| 1 | --------------------------------------------------------------------------------
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| 2 | File: Image/ExifTool/README
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| 3 |
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| 4 | Description: ExifTool support modules documentation
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| 5 |
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| 6 | The ExifTool support modules are loaded by ExifTool to interpret various formats
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| 7 | of meta information.
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| 8 |
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| 9 | The tables in these files are used as lookups based on the tag ID values. The
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| 10 | hash keys are the tag IDs (in decimal or hexadecimal if the ID is numerical as
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| 11 | with EXIF tables, or the tag name if the ID is ASCII as with XMP tables). In
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| 12 | the case of a BinaryData table, the IDs are numerical and specify offsets into
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| 13 | the binary data block. The corresponding hash value provides information about
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| 14 | the tag (explained later).
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| 15 |
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| 16 | Twenty-one special keys (PROCESS_PROC, WRITE_PROC, CHECK_PROC, GROUPS, FORMAT,
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| 17 | FIRST_ENTRY, TAG_PREFIX, PRINT_CONV, DID_TAG_ID, WRITABLE, NOTES, IS_OFFSET,
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| 18 | EXTRACT_UNKNOWN, NAMESPACE, PREFERRED, PARENT, PRIORITY, WRITE_GROUP, LANG_INFO,
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| 19 | VARS and DATAMEMBER) are used to provide additional information about a table.
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| 20 | The special keys have names that are all capitalized to avoid possible conflicts
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| 21 | with tag keys. Below is an explanation of the meaning of each special key:
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| 22 |
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| 23 | PROCESS_PROC : Reference to a function used to process the directory for this
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| 24 | table. If PROCESS_PROC is not given, \&Image::ExifTool::Exif::ProcessExif is
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| 25 | assumed. If PROCESS_PROC is set to 0, the tags are not added to the lookup.
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| 26 | The process proc returns 1 on success or 0 on failure, and takes 3 arguments:
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| 27 | 0) reference to the ExifTool object, 1) reference to a directory information
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| 28 | hash (with the following entries:), 2) reference to the tag table hash.
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| 29 |
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| 30 | Name - Tag name for this SubDirectory entry (for verbose messages)
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| 31 | Base - Base offset for pointers from start of file
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| 32 | DataPt - Reference to data block containing directory (may be undef)
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| 33 | DataPos - Position of data block within file (relative to Base)
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| 34 | DataLen - Length of data block in bytes
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| 35 | DirStart - Offset to start of directory from start of data block
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| 36 | DirLen - Length of directory data within block
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| 37 | DirName - Name of this directory
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| 38 | OutFile - Output file or scalar reference
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| 39 | Parent - Name of parent directory
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| 40 | RAF - Reference to File::RandomAccess object if available
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| 41 | NewDataPos - File position of new data (write proc only)
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| 42 | Fixup - Reference to hash of offset fixups (used in EXIF writing only)
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| 43 | FixBase - Flag set to attempt to fix base offsets
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| 44 | FixOffsets - Evaluated for each value pointer to patch maker note offsets
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| 45 | LastIFD - Used by WriteExif() to return offset of last IFD written
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| 46 | ImageData - Used by WriteExif() to avoid buffering large image data blocks
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| 47 |
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| 48 | WRITE_PROC : Reference to a function to write all new tags for this directory.
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| 49 | The write proc returns the new directory data or undefined on error. It takes
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| 50 | the same arguments as the process proc above except that the second argument
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| 51 | (reference to directory information hash) is optional, and if specified gives
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| 52 | information about the source directory for tags to be copied to the output.
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| 53 |
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| 54 | CHECK_PROC : Reference to a function which validates Raw values for writing.
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| 55 | The function takes three arguments: 0) ExifTool object reference, 1) tagInfo
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| 56 | reference, 2) value reference, and returns undefined (and possibly modifies
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| 57 | the input value) if successful, or an error message if there was a format
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| 58 | problem.
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| 59 |
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| 60 | GROUPS : A hash lookup for the default group names for all entries in this
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| 61 | table. If not specified, the Group 0 and 1 names will be set automatically
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| 62 | according to the name of the module.
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| 63 |
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| 64 | FORMAT : Specifies the default tag Format and corresponding pointer increment
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| 65 | for entries in a BinaryData table, and defaults to 'int8u' if not specified.
