64-bit rational of 0x80000000/0x80000000 evaluates to
-1, not +1).

=item 8.

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

=back

=head3 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.

=head3 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.

lib/Image/ExifTool/MIE.pm  view on Meta::CPAN

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
(C<small.jpg>) to a destination JPEG image (C<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.

=head2 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

=head2 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.

=head2 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

=head1 REVISIONS

  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

=head1 AUTHOR

Copyright 2003-2026, Phil Harvey (philharvey66 at gmail.com)

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.

=head1 REFERENCES

=over 4

=item L<https://exiftool.org/MIE1.1-20070121.pdf>

=back

=head1 SEE ALSO

L<Image::ExifTool::TagNames/MIE Tags>, L<Image::ExifTool::MIEUnits>,
L<Image::ExifTool(3pm)|Image::ExifTool>

=cut