# The Image::ExifTool Perl Library Module

## Description

The Image::ExifTool library provides an extensible set of Perl modules to read and write meta information in a wide variety of image, audio and video files.

## Index

The following sections of this document give examples of how to use Image::ExifTool, and explain the following individual functions in more detail:

ImageInfo new Options ClearOptions ExtractInfo GetInfo WriteInfo CombineInfo GetTagList GetFoundTags GetRequestedTags GetValue | SetNewValue SetNewValuesFromFile GetNewValues CountNewValues SaveNewValues RestoreNewValues SetFileModifyDate SetFileName SetNewGroups GetNewGroups GetTagID GetDescription | GetGroup GetGroups BuildCompositeTags GetTagName GetShortcuts GetAllTags GetWritableTags GetAllGroups GetDeleteGroups GetFileType CanWrite CanCreate

## Using ExifTool

The ExifTool module may be used by simply calling the ImageInfo function:

>     use Image::ExifTool qw(:Public);
>     my $info = ImageInfo('image.jpg');

or in a more object-oriented fashion, by creating an ExifTool object:

>     use Image::ExifTool qw;
>     my $exifTool = new Image::ExifTool;
>     my $info = $exifTool->ImageInfo('image.jpg');

The object-oriented method allows more flexibility, but is slightly more complicated. You choose the method that you prefer.

The $info value returned by ImageInfo in the above examples is a reference to a hash containing the tag/value pairs. Here is a simplified example which prints out this information:

>     foreach (keys %$info) {
>         print "$_ => $$info{$_}\n";
>     }

See ImageInfo for a more detailed description of the info hash entries.

And the technique for writing meta information is equally simple:

>     use Image::ExifTool;
>     my $exifTool = new Image::ExifTool;
>     $exifTool->SetNewValue(Author => 'Phil Harvey');
>     $exifTool->WriteInfo('image.jpg','modified_image.jpg');

## Configuration

User-defined tags can be added via the ExifTool configuration file. See "ExifTool_config" in the ExifTool distribution for more details. If necessary, the configuration feature can be disabled by setting the ExifTool "noConfig" flag before loading Image::ExifTool. ie)

>     BEGIN { $Image::ExifTool::noConfig = 1 }
>     use Image::ExifTool;

## ImageInfo

Obtain meta information from image. This is the one-step function for obtaining meta information from an image. Internally, ImageInfo calls ExtractInfo to extract data from the image, and GetInfo and GetTagList to generate the returned information hash and tag list.

> Prototype | ImageInfo($;@)
> Inputs | 0) [optional] ExifTool object reference 1) File name, file reference or scalar reference 2-N) [optional] list of tag names to find (or tag list reference or options reference, see below)
> Returns | Reference to hash of tag key/value pairs

Examples:

> Non object-oriented example showing use of options and returning tag list:

>     use Image::ExifTool qw(ImageInfo);
>     my @ioTagList;
>     my $info;

>     $info = ImageInfo('image.jpg', \@ioTagList, {Sort => 'Group0'});

> Object-oriented example to read from a file that is already open:

>     my $exifTool = new Image::ExifTool;

>     $info = $exifTool->ImageInfo(\*FILE_PT, 'Aperture', 'ShutterSpeed', 'ISO');

> Extract information from an image in memory:

>     $info = $exifTool->ImageInfo(\$imageData);

> Extract information from an embedded thumbnail image:

>     $info = ImageInfo('image.jpg', 'thumbnailimage');
>     my $thumbInfo = ImageInfo($$info{ThumbnailImage});

> Using an ExifTool object to set the options before calling ImageInfo:

>     my $filename = shift || die "Please specify filename\n";
>     my @ioTagList = qw(filename imagesize xmp:creator exif:* -ifd1:*);

>     $exifTool->Options(Unknown => 1, DateFormat => '%H:%M:%S %a. %b. %e, %Y');
>     $info = $exifTool->ImageInfo($filename, \@ioTagList);

Function Arguments:

ImageInfo is very flexible about the arguments passed to it, and interprets them based on their type. It may be called with one or more arguments. The one required argument is either a SCALAR (the image file name), a file reference (a reference to the image file) or a SCALAR reference (a reference to the image in memory). Other arguments are optional. The order of the arguments is not significant, except that the first SCALAR is taken to be the file name unless a file reference or scalar reference comes earlier in the argument list.

Below is a more detailed explanation of how the ImageInfo function arguments are interpreted.

> ExifTool ref | ImageInfo may be called with an ExifTool object if desired. The advantage of using the object-oriented form of this function is that after ImageInfo returns, you may use the object-oriented functions below to obtain additional information if required. Must be the first argument if used.
> SCALAR | The first scalar argument is taken to be the file name unless an earlier argument specified the image data via a file reference (file ref) or data reference (SCALAR ref). The remaining scalar arguments are names of tags for requested information. If no tags are specified, all possible information is extracted. Tag names are case-insensitive and may be prefixed by an optional group name followed by a colon. The group name may begin with a family number (ie. '`1IPTC:Keywords`'), to restrict matches to a specific family. A tag name of '`*`' may be used, thus allowing '`GROUP:*`' to represent all tags in a specific group, or a group name of '`*`' may be used, in which case all available instances of the specified tag are returned regardless of the Duplicates setting (ie. '`*:WhiteBalance`'). And finally, a leading '`-`' indicates tags to be excluded (ie. '`-IFD1:*`'). Note that keys in the returned information hash and elements of the returned tag list are not necessarily the same as these tag names -- group names are removed, the case may be changed, and an instance number may be added. For this reason it is best to use either the keys of the returned hash or the elements of the tag array when accessing the tag values. See the TagNames documentation for a complete list of ExifTool tag names.
> File ref | A reference to an open image file. If you use this method (or a SCALAR reference) to access information in an image, the FileName and Directory tags will not be returned. (Also, the FileSize and FileModifyDate tags will not be returned unless it is a plain file.) Image processing begins at the current file position, and on return the file position is unspecified.
> SCALAR ref | A reference to image data in memory.
> ARRAY ref | Reference to a list of tag names. On entry, any elements in the list are added to the list of requested tags. On return, this list is updated to contain an ordered list of tag keys for all extracted tags.
> HASH ref | Reference to a hash containing the options settings. See Options documentation below for a list of available options. Options specified as arguments to ImageInfo take precedence over Options settings.