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| 66 | The possible values of FORMAT are:
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| 67 |
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| 68 | int8s - Signed 8-bit integer (EXIF 'SBYTE')
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| 69 | int8u - Unsigned 8-bit integer (EXIF 'BYTE')
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| 70 | int16s - Signed 16-bit integer (EXIF 'SSHORT')
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| 71 | int16u - Unsigned 16-bit integer (EXIF 'SHORT')
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| 72 | int32s - Signed 32-bit integer (EXIF 'SLONG')
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| 73 | int32u - Unsigned 32-bit integer (EXIF 'LONG')
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| 74 | int64s - Signed 64-bit integer (BigTIFF 'SLONG8')
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| 75 | int64u - Unsigned 64-bit integer (BigTIFF 'LONG8')
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| 76 | rational32s - Rational consisting of 2 int16s values
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| 77 | rational32u - Rational consisting of 2 int16u values
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| 78 | rational64s - Rational consisting of 2 int32s values (EXIF 'SRATIONAL')
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| 79 | rational64u - Rational consisting of 2 int32u values (EXIF 'RATIONAL')
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| 80 | fixed16s - Signed 16-bit fixed point value
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| 81 | fixed16u - Unsigned 16-bit fixed point value
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| 82 | fixed32s - Signed 32-bit fixed point value
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| 83 | fixed32u - Unsigned 32-bit fixed point value
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| 84 | float - 32-bit IEEE floating point value (EXIF 'FLOAT')
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| 85 | double - 64-bit IEEE floating point value (EXIF 'DOUBLE')
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| 86 | extended - 80-bit extended floating float
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| 87 | ifd - Unsigned 32-bit integer sub-IFD pointer (EXIF 'IFD')
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| 88 | ifd8 - Unsigned 64-bit integer sub-IFD pointer (BigTIFF 'IFD8')
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| 89 | string - Series of 8-bit ASCII characters (EXIF 'ASCII')
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| 90 | undef - Undefined-format binary data (EXIF 'UNDEFINED')
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| 91 | binary - Binary data
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| 92 |
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| 93 | FIRST_ENTRY : Specifies the index for the first tag entry in a binary table.
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| 94 | This value is only used if the Unknown option is set to 2 or higher, and
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| 95 | allows the binary data to be scanned for unknown tag entries.
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| 96 |
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| 97 | TAG_PREFIX : Prefix for names of unknown tags.
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| 98 |
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| 99 | PRINT_CONV : Default print conversion tags where PrintConv isn't specified.
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| 100 |
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| 101 | DID_TAG_ID : Used by GetTagID() as a flag to indicate that TagID's have been
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| 102 | defined for all tags in this table. This may be set in the table definition
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| 103 | to prevent GetTagID() from assigning TagID's.
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| 104 |
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| 105 | WRITABLE : Indicates that all tags in this table are writable. This is the
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| 106 | same as setting the Writable flag for each individual tag in the table, except
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| 107 | for SubDirectory tags which are not made Writable.
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| 108 |
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| 109 | NOTES : Notes to introduce the table in the TagNames documentation. Pod
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| 110 | formatting codes B<> and C<> may be used in this text.
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| 111 |
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| 112 | IS_OFFSET : Reference to list of TagID's representing offsets for binary
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| 113 | data tables only. Not used for EXIF tables.
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| 114 |
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| 115 | EXTRACT_UNKNOWN : Used in PDF tables to specify a directory where all unknown
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| 116 | tags should be extracted.
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| 117 |
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| 118 | NAMESPACE : Namespace prefix for tags in the XMP table. If this isn't a
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| 119 | standard (pre-defined) namespace, then the URI must be defined as well. To do
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| 120 | this, the NAMESPACE value is a reference to either a list or a hash, where the
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| 121 | first element (or hash key) is the namespace prefix and and the second element
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| 122 | (or hash value) is the URI.
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| 123 |
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| 124 | PREFERRED : Set to true if the tags in this table should always be added when
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| 125 | writing information. Overrides the order specified by SetNewGroups(). When
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| 126 | this feature is used, it may also be desireable to specify a preferred group
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| 127 | when calling InitWriteDirs() to write these tags; this avoids creating other
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| 128 | directories for tags which are already being creating in the preferred group.
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| 129 |
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| 130 | PARENT : Used internally to store the parent table name of a user-defined tag
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| 131 | table so the appropriate module can be loaded as required.
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| 132 |
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| 133 | PRIORITY : Default Priority for all tags in this table.
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| 134 |
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| 135 | WRITE_GROUP : Default WriteGroup for all tags in the table.
