#------------------------------------------------------------------------------
# File:         ExifTool.pod - Documentation for File::ExifTool
#
# Description:  Read and write meta information
#
# URL:          http://owl.phy.queensu.ca/~phil/exiftool/
#
# Legal:        Copyright (c) 2003-2010, Phil Harvey (phil at owl.phy.queensu.ca)
#               This library is free software; you can redistribute it and/or
#               modify it under the same terms as Perl itself.
#------------------------------------------------------------------------------

=head1 NAME

Image::ExifTool - Read and write meta information

=head1 SYNOPSIS

  use Image::ExifTool qw(:Public);

  # ---- Simple procedural usage ----

  # Get hash of meta information tag names/values from an image
  $info = ImageInfo('a.jpg');

  # ---- Object-oriented usage ----

  # Create a new Image::ExifTool object
  $exifTool = new Image::ExifTool;

  # Extract meta information from an image
  $exifTool->ExtractInfo($file, \%options);

  # Get list of tags in the order they were found in the file
  @tagList = $exifTool->GetFoundTags('File');

  # Get the value of a specified tag
  $value = $exifTool->GetValue($tag, $type);

  # Get a tag description
  $description = $exifTool->GetDescription($tag);

  # Get the group name associated with this tag
  $group = $exifTool->GetGroup($tag, $family);

  # Set a new value for a tag
  $exifTool->SetNewValue($tag, $newValue);

  # Write new meta information to a file
  $success = $exifTool->WriteInfo($srcfile, $dstfile);

  # ...plus a host of other useful methods...

=head1 DESCRIPTION

ExifTool provides an extensible set of perl modules to read and write meta
information in a wide variety of files, including the maker note information
of many digital cameras by various manufacturers such as Canon, Casio,
FujiFilm, HP, JVC/Victor, Kodak, Leaf, Minolta/Konica-Minolta, Nikon,
Olympus/Epson, Panasonic/Leica, Pentax/Asahi, Ricoh, Samsung, Sanyo,
Sigma/Foveon and Sony.

Below is a list of file types and meta information formats currently
supported by ExifTool (r = read, w = write, c = create):

  File Types
  ------------+-------------+-------------+-------------+------------
  3FR   r     | DVB   r     | M2TS  r     | PAGES r     | RW2   r/w  
  3G2   r     | DYLIB r     | M4A/V r     | PBM   r/w   | RWL   r/w
  3GP   r     | EIP   r     | MEF   r/w   | PDF   r/w   | RWZ   r
  ACR   r     | EPS   r/w   | MIE   r/w/c | PEF   r/w   | RM    r
  AFM   r     | ERF   r/w   | MIFF  r     | PFA   r     | SO    r
  AI    r/w   | EXE   r     | MKA   r     | PFB   r     | SR2   r/w
  AIFF  r     | EXIF  r/w/c | MKS   r     | PFM   r     | SRF   r
  APE   r     | F4A/V r     | MKV   r     | PGM   r/w   | SRW   r/w
  ARW   r/w   | FLA   r     | MNG   r/w   | PICT  r     | SVG   r
  ASF   r     | FLAC  r     | MOS   r/w   | PMP   r     | SWF   r
  AVI   r     | FLV   r     | MOV   r     | PNG   r/w   | THM   r/w
  BMP   r     | FPX   r     | MP3   r     | PPM   r/w   | TIFF  r/w
  BTF   r     | GIF   r/w   | MP4   r     | PPT   r     | TTC   r
  COS   r     | GZ    r     | MPC   r     | PPTX  r     | TTF   r
  CR2   r/w   | HDP   r/w   | MPG   r     | PS    r/w   | VRD   r/w/c
  CRW   r/w   | HTML  r     | MPO   r/w   | PSB   r/w   | WAV   r
  CS1   r/w   | ICC   r/w/c | MQV   r     | PSD   r/w   | WDP   r/w
  DCM   r     | IIQ   r     | MRW   r/w   | PSP   r     | WEBP  r
  DCP   r/w   | IND   r/w   | NEF   r/w   | QTIF  r     | WEBM  r
  DCR   r     | ITC   r     | NRW   r/w   | RA    r     | WMA   r
  DFONT r     | JNG   r/w   | NUMBERS r   | RAF   r/w   | WMV   r
  DIVX  r     | JP2   r/w   | ODP   r     | RAM   r     | X3F   r/w
  DJVU  r     | JPEG  r/w   | ODS   r     | RAR   r     | XCF   r
  DLL   r     | K25   r     | ODT   r     | RAW   r/w   | XLS   r
  DNG   r/w   | KDC   r     | OGG   r     | RIFF  r     | XLSX  r
  DOC   r     | KEY   r     | ORF   r/w   | RSRC  r     | XMP   r/w/c
  DOCX  r     | LNK   r     | OTF   r     | RTF   r     | ZIP   r