Return Value:

ImageInfo returns a reference to a hash of tag key/value pairs. The tag keys are identifiers, which are similar to the tag names but may have an embedded instance number if multiple tags with the same name were extracted from the image. Many of the ExifTool functions require a tag key as an argument. Use GetTagName to get the tag name for a given tag key. Note that the case of the tag names may not be the same as requested.

Values of the returned hash are usually simple scalars, but a scalar reference is used to indicate binary data and an array reference may be used to indicate a list. Lists of values are joined by commas into a single string if and only if the PrintConv option is enabled and the List option is disabled (which are the defaults). Note that binary values are not necessarily extracted unless specifically requested or the Binary option is set. If not extracted the value is a reference to a string of the form "`Binary data ##### bytes`".

Here is a simple example to print out the information returned by ImageInfo. It shows how to print out a human-friendly output for all returned tag values, and works for either setting of the PrintConv option (although binary data will be printed to the console if PrintConv is disabled):

>     foreach (keys %$info) {
>         my $val = $$info{$_};
>         if (ref $val eq 'ARRAY') {
>             $val = join(', ', @$val);
>         } elsif (ref $val eq 'SCALAR') {
>             $val = '(Binary data)';
>         }
>         printf("%-24s : %s\n", $_, $val);
>     }

and gives output like this (PrintConv enabled):

>     WhiteBalance             : Auto
>     FNumber                  : 3.5
>     InteroperabilityOffset   : 936
>     XResolution              : 72
>     ISO                      : 100
>     ThumbnailImage           : (Binary data)
>     FlashOn                  : On
>     Make                     : FUJIFILM
>     ShutterSpeedValue        : 1/64
>     ExposureCompensation     : 0
>     Sharpness                : Soft
>     ResolutionUnit           : inches

Notes:

As well as tags representing information extracted from the image, the following tags generated by ExifTool may be returned:

> ExifToolVersion | The ExifTool version number
> Error | An error message if the image could not be read
> Warning | A warning message if problems were encountered while extracting information

## new

Create a new ExifTool object.

Example:

>     my $exifTool = new Image::ExifTool;

Note that ExifTool uses AUTOLOAD to load non-member methods, so any class using Image::ExifTool as a base class must define an AUTOLOAD which calls Image::ExifTool::DoAutoLoad(). ie)

>     sub AUTOLOAD
>     {
>         Image::ExifTool::DoAutoLoad($AUTOLOAD, @_);
>     }

The following functions require an ExifTool object as the first argument

## Options

Get/set ExifTool options. This function can be called to set the default options for an ExifTool object. Options set this way are in effect for all function calls but may be overridden by options passed as arguments to a specific function.

> Prototype | Options($$;@)
> Inputs | 0) ExifTool object reference 1) Parameter name (see table below) 2) [optional] Option value if specified (may be undef to clear option) 3-N) [optional] Additional parameter/value pairs
> Returns | Previous value of last specified parameter

Available options:

> ExifTool Options
> Option | Description | Values | Default
> --- | --- | --- | ---
> Binary | Flag to extract the value data for all binary tags. Tag values representing large binary data blocks (ie. ThumbnailImage) are not necessarily extracted unless this option is set or the tag is specifically requested by name. | 0 or 1 | 0
> ByteOrder | The byte order for newly created EXIF segments when writing. Note that if EXIF information already exists, the existing order is maintained. If ByteOrder is not defined, then the order of the maker notes is used (if they are being copied), otherwise big-endian ('MM') order is assumed. This can also be set via the ExifByteOrder tag, but the ByteOrder option takes precedence if both are set. | 'MM','II' or undef | undef
> Charset | Character set for converting special characters. Note that this option affects some types of information when reading/writing the file and other types when getting/setting tag values, so it must be defined for both types of access. |
> UTF8 - | UTF-8 characters
> Latin - | Windows Latin1 (cp1252)
> | 'UTF8'
> Compact | Flag to write compact output. The XMP specification suggests that the data be padded with blanks to allow in-place editing. By setting this flag, 2kB is saved for files with XMP data. | 0 or 1 | 0
> Composite | Flag to calculate Composite tags | 0 or 1 | 1
> Compress | Flag to write new values in compressed format if possible. Has no effect unless Compress::Zlib is installed. | 0 or 1 | 0
> CoordFormat | Format for GPS coordinates | Format for printing GPS coordinates. This is a printf format string with specifiers for degrees, minutes and seconds in that order, however minutes and seconds may be omitted. The default is equivalent to using a format string of `q{%d deg %d' %.2f"}`. | undef
> DateFormat | Format for date/time | See strftime manpage for details | undef
> Duplicates | Flag to save duplicate tag values | 0 or 1 | 1
> Exclude | Exclude specified tags | Tag name or reference to a list of tag names to exclude. Case is not significant. Tags may also be excluded by preceding their name with a '-' in the arguments to ImageInfo. | undef
> FastScan | Flag to increase speed of extracting information from JPEG images. With this option set, ExifTool will not scan to the end of a JPEG image to check for an AFCP, CanonVRD, FotoStation, PhotoMechanic, MIE or PreviewImage trailer. Also, when combined with the ScanForXMP option, prevents scanning for XMP in recognized file types. | 0 or 1 | 0
> FixBase | Fix maker notes base offset. Allows values to be extracted from maker notes which have been corrupted by editing with 3rd party software. | An integer specifying a value to be added to the maker notes base offset, or the empty string ('') for ExifTool to take its best guess at the correct base. | undef
> Group# | Extract tags for specified groups | Group name or reference to list of group names. Group name may begin with '-' to exclude a group. Case IS significant. See GetAllGroups for a list of available groups. | undef
> HtmlDump | Dump information in hex to a dynamic HTML web page. Option value sets a limit on the maximum block size. Output file is specified by the TextOut option. |
> 0 = | No HTML dump
> 1 = | 1 KB size limit
> 2 = | 16 KB size limit
> 3 = | Full dump
> | 0
> HtmlDumpBase | Specifies the base for HTML dump offsets. If not defined, the EXIF/TIFF base offset is used. |
> 0 = | Absolute offsets
> non-zero = | Relative offsets
> undef = | EXIF/TIFF offsets
> | undef
> IgnoreMinorErrors | Flag to ignore minor errors. Causes minor errors to be downgraded to warnings, and minor warnings to be ignored. This option is provided mainly to allow writing of files when minor errors occur, but also allows thumbnail and preview images to be extracted even if they don't have a recognizable header. | 0 or 1 | 0
> List | Flag to extract lists of PrintConv values into arrays instead of concatenating them into comma-separated strings. | 0 or 1 | 0
> MakerNotes | Option to extract MakerNotes and other writable subdirectories (such as PrintIM) as a data block. Normally when the MakerNotes are extracted they are rebuilt to include data outside the boundaries of the original maker note data block, but a value of 2 disables this feature. |
> 0 = | Don't extract writable subdirectories
> 1 = | Extract and rebuild makernotes into self-contained block
> 2 = | Extract without rebuilding makernotes
> | 0
> MissingTagValue | Value for missing tags in expressions evaluated by SetNewValuesFromFile. If not set, a minor error is issued for missing values, or the value is set to '' if IgnoreMinorErrors is set. | Any string, or undef | undef
> PrintConv | Flag to enable print conversion. Also enables inverse print conversion for writing. | 0 or 1 | 1
> ScanForXMP | Flag for scan all files (even unrecognized formats) for XMP information unless XMP was already found in the file. When combined with the FastScan option, only unrecognized file types are scanned for XMP. | 0 or 1 | 0
> Sort | Specifies order to sort tags in the returned tag list |
> Input | Sort in same order as input tag arguments
> Alpha | Sort alphabetically
> File | Sort in order that tags were found in the file
> Group# | Sort by tag group, where # is the group family number. If # is not specified, Group0 is assumed. See GetAllGroups for a group list.
> | 'Input'
> StrictDate | Flag to return undefined value for any date which can't be converted when the DateFormat option is used. | 0 or 1 | 0
> TextOut | Output file for Verbose and HtmlDump options. | File reference | \*STDOUT
> Unknown | Control extraction of unknown tags |
> 0 = | Unknown tags not extracted
> 1 = | Unknown tags are extracted from EXIF (and other tagged-format) directories
> 2 = | Unknown tags also extracted from binary data blocks
> | 0
> Verbose | Print verbose messages to file specified by TextOut option. Click here for example outputs. |
> 0 = | No verbose messages
> 1 = | Print tag names and raw values
> 2 = | Add additional tag details
> 3 = | Add hex dump of tag data (with length limits)
> 4 = | Remove length limit on dump of tag values
> 5 = | Remove length limit on dump of JPEG segments
> | 0

Examples:

>     $exifTool->Options(Exclude => 'OwnerName');

>     $exifTool->Options(Group0 => ['EXIF', 'MakerNotes']);

>     $exifTool->Options(Group1 => '-IFD1');  # ignore IFD1 tags

>     $exifTool->Options(Sort => 'Group2', Unknown => 1);

>     my $oldSetting = $exifTool->Options(Duplicates => 0);

>     my $isVerbose = $exifTool->Options('Verbose');

## ClearOptions

Reset all options to their default values.

> Prototype | ClearOptions()
> Inputs | 0) ExifTool object reference

## ExtractInfo

Extract all meta information from an image.

> Prototype | ExtractInfo($;@)
> Inputs | 0) ExifTool object reference 1-N) Same as ImageInfo except that a list of tag keys is not returned if an ARRAY reference is given.
> Returns | 1 if this was a valid image, 0 otherwise

The following options are effective in the call to ExtractInfo:

> Binary, Composite, DateFormat, Unknown and Verbose.

Example:

>     $success = $exifTool->ExtractInfo('image.jpg', \%options);

## GetInfo

GetInfo is called to return meta information after it has been extracted from the image by a previous call to ExtractInfo or ImageInfo. This function may be called repeatedly after a single call to ExtractInfo or ImageInfo.

> Prototype | GetInfo($;@)
> Inputs | 0) ExifTool object reference 1-N) Same as ImageInfo except that an image can not be specified
> Returns | Reference to information hash, the same as with ImageInfo

Examples:

>     $info = $exifTool->GetInfo('ImageWidth', 'ImageHeight');

>     $info = $exifTool->GetInfo(\@ioTagList);

>     $info = $exifTool->GetInfo({Group2 => ['Author', 'Location']});

The following options are effective in the call to GetInfo:

> Duplicates, Exclude, Group#, PrintConv (and Sort if tag list reference is given).