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| 136 |
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| 137 | LANG_INFO : Code reference to a routine which returns a reference to a
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| 138 | language-specific tag information hash. The routine takes two arguments: a
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| 139 | reference to the non-specific tagInfo hash, and the language code. Used only
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| 140 | in tables which support tag name language extensions (ie. MIE and XMP).
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| 141 |
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| 142 | VARS : Hash used to store additional parameters. Individual modules may use
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| 143 | this to store any parameters they want. The following additional parameters
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| 144 | have been defined, and may be used by any module:
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| 145 |
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| 146 | INDEX - Use "Index" instead of "Tag ID" for column heading in tag name docs.
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| 147 |
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| 148 | NO_ID - Avoid printing "Tag ID" column in tag name documentation.
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| 149 |
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| 150 | DATAMEMBER : BinaryData tables only. A reference to a list of tag ID's which
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| 151 | must be extracted as data members when writing.
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| 152 |
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| 153 | The remaining entries in a tag table are the tag IDs with their associated
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| 154 | information. The information may exist in one of three forms: 1) A simple
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| 155 | scalar which is the name of the tag, 2) A reference to a hash of information
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| 156 | describing this tag, or 3) a reference to a list of hashes which contain
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| 157 | Condition expressions allowing the appropriate hash to be selected to suit the
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| 158 | conditions. The following is a description of possible hash entries. All
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| 159 | entries are optional, except for the tag Name which is required if the tag ID is
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| 160 | numerical.
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| 161 |
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| 162 | Name : The tag name. Tag names need not be unique. If they aren't
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| 163 | unique, duplicate tags overwrite values of previous tags
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| 164 | unless the Duplicates option is set or the new tag has lower
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| 165 | Priority. With Duplicates set, to allow multiple tags with
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| 166 | the same name to exist in the tag information hash, the key of
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| 167 | the previous tag is changed to the form "TagName (N)", where N
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| 168 | starts at 1 and increments for subsequent duplicate tags. A
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| 169 | tag name should start with an uppercase letter, and contain
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| 170 | only the charcters in the set [A-Za-z0-9_-].
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| 171 |
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| 172 | Description : A more readable description of tag name. If a tag doesn't
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| 173 | specify a Description, then the tag Name is used instead, with
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| 174 | spaces inserted between the words.
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| 175 |
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| 176 | Notes : Notes for this tag in the HTML TagNames documentation.
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| 177 |
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| 178 | Groups : Hash lookup for group names for this tag.
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| 179 |
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| 180 | Format : Only valid for BinaryData, EXIF and IPTC tables. For a Binary
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| 181 | or EXIF table, this gives the format that is used to convert
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| 182 | the binary data, and is one of the FORMAT types specified
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| 183 | above. For BinaryData tables, the format may have a size in
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| 184 | trailing brackets which is a perl expression to be evaluated.
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| 185 | The expression may access any of the previous table entries
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| 186 | through a %val hash, or the data size via $size. For example,
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| 187 | 'string[$val{3}]' defines a string with length given by the
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| 188 | table entry with tag index '3'. If not specified, the format
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| 189 | of an EXIF entry is taken from the EXIF information, and the
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| 190 | format of a BinaryData entry is taken from the FORMAT
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| 191 | specified for the table (or int8u if FORMAT is not specified).
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| 192 |
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| 193 | Count : Used when writing EXIF information to specify the number
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| 194 | values to write, or the number of characters in a fixed-length
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| 195 | string. A value of -1 indicates that the count is variable
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| 196 | and should be determined by the number of values provided.
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| 197 | Note that this count that corresponds to the specified Format,
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| 198 | so if a different-sized Writable format is defined, the actual
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| 199 | count written to the file will be different.
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| 200 |
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| 201 | Flags : Flags to specify characteristics for this tag. May be a
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| 202 | simple scalar flag name, a reference to a list of flag names,
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| 203 | or a reference to a hash of flag/value pairs. If not a hash
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| 204 | reference, the flag value is set to 1. Flags are expanded for
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| 205 | faster access at run time into members of the tagInfo hash,
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| 206 | and may be written directly as members if desired. The
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| 207 | available flag names are:
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| 208 |
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| 209 | 'Avoid' - avoid creating this tag if possible.
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| 210 |
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| 211 | 'Binary' - set to 1 for binary data. This has the same effect
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| 212 | as setting ValueConv to '\$val', but it it a bit cleaner and
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| 213 | avoids dummy ValueConvInv entries for writable tags. Has no
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| 214 | effect if ValueConv is defined for the tag.