  Meta Information
  ----------------------+----------------------+---------------------
  EXIF           r/w/c  |  Kodak Meta     r/w  |  Picture Info   r
  GPS            r/w/c  |  FotoStation    r/w  |  Adobe APP14    r
  IPTC           r/w/c  |  PhotoMechanic  r/w  |  MPF            r
  XMP            r/w/c  |  JPEG 2000      r    |  Stim           r
  MakerNotes     r/w/c  |  DICOM          r    |  APE            r
  Photoshop IRB  r/w/c  |  Flash          r    |  Vorbis         r
  ICC Profile    r/w/c  |  FlashPix       r    |  SPIFF          r
  MIE            r/w/c  |  QuickTime      r    |  DjVu           r
  JFIF           r/w/c  |  Matroska       r    |  M2TS           r
  Ducky APP12    r/w/c  |  GeoTIFF        r    |  PE/COFF        r
  PDF            r/w/c  |  PrintIM        r    |  AVCHD          r
  CIFF           r/w    |  ID3            r    |  ZIP            r
  AFCP           r/w    |  Ricoh RMETA    r    |  (and more)

=head1 CONFIGURATION

User-defined tags can be added via the ExifTool configuration file, or by
defining the %Image::ExifTool::UserDefined hash before calling any ExifTool
methods.  See "ExifTool_config" in the ExifTool distribution for more
details.

By default ExifTool looks for a configuration file named ".ExifTool_config"
first in your home directory, then in the directory of the application
script, but a different file may be specified by setting the ExifTool
C<configFile> variable before using Image::ExifTool.  For example:

    BEGIN { $Image::ExifTool::configFile = '/Users/phil/myconfig.cfg' }
    use Image::ExifTool;

or the configuration feature may be disabled by setting C<configFile> to an
empty string:

    BEGIN { $Image::ExifTool::configFile = '' }
    use Image::ExifTool;

=head1 EXPORTS

Exports nothing by default, but L</ImageInfo> and all static methods may be
exported with the C<:Public> export list.

=head1 METHODS

All ExifTool features are accessed through the methods of the public
interface listed below.  Other Image::ExifTool methods and modules should
not be accessed directly because their interface may change with future
versions.

None of these methods should ever die or issue warnings to STDERR if called
with the proper arguments (with the exception of L</SetNewValue> which
returns an error string when called in list context, or sends the error to
STDERR otherwise).  Error and warning messages that occur during processing
are stored in the values of the Error and Warning tags, and are accessible
via the L</GetValue> method.

=head2 new

Creates a new ExifTool object.

    $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, @_);
    }

=head2 ImageInfo

Read image file and return meta information.  This is the one step function
for retrieving meta information from an image.  Internally, L</ImageInfo>
calls L</ExtractInfo> to extract the information, L</GetInfo> to generate
the information hash, and L</GetTagList> for the returned tag list.