## WriteInfo

Write meta information to a file. The specified source file is rewritten to the same-type destination file with new information as specified by previous calls to SetNewValue. The necessary segments and/or directories are created in the destination file as required to store the specified information. May be called repeatedly to write the same information to additional files without the need to call SetNewValue again.

> Prototype | WriteInfo($$;$$)
> Inputs | 0) ExifTool object reference 1) Source file name, file reference, scalar reference, or undefined to create a file from scratch 2) [optional] Destination file name, file or scalar reference 3) [optional] Destination file type
> Returns | 1 if file was written OK, 2 if file was written but no changes made, 0 on file write error.

The source file name may be undefined to create a file from scratch (currently only XMP, ICC and MIE files can be created in this way). If undefined, the destination file type is required unless the type can be determined from the destination file name.

The destination file name may be undefined to edit a file in place (make sure you have backups!). If a destination file name is given, the specified file must not exist because existing destination files will not be overwritten.

The destination file type is only used if the source file is undefined.

Examples:

>     # add information to a source file, writing output to new file
>     my $result = $exifTool->WriteInfo($srcfile, $dstfile);

>     # create XMP data file from scratch
>     $exifTool->WriteInfo(undef, $dstfile, 'XMP');

>     # edit file in place (you do have backups, right?)
>     $exifTool->WriteInfo($srcfile);

>     # retrieve error and warning messages
>     $errorMessage = $exifTool->GetValue('Error');
>     $warningMessage = $exifTool->GetValue('Warning');

If an error code is returned, an Error tag is set and GetValue('Error') can be called to obtain the error description. A Warning tag may be set even if this routine is successful.

## CombineInfo

Combine information from more than one information hash into a single hash.

> Prototype | CombineInfo($;@)
> Inputs | 0) ExifTool object reference 1-N) List of info hash references
> Returns | Reference to combined information hash

Example:

>     $info = $exifTool->CombineInfo($info1, $info2, $info3);

If the Duplicates option is disabled and duplicate tags exist, the order of the hashes is significant. In this case, the value used is the first value found as the hashes are scanned in order of input. The Duplicates option is the only option that is in effect for this function.

## GetTagList

Get a sorted list of tags from the specified information hash or tag list.

> Prototype | GetTagList($;$$)
> Inputs | 0) ExifTool object reference 1) [optional] Reference to info hash or tag list 2) [optional] Sort order ('File', 'Input', 'Alpha' or 'Group#')
> Returns | List of tags in specified order

Example:

>     @tags = $exifTool->GetTagList($info, 'Group0');

If the information hash or tag list reference is not provided, then the list of found tags from the last call to ImageInfo, ExtractInfo or GetInfo is used instead, and the result is the same as if GetFoundTags was called. If sort order is not specified, the sort order is taken from the current options settings.

## GetFoundTags

Get list of found tags in specified sort order. The found tags are the tags for the information obtained from the most recent call to ImageInfo, ExtractInfo or GetInfo for this object.

> Prototype | GetFoundTags($;$)
> Inputs | 0) ExifTool object reference 1) [optional] Sort order ('File', 'Input', 'Alpha' or 'Group#')
> Returns | List of tags in specified order

Example:

>     my @tags = $exifTool->GetFoundTags('File');

## GetRequestedTags

Get list of requested tags. These are the tags that were specified in the arguments of the most recent call to ImageInfo, ExtractInfo or GetInfo, including tags specified via a tag list reference. They are returned in the same order that they were specified. Shortcut tags are expanded in the list.

> Prototype | GetRequestedTags($)
> Inputs | 0) ExifTool object reference
> Returns | List of requested tags (empty if no tags specifically requested)

Example:

>     my @requestedTags = $exifTool->GetRequestedTags();

## GetValue

Get the value of a specified tag. The returned value is either the human-readable (PrintConv) value, the converted machine-readable (ValueConv) value, or the original raw (Raw) value. If the value type is not specified, the PrintConv value is returned if the PrintConv option is set, otherwise the ValueConv value is returned. The PrintConv values are the same as the values returned by ImageInfo and GetInfo in the tag/value hash unless the PrintConv option is disabled.

Tags which represent lists of multiple values (as may happen with '`Keywords`' for example) are handled specially. In scalar context, the returned PrintConv value for these tags is either a comma-separated string of values or a list reference (depending on the List option setting), and the ValueConv value is always a list reference. But in list context, GetValue always returns the list itself.

> Prototype | GetValue($$;$)
> Inputs | 0) ExifTool object reference 1) Tag key 2) [optional] Value type, 'PrintConv', 'ValueConv', 'Both' or 'Raw' The default value type is 'PrintConv' if the PrintConv option is set, otherwise the default is 'ValueConv'. A value type of 'Both' returns both ValueConv and PrintConv values as a list.
> Returns | The value of the specified tag. If the tag represents a list of values and the List option is disabled then PrintConv returns a comma separated string of values, otherwise a reference to the list is returned in scalar context. The list itself is returned in list context. Values may also be scalar references to binary data. Note: It is possible for GetValue to return an undefined ValueConv or PrintConv value (or an empty list in list context) even if the tag exists, since it is possible for these conversions to yield undefined values.