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| 215 |
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| 216 | 'DataMember' - name of exiftool data member associated with
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| 217 | this tag if it should be stored as a special data member when
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| 218 | writing information. Necessary only if the value of the tag
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| 219 | affects other written information. Currently only used for
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| 220 | tags in EXIF tables.
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| 221 |
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| 222 | 'DataTag' - associated tag name containing data for offset or
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| 223 | byte count tags.
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| 224 |
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| 225 | 'Drop' - set to 1 for tags that should be excluded when
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| 226 | rebuilding maker notes when copying all tags.
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| 227 |
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| 228 | 'EntryBased' - set to 1 if the offset for this value is based
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| 229 | on the IFD entry position. This allows individual values to
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| 230 | be entry-based even though some others aren't (as with the
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| 231 | Casio PrintIM information).
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| 232 |
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| 233 | 'IsOffset' - flag set if the tag represents an offset to some
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| 234 | data, and causes value will be adjusted to an absolute file
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| 235 | offset. If set to 2, the offset base of the parent directory
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| 236 | is used even if the base changes for the current directory
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| 237 | (only some maker notes are this messed up).
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| 238 |
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| 239 | 'List' - indicates that duplicate entries of this tag are
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| 240 | allowed, and will be accumulated in a list. Note that for XMP
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| 241 | information, 3 different types of lists are supported and the
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| 242 | List value specifies the type: 'Bag', 'Seq' or 'Alt'.
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| 243 |
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| 244 | 'MakerNotes' - set if this tag is maker note data.
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| 245 |
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| 246 | 'NotIFD' - set for 'MakerNotes' tags only if the data is not
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| 247 | in standard EXIF IFD format.
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| 248 |
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| 249 | 'OffsetPair' - set if the tag represents half of an offset/
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| 250 | byte count pair. Data for these tags must be handled
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| 251 | separately. Value is the tagID for the paired tag.
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| 252 |
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| 253 | 'Permanent' - flag indicates that a tag is permanent, and
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| 254 | can't be added or deleted from the file. By default, all
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| 255 | MakerNotes tags are permanent unless otherwise specified.
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| 256 |
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| 257 | 'PrintHex' - specifies that unknown PrintConv values should
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| 258 | be printed in hex (ie. 'Unknown (0x0)')
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| 259 |
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| 260 | 'Priority' - gives the priority of this tag while reading. If
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| 261 | set to zero, this tag will not override the value of previous
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| 262 | tags with the same name. If the priority is greater than
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| 263 | zero, this tag won't be overridden by subsequent tags unless
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| 264 | their priority is equal to or greater than this priority. A
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| 265 | special feature is that Priority 0 tags are automatically
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| 266 | incremented to Priority 1 if they exist in the IFD of the full
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| 267 | resolution image (as determined by SubFileType).
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| 268 |
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| 269 | 'Protected' - bit mask to protect tags from writing:
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| 270 | Bit 0x01 indicates an 'unsafe' tag, which is not set via
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| 271 | SetNewValuesFromFile() unless specified explicitly.
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| 272 | Bit 0x02 indicates a 'protected' tag, which should not be set
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| 273 | directly by the user.
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| 274 |
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| 275 | 'SeparateTable' - set to list PrintConv values in a separate
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| 276 | table in the HTML documentation. Value is 1 for a table name
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| 277 | of 'Module TagName', or 'TAG' for 'Module TAG', or 'MODULE
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| 278 | TAG' to fully specify the table name.
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| 279 |
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| 280 | 'SetResourceName' - [Photoshop tags only] set to 1 to append
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| 281 | resource name to the extracted value (ie. 'VALUE/#NAME#/').
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| 282 | Also allows resource name to be appended when writing new
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| 283 | values. May be set to any value other than 1 for a default
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| 284 | resource name to use when writing if an appended name is not
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| 285 | provided.
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| 286 |
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| 287 | 'SubIFD' - used in writing to determine that the tag specifies
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| 288 | an offset to a sub-IFD. When this flag is set, the Group1
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| 289 | name gives the name of the IFD.
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| 290 |
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| 291 | 'Unknown' - this is an unknown tag (only extracted when the
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| 292 | Unknown option is set).