    # return meta information for 2 tags only (procedural)
    $info = ImageInfo($filename, $tag1, $tag2);

    # return information about an open image file (object-oriented)
    $info = $exifTool->ImageInfo(\*FILE);

    # return information from image data in memory for specified tags
    %options = (PrintConv => 0);
    @tagList = qw(filename imagesize xmp:creator exif:* -ifd1:*);
    $info = ImageInfo(\$imageData, \@tagList, \%options);

    # extract information from an embedded thumbnail image
    $info = ImageInfo('image.jpg', 'thumbnailimage');
    $thumbInfo = ImageInfo($$info{ThumbnailImage});

=over 4

=item Inputs:

L</ImageInfo> is very flexible about the input arguments, 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 an explanation of how the L</ImageInfo> function arguments are
interpreted:

=over 4

=item ExifTool ref

L</ImageInfo> may be called with an ExifTool object if desired.  The
advantage of using the object-oriented form is that the options may be set
before calling L</ImageInfo>, and the object may be used afterward to access
member functions.  Must be the first argument if used.

=item 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.  All tags are returned if no tags are specified.

Tag names are case-insensitive and may be prefixed by optional group names
separated by colons.  A group name may begin with a family number (ie.
'1IPTC:Keywords'), to restrict matches to a specific family.  In the tag
name, a '?' matches any single character and a '*' matches zero or more
characters.  Thus 'GROUP:*' represents all tags in a specific group. 
Wildcards may not be used in group names, with the exception that a group
name of '*' may be used to extract all available instances of a tag
regardless of the L</Duplicates> setting (ie. '*:WhiteBalance').  Multiple
groups may be specified (ie. 'EXIF:Time:*' extracts all EXIF Time tags). And
finally, a leading '-' indicates a tag to be excluded (ie. '-IFD1:*'), or a
trailing '#' causes the ValueConv value to be returned for this tag.

Note that keys in the returned information hash and elements of the returned
tag list are not necessarily the same as these tag names because 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 L<Image::ExifTool::TagNames|Image::ExifTool::TagNames> for a complete
list of ExifTool tag names.

=item 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, FileModifyDate and
FilePermissions 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.  May be either a standard filehandle, or a
reference to a L<File::RandomAccess|File::RandomAccess> object.  Note that
the file remains open and must be closed by the caller after L</ImageInfo>
returns.

[Advanced:  To allow a non-rewindable stream (ie. a network socket) to be
re-read after processing with ExifTool, first wrap the file reference in a
L<File::RandomAccess|File::RandomAccess> object, then pass this object to
L</ImageInfo>.  The L<File::RandomAccess|File::RandomAccess> object will
buffer the file if necessary, and may be used to re-read the file after
L</ImageInfo> returns.]

=item SCALAR ref

A reference to image data in memory.

=item ARRAY ref

Reference to a list of tag names.  On entry, any elements in the list are
added to the list of requested tags.  Tags with names beginning with '-' are
excluded.  On return, this list is updated to contain an ordered list of tag
keys for all extracted tags.

=item HASH ref

Reference to a hash containing the options settings.  See L</Options>
documentation below for a list of available options.  Options specified
as arguments to L</ImageInfo> take precedence over L</Options> settings.

=back

=item Return Values:

L</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 L</GetTagName [static]> 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.
Here is a simple example to print out the information returned by
L</ImageInfo>:

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

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 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".  The value may also be a hash reference if the
Struct option is enabled.

The code below gives an example of how to handle these return values, as
well as illustrating the use of other ExifTool functions:

    use Image::ExifTool;
    my $exifTool = new Image::ExifTool;
    $exifTool->Options(Unknown => 1);
    my $info = $exifTool->ImageInfo('a.jpg');
    my $group = '';
    my $tag;
    foreach $tag ($exifTool->GetFoundTags('Group0')) {
        if ($group ne $exifTool->GetGroup($tag)) {
            $group = $exifTool->GetGroup($tag);
            print "---- $group ----\n";
        }
        my $val = $info->{$tag};
        if (ref $val eq 'SCALAR') {
            if ($$val =~ /^Binary data/) {
                $val = "($$val)";
            } else {
                my $len = length($$val);
                $val = "(Binary data $len bytes)";
            }
        }
        printf("%-32s : %s\n", $exifTool->GetDescription($tag), $val);
    }

=item Notes:

ExifTool returns all values as byte strings of encoded characters.  Perl
wide characters are not used.  See L</CHARACTER ENCODINGS> for details about
the encodings.