Examples:

>     # PrintConv example
>     my $val = $exifTool->GetValue($tag);
>     if (ref $val eq 'SCALAR') {
>         print "$tag = (unprintable value)\n";
>     } else {
>         print "$tag = $val\n";
>     }

>     # ValueConv examples
>     my $val = $exifTool->GetValue($tag, 'ValueConv');
>     if (ref $val eq 'ARRAY') {
>         print "$tag is a list of values\n";
>     } elsif (ref $val eq 'SCALAR') {
>         print "$tag represents binary data\n";
>     } else {
>         print "$tag is a simple scalar\n";
>     }

>     my @keywords = $exifTool->GetValue('Keywords', 'ValueConv');

## SetNewValue

Set the new value for a tag. The routine may be called multiple times to set the values of many tags before using WriteInfo to write the new values to an image.

For list-type tags (like `Keywords`), either call repeatedly with the same tag name for each value, or call with a reference to the list of values.

> Prototype | SetNewValue($;$$$)
> Inputs | 0) ExifTool object reference 1) [optional] Tag key or tag name, or undefined to clear all new values. A tag name of '`*`' can be used when deleting tags to delete all tags, or all tags in a specified group. The tag name may be prefixed by group name, separated by a colon (ie. '`GROUP:TAG`'), which is equivalent to using a 'Group' option argument. 2) [optional] New value for tag. Undefined to delete tag from file. May be a scalar, scalar reference, or list reference to set a list of values. 3-N) [optional] SetNewValue options hash entries (see below).
> Returns | Scalar context: The number of tags set, and errors are printed to STDERR. List context: The number of tags set and the error string.

> SetNewValue Options
> Option | Description | Values | Default
> --- | --- | --- | ---
> Type | The type of value being set | PrintConv, ValueConv or Raw (default depends on PrintConv Option) | PrintConv or ValueConv
> AddValue | Add value to existing list rather than replacing the list | 0 or 1 | 0
> DelValue | Delete an existing tag if it has the specified value | 0 or 1 | 0
> Group | Specifies group name where tag should be written. If not specified, tag is written to hightest priority group as specified by SetNewGroups. Case is not significant | Any family 0 or 1 group name | undef
> NoShortcut | Disables default behaviour of looking up tag in shortcuts if not found otherwise. | 0 or 1 | 0
> Protected | Allow protected tags to be written | Bitmask of tag protection levels to write:
> 0x01 = | Write 'unsafe' tags (ie. tags not copied automatically via SetNewValuesFromFile)
> 0x02 = | Write 'protected' tags (internal use only)
> | 0
> Replace | Replace previous new value for this tag (ie. replace the value set in a previous call to SetNewValue) |
> 0 = | Don't replace
> 1 = | Replace with specified new value
> 2 = | Reset previous new value only
> | 0
> Shift | Shift the tag by the specified value. Currently only date/time tags can be shifted. Value is added if Shift is 1, or subtracted if Shift is -1. See Image::ExifTool::Shift.pl for details time shift formats. |
> undef = No shift
> 0 = | Shift if shiftable: 1 if AddValue set -1 if DelValue set
> 1 = | Positive shift
> -1 = | Negative shift
> | undef

Examples:

>     # set a new value for a tag (errors go to STDERR)
>     $success = $exifTool->SetNewValue($tag, $value);

>     # set a new value and capture any error message
>     ($success, $errStr) = $exifTool->SetNewValue($tag, $value);

>     # delete information for specified tag if it exists in image
>     # (also resets AddValue and DelValue options for this tag)
>     $exifTool->SetNewValue($tag);

>     # reset all values from previous calls to SetNewValue()
>     $exifTool->SetNewValue();

>     # delete a specific keyword
>     $exifTool->SetNewValue('Keywords', $word, DelValue => 1);

>     # write a list of keywords
>     $exifTool->SetNewValue('Keywords', ['word1','word2']);

>     # add a keyword without replacing existing keywords
>     $exifTool->SetNewValue(Keywords => $word, AddValue => 1);

>     # set a tag in a specific group
>     $exifTool->SetNewValue(Headline => $val, Group => 'XMP');
>     $exifTool->SetNewValue('XMP:Headline' => $val);  # equivalent

>     # shift original date/time back by 1 hour
>     $exifTool->SetNewValue(DateTimeOriginal => '1:00', Shift => -1);

## SetNewValuesFromFile

A very powerful routine that sets new values for tags from information found in a specified file.

> Prototype | SetNewValuesFromFile($$;@)
> Inputs | 0) ExifTool object reference 1) File name, file reference, or scalar reference 2-N) [optional] List of tag names to set. All writable tags are set if none are specified. The tag names are not case sensitive, and may be prefixed by an optional family 0 or 1 group name, separated by a colon (ie. '`exif:iso`'). A leading '`-`' indicates tags to be excluded (ie. '`-comment`'). An asterisk ('`*`') may be used for the tag name, and is useful when a group is specified to set all tags from a group (ie. '`XMP:*`'). A special feature allows tag names of the form '`SRCTAG>DSTTAG`' (or '`DSTTAG<SRCTAG`') to be specified to copy information to a tag with a different name or a specified group. Both '`SRCTAG`' and '`DSTTAG`' may use '`*`' and/or be prefixed by a group name (ie. '`modifyDate>fileModifyDate`' or '`*>xmp:*`'). Copied tags may also be added or deleted from a list with arguments of the form '`SRCTAG+>DSTTAG`' or '`SRCTAG->DSTTAG`'. Tags are evaluated in order, so exclusions apply only to tags included earlier in the list. An extension of this feature allows the tag value to be set from an expression containing tag names with leading '`$`' symbols (ie. '`Comment<Filename: $filename`'). Braces '`{}`' may be used around the tag name to separate it from subsequent text, and a '`$$`' is used to to represent a '`$`' symbol. (The behaviour for missing tags in expressions is defined by the MissingTagValue option.)
> Returns | A hash of information that was set successfully. May include Warning or Error entries if there were problems reading the input file.