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| 293 |
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| 294 | RawConv : Used to convert the Raw value at extraction time (while the
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| 295 | image file is still open, unlike ValueConv and PrintConv below
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| 296 | which are done later only if the value is requested). May be
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| 297 | a scalar expression using $val (the Raw tag value), $self (the
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| 298 | current ExifTool object) and $tag (the tag name), or a code
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| 299 | reference with $val and $self as arguments. For Composite
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| 300 | tags, $val is a reference to a hash of component tag names,
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| 301 | and @val may be used to access the Raw values of these tags.
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| 302 | The returned value may be a scalar which is used as the new
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| 303 | Raw value, a scalar reference to a binary data value, a hash
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| 304 | reference for Composite tags, an ARRAY reference for a list of
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| 305 | values, or undefined to indicate that the tag should be
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| 306 | ignored. Also, RawConv may generate Warning or Error tags,
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| 307 | while ValueConv and PrintConv may not. Note: RawConv should
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| 308 | only be used if necessary (in general, only if the tag may be
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| 309 | ignored). It is preferable to use ValueConv instead of
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| 310 | RawConv because ValueConv is only executed if the tag value is
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| 311 | requested, while RawConv is executed for all extracted tags.
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| 312 |
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| 313 | ValueConv : Used to convert the Raw value to a useable form. May be a hash
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| 314 | reference to act as a lookup table, a scalar which is
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| 315 | evaluated as a Perl expression, or a code reference to a
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| 316 | subroutine. May also be a list reference, in which case the
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| 317 | value is split at whitespace into a list of values and each
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| 318 | value is converted by the associated entry in the ValueConv
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| 319 | list. If a hash reference is used and the Raw value doesn't
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| 320 | appear as one of the keys, then the converted value is set to
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| 321 | "Unknown (X)", where X is the Raw value (unless a special
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| 322 | 'BITMASK' key exists, in which case the hash referenced by
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| 323 | 'BITMASK' is used to decode individual value bits). In an
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| 324 | expression, $self is a reference to the current ExifTool
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| 325 | object, $val is the Raw value, and $tag is the tag name. The
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| 326 | subroutine takes 2 arguments: the Raw value and a reference to
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| 327 | the current ExifTool object. The expression or subroutine is
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| 328 | evaluated when and if the tag value is requested (ie. only
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| 329 | after all extraction is complete), so if necessary at this
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| 330 | time the values of all other tags are available via calls to
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| 331 | $self->GetValue("Tag","Raw"). (Note: In theory, types other
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| 332 | than "Raw" may be accessed, but they are slower and may lead
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| 333 | to cyclical dependencies so they should be avoided). When
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| 334 | evaluated, the expression or subroutine returns a scalar for
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| 335 | the converted value, or a scalar reference to a binary data
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| 336 | value (see the 'Binary' flag). The return value should always
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| 337 | be defined -- use RawConv instead to return undef if it is
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| 338 | necessary to test the value for validity, otherwise an undef
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| 339 | tag may hide a previously defined value when the Duplicates
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| 340 | option is not enabled. Composite tags which Require or Desire
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| 341 | other tags may access the ValueConv, PrintConv and Raw values
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| 342 | of these tags through the elements of the @val, @prt and @raw
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| 343 | lists respectively (only if there was no RawConv or returned a
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| 344 | hash reference). For these tags, $val may be used in an
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| 345 | expression to represent $val[0], and the first argument passed
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| 346 | for a code reference is a reference to @val. If ValueConv is
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| 347 | not specified, the Raw value is not converted.
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| 348 |
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| 349 | PrintConv : This entry is similar to ValueConv above, except that it is
|
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| 350 | used to further convert the tag value to a human readable
|
|---|
| 351 | form. It can be either a hash lookup, a scalar Perl
|
|---|
| 352 | expression, a code reference or a list reference. In this
|
|---|
| 353 | expression, $self, $val and $tag may be used as with
|
|---|
| 354 | ValueConv, but if ValueConv was defined then $val is the
|
|---|
| 355 | ValueConv value instead of the Raw value. The returned value
|
|---|
| 356 | should always be defined. Note that the print conversion is
|
|---|
| 357 | only done if the PrintConv option is enabled (which it is by
|
|---|
| 358 | default), and if the result of the ValueConv is not a scalar
|
|---|
| 359 | reference. If it is a list reference, then the converted
|
|---|
| 360 | values are joined by '; ' in the output string.
|
|---|
| 361 |
|
|---|
| 362 | RawConvInv : The inverse of RawConv. This should only be used in very rare
|
|---|
| 363 | situations when the raw value can not be predetermined.