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 processed.

    Warning - A warning message if problems were encountered while
              processing the image.

=back

=head2 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 some functions.

The initial default options are obtained from values in the
%Image::ExifTool::UserDefined::Options hash if it exists.  See the
.ExifTool_config file in the full ExifTool distribution for details.

    # exclude the 'OwnerName' tag from returned information
    $exifTool->Options(Exclude => 'OwnerName');

    # only get information in EXIF or MakerNotes groups
    $exifTool->Options(Group0 => ['EXIF', 'MakerNotes']);

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

    # sort by groups in family 2, and extract unknown tags
    $exifTool->Options(Sort => 'Group2', Unknown => 1);

    # reset DateFormat option
    $exifTool->Options(DateFormat => undef);

    # do not extract duplicate tag names
    $oldSetting = $exifTool->Options(Duplicates => 0);

    # get current Verbose setting
    $isVerbose = $exifTool->Options('Verbose');

=over 4

=item Inputs:

0) ExifTool object reference.

1) Option parameter name.

2) [optional] Option parameter value (may be undef to clear option).

3-N) [optional] Additional parameter/value pairs.

=item Option Parameters:

=over 4

=item 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.
Default is 0.

=item ByteOrder

The byte order for newly created EXIF segments when writing.  Note that if
EXIF information already exists, the existing order is maintained.  Valid
values are 'MM', 'II' and undef.  If ByteOrder is not defined (the default),
then the maker note byte order 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.

=item Charset

Character set for encoding character strings passed to/from ExifTool with
code points above U+007F.  Default is UTF8.  Valid values are listed below,
case is not significant:

  Value        Alias(es)        Description
  -----------  ---------------  ----------------------------------
  UTF8         cp65001, UTF-8   UTF-8 characters
  Latin        cp1252, Latin1   Windows Latin1 (West European)
  Latin2       cp1250           Windows Latin2 (Central European)
  Cyrillic     cp1251, Russian  Windows Cyrillic
  Greek        cp1253           Windows Greek
  Turkish      cp1254           Windows Turkish
  Hebrew       cp1255           Windows Hebrew
  Arabic       cp1256           Windows Arabic
  Baltic       cp1257           Windows Baltic
  Vietnam      cp1258           Windows Vietnamese
  Thai         cp874            Windows Thai
  MacRoman     cp10000, Roman   Macintosh Roman
  MacLatin2    cp10029          Macintosh Latin2 (Central Europe)
  MacCyrillic  cp10007          Macintosh Cyrillic
  MacGreek     cp10006          Macintosh Greek
  MacTurkish   cp10081          Macintosh Turkish
  MacRomanian  cp10010          Macintosh Romanian
  MacIceland   cp10079          Macintosh Icelandic
  MacCroatian  cp10082          Macintosh Croatian

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.

=item CharsetID3

Character encoding to assume for ID3v1 strings.  By the specification ID3v1
strings should be encoded in ISO 8859-1 (essentially Latin), but some
applications may use local encoding instead.  Default is Latin.

=item CharsetIPTC

Fallback IPTC character set to assume if IPTC information contains no
CodedCharacterSet tag.  Possible values are the same as the L</Charset>
option.  Default is Latin.

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.

=item CharsetPhotoshop

Character encoding to assume for Photoshop IRB resource names.  Default is
Latin.

=item Compact

Flag to write compact output.  Default is 0.  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.

=item Composite

Flag to calculate Composite tags automatically.  Default is 1.

=item Compress

Flag to write new values in compressed format if possible.  Has no effect
unless Compress::Zlib is installed.  Default is 0.

=item CoordFormat

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.  For example, the following table gives the
output for the same coordinate using various formats:

      CoordFormat        Example Output
  -------------------  ------------------
  q{%d deg %d' %.2f"}  54 deg 59' 22.80"  (default for reading)
  q{%d %d %.8f}        54 59 22.80000000  (default for copying)
  q{%d deg %.4f min}   54 deg 59.3800 min
  q{%.6f degrees}      54.989667 degrees

Note:  To avoid loss of precision, the default coordinate format is
different when copying tags with L</SetNewValuesFromFile>.