By default, this routine will commute information between same-named tags in different groups, allowing information to be translated between images with different formats. This behaviour may be modified by specifying a group name for extracted tags (even if '`*`' is used as a group name), in which case the information is written to the original group, unless redirected to a different group. (For example, a tag name of '`*:*`' may be specified to copy all information while preserving the original groups.)

Examples:

>     # set new values from all information in a file...
>     my $info = $exifTool->SetNewValuesFromFile($srcFile);
>     # ...then write these values to another image
>     my $result = $exifTool->WriteInfo($file2, $outFile);

>     # set all new values, preserving original groups
>     $exifTool->SetNewValuesFromFile($srcFile, '*:*');

>     # set specific information
>     $exifTool->SetNewValuesFromFile($srcFile, $tag1, $tag2...);

>     # set new value from a different tag in specific group
>     $exifTool->SetNewValuesFromFile($src, 'IPTC:Keywords>XMP-dc:Subject');

>     # add all IPTC keywords to XMP subject list
>     $exifTool->SetNewValuesFromFile($src, 'IPTC:Keywords+>XMP-dc:Subject');

>     # set new value from an expression involving other tags
>     $exifTool->SetNewValuesFromFile($file,
>         'Comment<ISO=$ISO Aperture=$aperture Exposure=$shutterSpeed');

Notes:

The PrintConv option applies to this routine, but it normally should be left on to provide more reliable transfer of information between groups.

If a preview image exists, it is not copied. The preview image must be transferred separately if desired.

When simply copying all information between files of the same type, it is usually desirable to preserve the original groups by specifying '`*:*`' for the tags to set.

## GetNewValues

Get list of new Raw values for the specified tag. These are the values that will be written to file. Only tags which support a 'List' may return more than one value.

> Prototype | GetNewValues($$)
> Inputs | 0) ExifTool object reference 1) Tag key or tag name
> Returns | List of new Raw tag values. The list may be empty if the tag is being deleted (ie. if SetNewValue was called without a value).

Examples:

>     my $rawVal = $exifTool->GetNewValues($tag);

>     my @rawVals = $exifTool->GetNewValues($tag);

## CountNewValues

Return the total number of new values set.

> Prototype | CountNewValues($)
> Inputs | 0) ExifTool object reference
> Returns | In scalar context, returns the total number of tags with new values set. In list context, also returns the number of "pseudo" tag values which have been set. "Pseudo" tags are tags like FileName and FileModifyDate which are not contained within the file and can be changed without rewriting the file.

Examples:

>     my $numSet = $exifTool->CountNewValues();
>     my ($numSet, $numPseudo) = $exifTool->CountNewValues();

## SaveNewValues

Save state of new values to be later restored by RestoreNewValues.

> Prototype | SaveNewValues($)
> Inputs | 0) ExifTool object reference

Example:

>     $exifTool->SaveNewValues();         # save state of new values
>     $exifTool->SetNewValue(ISO => 100); # set new value for ISO
>     $exifTool->WriteInfo($src, $dst1);  # write ISO plus any previous new values
>     $exifTool->RestoreNewValues();      # restore previous new values
>     $exifTool->WriteInfo($src, $dst2);  # write previous new values only

## RestoreNewValues

Restore new values to the settings that existed when SaveNewValues was last called. May be called repeatedly after a single call to SaveNewValues. See SaveNewValues above for an example.

> Prototype | RestoreNewValues($)
> Inputs | 0) ExifTool object reference

## SetFileModifyDate

Set the file modification time from the new value of the FileModifyDate tag.

> Prototype | SetFileModifyDate($$;$)
> Inputs | 0) ExifTool object reference 1) File name 2) [optional] Base time if applying shift (in days before $^T)
> Returns | 1 if the time was changed, 0 if nothing was done, or -1 if there was an error setting the time.

Example:

>     my $result = $exifTool->SetFileModifyDate($file);

## SetFileName

Set the file name and directory. If not specified, the new file name is derived from the new values of the FileName and Directory tags. If the FileName tag contains a '`/`', then the file is renamed into a new directory. If FileName ends with '`/`', then it is taken as a directory name and the file is moved into the new directory. The new value for the Directory tag takes precedence over any directory specified in FileName.

> Prototype | SetFileName($$;$)
> Inputs | 0) ExifTool object reference 1) Current file name 2) [optional] New file name
> Returns | 1 if the file name or directory was changed, 0 if nothing was done, or -1 if there was an error renaming the file.

Example:

>     my $result = $exifTool->SetFileName($file);
>     my $result = $exifTool->SetFileName($file, $newName);

Notes:

Will not overwrite existing files. New directories are created as necessary.

## SetNewGroups

Set the order of the preferred groups when adding new information. In subsequent calls to SetNewValue, new information will be created in the first valid group of this list. This has an impact only if the group is not specified when calling SetNewValue, and if the tag name exists in more than one group. The default order is EXIF, IPTC, XMP then MakerNotes. Any family 0 group name may be used. Case is not significant.

> Prototype | SetNewGroups($;@)
> Inputs | 0) ExifTool object reference 1-N) Groups in order of priority. If no groups are specified, the priorities are reset to the defaults.

Examples:

>     $exifTool->SetNewGroups('XMP','EXIF','IPTC');

## GetNewGroups

Get current group priority list.

> Prototype | GetNewGroups($)
> Inputs | 0) ExifTool object reference
> Returns | List of group names in order of write priority. Highest priority first.