|
|---|
| 364 | Unlike the other inverse conversions which are applied in
|
|---|
| 365 | SetNewValue(), this conversion is applied in WriteInfo() as
|
|---|
| 366 | the file is being written. This is important because it means
|
|---|
| 367 | that FILE_TYPE and any DataMember tags ocurring before this
|
|---|
| 368 | tag in the file are available. Beware that if the return
|
|---|
| 369 | value is not defined, the tag will be deleted unless there is
|
|---|
| 370 | specific logic to avoid this (currently, only EXIF and Binary
|
|---|
| 371 | data directories handle this case).
|
|---|
| 372 |
|
|---|
| 373 | ValueConvInv : The inverse of ValueConv. Only necessary for Writable tags
|
|---|
| 374 | when ValueConv is specified (except WriteAlso tags). Note
|
|---|
| 375 | that DataMember tags may NOT be used in the inverse
|
|---|
| 376 | conversions because these conversions are done before the
|
|---|
| 377 | input file is parsed. Instead, a Condition or RawConvInv must
|
|---|
| 378 | be used.
|
|---|
| 379 |
|
|---|
| 380 | PrintConvInv : The inverse of PrintConv. Only necessary if for Writable tags
|
|---|
| 381 | when PrintConv is specified (unless WriteAlso is used).
|
|---|
| 382 |
|
|---|
| 383 | Condition : If given, specifies scalar which is evaluated as a Perl
|
|---|
| 384 | expression at extraction time to decide whether the tag is
|
|---|
| 385 | valid. If used in a list of alternate tag definitions, the
|
|---|
| 386 | first list entry with a true condition is taken. If no
|
|---|
| 387 | condition exists, then a 'true' condition is assumed. The
|
|---|
| 388 | expression may use $self to access the ExifTool object, and
|
|---|
| 389 | $oldVal to access the previous Raw value of the tag (if it
|
|---|
| 390 | exists). The first 48 bytes of the raw data value are
|
|---|
| 391 | accessible through the reference $valPt for EXIF and Jpeg2000
|
|---|
| 392 | tags only. EXIF tags may also reference the format string and
|
|---|
| 393 | value count through $format and $count. Note that if the
|
|---|
| 394 | value is writable and $valPt is used, the tag must have a
|
|---|
| 395 | Format (unless 'undef' or 'string'), and a Count (unless 1 or
|
|---|
| 396 | length of the 'undef' or 'string'), so the raw data may be
|
|---|
| 397 | generated for evaluating the Condition.
|
|---|
| 398 |
|
|---|
| 399 | Require : [Composite tags only] A hash reference specifying the tags
|
|---|
| 400 | required to calculate the composite tag value. The hash
|
|---|
| 401 | values are the names of the required tags, and the keys
|
|---|
| 402 | specify the indices where the tag values are stored in the
|
|---|
| 403 | @val list used in the ValueConv and/or PrintConv expression.
|
|---|
| 404 | The composite value is only calculated if the values for all
|
|---|
| 405 | Require'd tags are defined. Require and Desire tag names may
|
|---|
| 406 | be prefixed by an optional group family 0 or 1 name followed
|
|---|
| 407 | by a colon. Case IS significant. A special feature allows
|
|---|
| 408 | a scalar tag name to be used instead of the hash reference
|
|---|
| 409 | when only the 0th tag is defined. For example, the following
|
|---|
| 410 | two definitions are equivalent:
|
|---|
| 411 |
|
|---|
| 412 | Require => { 0 => 'XMP:Title' },
|
|---|
| 413 | Require => 'XMP:Title',
|
|---|
| 414 |
|
|---|
| 415 | Desire : [Composite tags only] This is the same as Require except that
|
|---|
| 416 | the value is still calculated even if the specified tags don't
|
|---|
| 417 | exist. Beware that the elements of @val, @prt and @raw may be
|
|---|
| 418 | undefined for Desire'd tags. Both Require and Desire may
|
|---|
| 419 | exist together, however be sure to specify unique keys for
|
|---|
| 420 | each tag since they are used as indices into the @val, @prt
|
|---|
| 421 | and @raw lists common to both Require'd and Desire'd tags.
|
|---|
| 422 |
|
|---|
| 423 | Shift : [Writable tags only] Specifies type of shift to apply if this
|
|---|
| 424 | value may be shifted. Set to 'Time' for shifting date/time
|
|---|
| 425 | tags.