=item DateFormat

Format for printing date/time values.  See C<strftime> in the L<POSIX>
package for details about the format string.  The default is similar to a
format of "%Y:%m:%d %H:%M:%S".  If date can not be converted, value is left
unchanged unless the StrictDate option is set.  Timezones are ignored.

=item Duplicates

Flag to return values from tags with duplicate names when extracting
information.  Default is 1.

=item Escape

Escape special characters in extracted values for HTML or XML.  Also
unescapes HTML or XML character entities in input values passed to
L</SetNewValue>.  Valid settings are 'HTML', 'XML' or undef.  Default is
undef.

=item Exclude

Exclude specified tags from tags extracted from an image.  The option value
is either a tag name or reference to a list of tag names to exclude.  The
case of tag names is not significant.  This option is ignored for
specifically requested tags.  Tags may also be excluded by preceeding their
name with a '-' in the arguments to L</ImageInfo>.

=item ExtractEmbedded

Flag to extract information from embedded documents in PostScript files and
the AIPrivateData stream in PDF files, and embedded MPF images in JPEG and
MPO files.  Default is 0.

=item FastScan

Flag to increase speed of extracting information from JPEG images.  With
this option set to 1, ExifTool will not scan to the end of a JPEG image to
check for an AFCP, CanonVRD, FotoStation, PhotoMechanic, MIE or PreviewImage
trailer.  This also stops the parsing after the first comment in GIF images,
and at the audio/video data with RIFF-format files (AVI, WAV, etc), so any
trailing metadata (ie. XMP written by some utilities) may be missed.  When
combined with the ScanForXMP option, prevents scanning for XMP in recognized
file types.  With a value of 2, ExifTool will also avoid extracting any EXIF
MakerNote information.  Default is 0.

=item FixBase

Fix maker notes base offset.  A common problem with image editing software
is that offsets in the maker notes are not adjusted properly when the file
is modified.  This may cause the wrong values to be extracted for some maker
note entries when reading the edited file.  FixBase specifies an integer
value to be added to the maker notes base offset.  It may also be set to the
empty string ('') for ExifTool will take its best guess at the correct base,
or undef (the default) for no base adjustment.

=item GeoMaxIntSecs

Maximum interpolation time in seconds for geotagging.  Geotagging fails if
the Geotime value lies between two fixes in the same track which are
separated by a number of seconds greater than this.  Default is 1800.

=item GeoMaxExtSecs

Maximum extrapolation time in seconds for geotagging.  Geotagging fails if
the Geotime value lies outside a GPS track by a number of seconds greater
than this.  Default is 1800.

=item GeoMaxHDOP

Maximum Horizontal (2D) Dilution Of Precision for geotagging.  GPS fixes are
ignored if the HDOP is greater than this.  Default is undef.

=item GeoMaxPDOP

Maximum Position (3D) Dilution Of Precision for geotagging.  GPS fixes are
ignored if the PDOP is greater than this.  Default is undef.

=item GeoMinSats

Minimum number of satellites for geotagging.  GPS fixes are ignored if the
number of acquired satellites is less than this.  Default is undef.

=item Group#

Extract tags only for specified groups in family # (Group0 assumed if #
not given).  The option value may be a single group name or a reference
to a list of groups.  Case is significant in group names.  Specify a group
to be excluded by preceding group name with a '-'.  See L</GetGroup> for a
description of group families, and L</GetAllGroups [static]> for lists of
group names.

=item HtmlDump

Dump information in hex to dynamic HTML web page.  The value may be 0-3 for
increasingly larger limits on the maximum block size.  Default is 0.  Output
goes to the file specified by the TextOut option (\*STDOUT by default).