Examples:

>     @groups = $exifTool->GetNewGroups();

## GetTagID

Get the ID for the specified tag. The ID is the IFD tag number in EXIF information, the property name in XMP information, or the data offset in a binary data block. For some tags, such as Composite tags where there is no ID, an empty string is returned.

> Prototype | GetTagID($$)
> Inputs | 0) ExifTool object reference 1) Tag key
> Returns | Tag ID or '' of there is no ID for this tag

Example:

>     my $id = $exifTool->GetTagID($tag);

## GetDescription

Get description for specified tag. This function will always return a defined value. In the case where the description doesn't exist, the tag name is returned.

> Prototype | GetDescription($$)
> Inputs | 0) ExifTool object reference 1) Tag key
> Returns | Tag description

## GetGroup

Get group name for specified tag.

> Prototype | GetGroup($$;$)
> Inputs | 0) ExifTool object reference 1) Tag key 2) [optional] Group family number
> Returns | Group name (or 'Other' if tag has no group). If no group family is specified, returns the name of group in family 0 when called in scalar context, or the names of groups for all families in list context. See GetAllGroups for a list of group names.

Example:

>     my $group = $exifTool->GetGroup($tag, 0);

## GetGroups

Get list of group names for all tags in specified information hash.

> Prototype | GetGroups($;$$)
> Inputs | 0) ExifTool object reference 1) [optional] Information hash reference (default is all extracted info) 2) [optional] Group family number (default 0)
> Returns | List of group names in alphabetical order. If information hash is not specified, the group names are returned for all extracted information. See GetAllGroups for a complete list of group names.

Examples:

>     my @groups = $exifTool->GetGroups($info, $family);

> Example of one way to print information organized by group

>     my $exifTool = new Image::ExifTool;
>     $exifTool->ExtractInfo('t/images/ExifTool.jpg');

>     my $family = 1;
>     my @groups = $exifTool->GetGroups($family);
>     my $group;
>     foreach $group (@groups) {
>         print "---- $group ----\n";
>         my $info = $exifTool->GetInfo({"Group$family" => $group});
>         foreach ($exifTool->GetTagList($info)) {
>             print "$_ : $$info{$_}\n";
>         }
>     }

## BuildCompositeTags

Builds composite tags from required tags. The composite tags are convenience tags which are derived from the values of other tags. This routine is called automatically by ImageInfo if the Composite option is set.

> Prototype | BuildCompositeTags($)
> Inputs | 0) ExifTool object reference
> Returns | (none)

Notes:

1. Tag values are calculated in alphabetical order unless a tag Require's or Desire's another composite tag, in which case the calculation is deferred until after the other tag is calculated.
2. Composite tags may need to read data from the image for their value to be determined, so for these BuildCompositeTags must be called while the image is available. This is only a problem if ImageInfo is called with a filename (as opposed to a file reference or scalar reference) since in this case the file is closed before ImageInfo returns. However if you enable the Composite option, BuildCompositeTags is called from within ImageInfo before the file is closed.

The following functions access only static data and are not called with an ExifTool object

The names of all the following functions, plus ImageInfo, may be imported into the current namespace with the "Public" tag. When this is done, the functions can be accessed without the need to prefix the function name with "`Image::ExifTool::`". For example:

>     use Image::ExifTool ':Public';
>     $tagName = GetTagName($tag);

## GetTagName

Get name of tag from tag identifier. This is a convenience function that strips the embedded instance number, if it exists, from the tag key.

> Prototype | GetTagName($)
> Inputs | 0) Tag key
> Returns | Tag name

Example:

>     $tagName = Image::ExifTool::GetTagName($tag);

## GetShortcuts

Get list of tag shortcut names.

> Prototype | GetShortcuts()
> Inputs | (none)
> Returns | List of shortcuts

## GetAllTags

Get list of all available tag names.

> Prototype | GetAllTags(;$)
> Inputs | 0) [optional] Group name
> Returns | A list of all available tags in alphabetical order, or all tags in specified group. The group name is case insensitive, and any group in any family may be used except for EXIF family 1 groups (ie. the specific IFD).

## GetWritableTags

Get list of all writable tag names.

> Prototype | GetWritableTags(;$)
> Inputs | 0) [optional] Group name
> Returns | A list of all writable tags in alphabetical order. These are the tags for which values may be set through SetNewValue. If a group name is given, returns only writable tags in specified group. The group name is case insensitive, and any group in any family may be used except for EXIF family 1 groups (ie. the specific IFD).

## GetAllGroups

Get list of all group names in specified family.

> Prototype | GetAllGroups($)
> Inputs | 0) Group family number (0-2)
> Returns | A list of all groups in the specified family in alphabetical order

Three families of groups are currently defined: 0, 1 and 2. Families 0 and 1 are based on the file structure, and family 2 classifies information based on the logical category to which the information refers.

Families 0 and 1 are similar except that family 1 is more specific, and sub-divides the EXIF, MakerNotes, XMP and ICC_Profile groups to give more detail about the specific location where the information was found. The EXIF group is split up based on the specific IFD (Image File Directory), the MakerNotes group is divided into groups for each manufacturer, and the XMP group is separated based on the XMP namespace prefix. Note that only common XMP namespaces are listed below but additional namespaces may be present in some XMP data. Also note that the '`XMP-xmp`...' group names may appear in the older form '`XMP-xap`...' since these names evolved as the XMP standard was developed. The ICC_Profile group is broken down to give information about the specific ICC_Profile tag from which multiple values were extracted. As well, information extracted from the ICC_Profile header is separated into the ICC-header group.