|
|---|
| 426 |
|
|---|
| 427 | Writable : Indicates this tag can be written (or not written if value is
|
|---|
| 428 | set to zero), and for EXIF-type tables gives format for
|
|---|
| 429 | writing. Writable may be set to 1 for MakerNotes information
|
|---|
| 430 | because the existing format is always used, however providing
|
|---|
| 431 | a format is desireable because it is used in validating the
|
|---|
| 432 | value. For EXIF tables, the Writable flag may be different
|
|---|
| 433 | than the Format flag, in which case Format is used for
|
|---|
| 434 | converting the binary value and Writable specifies the format
|
|---|
| 435 | code written to the EXIF IFD. For SubDirectories in EXIF
|
|---|
| 436 | information, this flag is only defined if the SubDirectory is
|
|---|
| 437 | writable as a block, or if the SubDirectory can not be edited
|
|---|
| 438 | (in which case Writable is set to 0).
|
|---|
| 439 |
|
|---|
| 440 | WriteAlso : Used for writable tag to specify other tags to write when this
|
|---|
| 441 | tag is written. The value is a hash reference. The hash keys
|
|---|
| 442 | are the names of the tags to write, and the values are
|
|---|
| 443 | evaluated to obtain the ValueConv values of each tag (or undef
|
|---|
| 444 | to delete the tag). In the eval, $val may be used as the Raw
|
|---|
| 445 | value of the parent tag. This will write Protected tags that
|
|---|
| 446 | aren't directly writable (Protected bit 0x02 set).
|
|---|
| 447 |
|
|---|
| 448 | WriteCheck : If given, specifies a scalar which is evaluated as a Perl
|
|---|
| 449 | expression for a one-time validatation the value being
|
|---|
| 450 | written. The expression has access to 3 variables: $val is
|
|---|
| 451 | the value to be written, $self is the ExifTool object, and
|
|---|
| 452 | $tagInfo is the tag information hash reference. It returns an
|
|---|
| 453 | error string or undef if the value is good.
|
|---|
| 454 |
|
|---|
| 455 | WriteCondition: [Writable EXIF tags only] Specifies a condition to be
|
|---|
| 456 | evaluated before the tag can be written to a specific file.
|
|---|
| 457 | The condition may use $self to reference the ExifTool object,
|
|---|
| 458 | and returns true if it is OK for writing. Unlike WriteCheck
|
|---|
| 459 | which is done only once when the new value is set, this
|
|---|
| 460 | condition is evaluated before the information is written in
|
|---|
| 461 | each file.
|
|---|
| 462 |
|
|---|
| 463 | WriteGroup : [Required for writable EXIF tags] Specifies the IFD where the
|
|---|
| 464 | information gets written by default.
|
|---|
| 465 |
|
|---|
| 466 | OffsetPair : Used in EXIF table to specify the tagID for the corresponding
|
|---|
| 467 | offset or length tag.
|
|---|
| 468 |
|
|---|
| 469 | DataTag : Used in EXIF table to specify the tag name of the data
|
|---|
| 470 | associated with offset/length tags.
|
|---|
| 471 |
|
|---|
| 472 | Struct : [XMP tags only] Used by XMP writer code to specify name of XMP
|
|---|
| 473 | structure so the PropertyPath can be determined.
|
|---|
| 474 |
|
|---|
| 475 | Units : [MIE tags only] Reference to a list of valid units strings.
|
|---|
| 476 | The default units are the first item in the list.
|
|---|
| 477 |
|
|---|
| 478 | TagID : [reserved] This entry is used internally by GetTagID() to
|
|---|
| 479 | cache tag ID numbers for speed.
|
|---|
| 480 |
|
|---|
| 481 | Table : [reserved] Reference to parent tag table.
|
|---|
| 482 |
|
|---|
| 483 | PropertyPath : [reserved] Used internally by XMP writer to save property path
|
|---|
| 484 | name.
|
|---|
| 485 |
|
|---|
| 486 | Module : [reserved] Used internally to store module name for writable
|
|---|
| 487 | Composite tags.
|
|---|
| 488 |
|
|---|
| 489 | LangCode : [reserved] Used internally to indicate language code for
|
|---|
| 490 | alternate language tags (MIE and XMP only)
|
|---|
| 491 |
|
|---|
| 492 | SubDirectory { If it exists, this specifies the start of a new subdirectory.
|
|---|
| 493 | It contains a collection of variables which specify the type
|
|---|
| 494 | and location of the subdirectory. These variables are
|
|---|
| 495 | described below:
|
|---|
| 496 |
|
|---|
| 497 | TagTable : Specifies the name of the tag table lookup for the new
|
|---|
| 498 | subdirectory. If not specified, the parent tag table is used.
|
|---|
| 499 |
|
|---|
| 500 | Start : The offset to the start of the subdirectory relative to the
|
|---|
| 501 | current Base. This is a Perl expression which may use
|
|---|
| 502 | $valuePtr to represent the location of the tag value in the
|
|---|
| 503 | file, or $val for the value itself. If not specified, a Start
|
|---|
| 504 | of '$valuePtr' is assumed.
|
|---|
| 505 |
|
|---|
| 506 | OffsetPt : If specified, this is a Perl expression that gives the
|
|---|
| 507 | position of a 32-bit word in the current directory that is
|
|---|
| 508 | added to the Start position to get the position of the new
|
|---|
| 509 | subdirectory. The expression should use the position of the
|
|---|
| 510 | current tag ($valuePtr).
|
|---|
| 511 |
|
|---|
| 512 | Base : This specifies the base offset for all pointers in the
|
|---|
| 513 | subdirectory. This need not be specified if the offset is the
|
|---|
| 514 | same as the current directory, which is normally the case.
|
|---|
| 515 | May use $start to represent the subdirectory start location
|
|---|
| 516 | relative to the current base. If this is defined, the
|
|---|
| 517 | automatic validation of base offsets is disabled for maker
|
|---|
| 518 | notes directories.
|
|---|
| 519 |
|
|---|
| 520 | EntryBased : Flag indicating that the offsets are based on the indidual
|
|---|
| 521 | directory entry position, so offsets are incremented by 12
|
|---|
| 522 | times the corresponding entry index.
|
|---|
| 523 |
|
|---|
| 524 | MaxSubdirs : Maximum number of subdirectories specified by the current tag
|
|---|
| 525 | (if the tag specifies multiple values). If not specified, the
|
|---|
| 526 | tag value ($val) is used as-is. If MaxSubdirs is specified,
|
|---|
| 527 | then one subdirectory is parsed for each value found up to the
|
|---|
| 528 | maximum number specified.
|
|---|
| 529 |
|
|---|
| 530 | ByteOrder : Specifies byte ordering if different than than the rest of the
|
|---|
| 531 | file. Must be either BigEndian, LittleEndian or Unknown. If
|
|---|
| 532 | Unknown is specified, the byte order will be determined from
|
|---|
| 533 | the directory count (however, this can not be done if OffsetPt
|
|---|
| 534 | is specified).
|
|---|
| 535 |
|
|---|
| 536 | Validate : If given, specifies Perl expression which is used to validate
|
|---|
| 537 | the subdirectory data. The following variables may be used in
|
|---|
| 538 | the expression: $val (value of the tag), $dirData (reference
|
|---|
| 539 | to directory data), $subdirStart (offset to subdirectory
|
|---|
| 540 | start) and $size (size of subdirectory).
|
|---|
| 541 |
|
|---|
| 542 | ProcessProc: If given, specifies processing procedure used to decode this
|
|---|
| 543 | subdirectory data. This overrides the default procedure
|
|---|
| 544 | specified by PROCESS_PROC in the tag table.
|
|---|
| 545 |
|
|---|
| 546 | DirName : Name of this subdirectory. If not specified, the name is
|
|---|
| 547 | taken from the tag name. DirName is important because it is
|
|---|
| 548 | used when writing to compare against names in the directory
|
|---|
| 549 | map to determine which directories need to be edited.
|
|---|
| 550 |
|
|---|
| 551 | FixBase : Flag set if base offsets should be fixed. Used to add a
|
|---|
| 552 | constant to maker notes offsets to fix damage done by some
|
|---|
| 553 | image editing utilities. (maker notes only)
|
|---|
| 554 |
|
|---|
| 555 | FixOffsets : Expression to evaluate for each value pointer to patch
|
|---|
| 556 | problems with some EXIF maker note offsets. May access the
|
|---|
| 557 | following variables: $valuePtr, $valEnd, $size, $tagID and
|
|---|
| 558 | $wFlag. May return undef when writing to ignore the entry.
|
|---|
| 559 | }
|
|---|
| 560 |
|
|---|
| 561 | --------------------------------------------------------------------------------
|
|---|