Here is a complete list of groups for each family:

> Family | Group Names
> --- | ---
> 0 (Information Type) | AFCP, AIFF, APE, APP12, APP13, APP14, APP15, APP5, APP6, APP8, ASF, BMP, CanonVRD, Composite, DICOM, DNG, Ducky, EXIF, ExifTool, FLAC, File, Flash, FlashPix, FotoStation, GeoTiff, HTML, ICC_Profile, ID3, IPTC, JFIF, JPEG, Jpeg2000, Leaf, MIE, MIFF, MNG, MPC, MPEG, MakerNotes, Meta, PDF, PICT, PNG, PhotoMechanic, Photoshop, PostScript, PrintIM, QuickTime, RAF, RIFF, Real, SigmaRaw, Vorbis, XMP
> 1 (Specific Location) | AFCP, AIFF, APE, ASF, Adobe, AdobeCM, BMP, Canon, CanonCustom, CanonRaw, CanonVRD, Casio, Composite, DICOM, DNG, Ducky, EPPIM, ExifIFD, ExifTool, FLAC, File, Flash, FlashPix, FotoStation, FujiFilm, GPS, GeoTiff, GlobParamIFD, GraphConv, HP, HTML, HTML-dc, HTML-ncc, HTML-prod, HTML-vw96, HTTP-equiv, ICC-chrm, ICC-clrt, ICC-header, ICC-meas, ICC-view, ICC_Profile, ID3, ID3v1, ID3v2_2, ID3v2_3, ID3v2_4, IFD0, IFD1, IPTC, InteropIFD, JFIF, JPEG, JVC, Jpeg2000, Kodak, KodakBordersIFD, KodakEffectsIFD, KyoceraRaw, Leaf, LeafSubIFD, MAC, MIE-Audio, MIE-Camera, MIE-Doc, MIE-Extender, MIE-Flash, MIE-GPS, MIE-Geo, MIE-Image, MIE-Lens, MIE-Main, MIE-MakerNotes, MIE-Meta, MIE-Orient, MIE-Preview, MIE-Thumbnail, MIE-UTM, MIE-Unknown, MIE-Video, MIFF, MNG, MPC, MPEG, MakerNotes, MakerUnknown, MetaIFD, Minolta, MinoltaRaw, Nikon, NikonCapture, NikonPreview, NikonScan, Olympus, PDF, PICT, PNG, Panasonic, Pentax, PhotoMechanic, Photoshop, PictureInfo, PostScript, PrintIM, QuickTime, RAF, RAF2, RIFF, RMETA, Real, Real-CONT, Real-MDPR, Real-PROP, Real-RA3, Real-RA4, Real-RA5, Real-RJMD, Ricoh, SPIFF, SR2, SRF#, Sanyo, Sigma, SigmaRaw, Sony, SubIFD, Track#, Vorbis, XMP, XMP-DICOM, XMP-PixelLive, XMP-aux, XMP-cc, XMP-crs, XMP-dc, XMP-dex, XMP-exif, XMP-iptcCore, XMP-lr, XMP-mediapro, XMP-microsoft, XMP-pdf, XMP-photomech, XMP-photoshop, XMP-tiff, XMP-xmp, XMP-xmpBJ, XMP-xmpDM, XMP-xmpMM, XMP-xmpPLUS, XMP-xmpRights, XMP-xmpTPg
> 2 (Category) | Audio, Author, Camera, Document, ExifTool, Image, Location, Other, Printing, Time, Unknown, Video

Example:

>     @groupList = Image::ExifTool::GetAllGroups($family);

## GetDeleteGroups

Get list of all deletable group names.

> Prototype | GetDelGroups()
> Inputs | None
> Returns | A list of deletable group names in alphabetical order.

Below is a current list of deletable group names. All names in this list are either family 0 or family 1 group names, with the exception of '`Trailer`' which allows all trailers in JPEG and TIFF-format images to be deleted at once, including unknown trailers. To schedule a group for deletion, call SetNewValue with an undefined value and a tag name like '`Trailer:*`'.

> AFCP, CIFF, CanonVRD, EXIF, ExifIFD, Ducky, File, FlashPix, FotoStation, GlobParamIFD, GPS, IFD0, IFD1, InteropIFD, ICC_Profile, IPTC, JFIF, MakerNotes, Meta, MetaIFD, MIE, PhotoMechanic, Photoshop, PNG, PrintIM, RMETA, SubIFD, Trailer, XMP

Example:

>     my @delGroups = Image::ExifTool::GetDelGroups();

## GetFileType

Get type of file given file name.

> Prototype | GetFileType(;$$)
> Inputs | 0) [optional] File name (or just an extension) 1) [optional] Flag to return a description instead of a type
> Returns | A string, based on the file extension, which represents the type of file (or a description of the file type). Returns undefined if the file type isn't supported by ExifTool. In array context, may return more than one file type if the file may be different formats. With no arguments, returns a list of extensions for all recognized file types.

Example:

>     my $type = Image::ExifTool::GetFileType($filename);
>     my $desc = Image::ExifTool::GetFileType($filename, 1);

## CanWrite

Can the specified file or file type be written?

> Prototype | CanWrite($)
> Inputs | 0) File name, file extension, or file type
> Returns | True if the file type can be written (edited).

Example:

>     my $writable = Image::ExifTool::CanWrite($filename);

## CanCreate

Can the specified file or file type be created?

> Prototype | CanCreate($)
> Inputs | 0) File name, file extension, or file type
> Returns | True if the file type can be created from scratch. Currently, this can only be done with XMP files.

Example:

>     my $creatable = Image::ExifTool::CanCreate($filename);

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