=item HtmlDumpBase

Specifies base for HTML dump offsets.  If not defined, the EXIF/TIFF base
offset is used.  Set to 0 for absolute offsets.  Default is undef.

=item 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 by ignoring some
minor warnings the behaviour of ExifTool may be changed to allow some
questionable operations to proceed (such as extracting thumbnail and preview
images even if they don't have a recognizable header).  Minor
errors/warnings are denoted by '[minor]' at the start of the message.

=item Lang

Localized language for exiftool tag descriptions, etc.  Available languages
are given by the Image::ExifTool::Lang module names (ie. 'fr').  If the
specified language isn't available, the option is not changed.  May be set
to undef to select the built-in default language.  Default is 'en'.

=item LargeFileSupport

Flag to indicate that 64-bit file offsets are supported on this system.
Default is 0.

=item List

Flag to extract lists of PrintConv values into arrays instead of joining
them into a string of values.  The L</ListSep> option specifies the
separator used when combining values.  Default is 0.

=item ListSep

Separator string used to join lists of PrintConv values when L</List> option
is not set.  Default is ', '.

=item ListSplit

Regular expression used to split values of list-type tags into individual
items when writing.  (ie. use ',\\s*' to split a comma-separated list.) 
Default is undef.

=item 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.  Possible values
are:

  0 - Do not extract writable subdirectories [default]
  1 - Extract and rebuild maker notes into self-contained block
  2 - Extract without rebuilding maker notes

=item MissingTagValue

Value for missing tags in expressions evaluated by L</SetNewValuesFromFile>.
If not set, a minor error is issued for missing values, or the value is set
to '' if L</IgnoreMinorErrors> is set.  Default is undef.

=item Password

Password for processing password-protected PDF documents.  Ignored if a
password is not required.  Character encoding of the password is determined
by the value of the Charset option at processing time.  Default is undef.

=item PrintConv

Flag to enable automatic print conversion.  Also enables inverse
print conversion for writing.  Default is 1.

=item 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.  Default is 0.

=item Sort

Specifies order to sort tags in returned list:

  Alpha  - Sort alphabetically
  File   - Sort in order that tags were found in the file
  Group# - Sort by tag group, where # is zero or more family
           numbers separated by colons. If # is not specified,
           Group0 is assumed.  See GetGroup for a description
           of group families.
  Input  - Sort in same order as input tag arguments (default)

=item StrictDate

Flag to return undefined value for any date which can't be converted when
the DateFormat option is used.  Default is 0.

=item Struct

Flag to return XMP structures as hash references instead of flattening into
individual tags.  Default is 0.  Currently, the struct feature applies only
when reading (so L</SetNewValue> can not be called with a hash reference
when writing).

=item TextOut

Output file reference for Verbose and HtmlDump options.  Default is
\*STDOUT.

=item Unknown

Flag to get the values of unknown tags.  If set to 1, unknown tags are
extracted from EXIF (or other tagged-format) directories.  If set to 2,
unknown tags are also extracted from binary data blocks.  Default is 0.

=item Verbose

Print verbose messages to file specified by TextOut option.  Value may be
from 0 to 5 for increasingly verbose messages.  Default is 0.  With the
verbose option set, messages are printed to the console as the file is
parsed.  Level 1 prints the tag names and raw values.  Level 2 adds more
details about the tags.  Level 3 adds a hex dump of the tag data, but with
limits on the number of bytes dumped.  Levels 4 and 5 remove the dump limit
on tag values and JPEG segment data respectively.

=back

=item Return Values:

The original value of the last specified parameter.

=back

=head2 ClearOptions

Reset all options to their default values.  Loads user-defined default
option values from the %Image::ExifTool::UserDefined::Options hash in the
.ExifTool_config file if it exists.

    $exifTool->ClearOptions();

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Values:

(none)

=back

=head2 ExtractInfo

Extract all meta information from an image.

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

=over 4

=item Inputs:

L</ExtractInfo> takes exactly the same arguments as L</ImageInfo>.  The only
difference is that a list of tag keys is not returned if an ARRAY reference
is given.  The following options are effective in the call to
L</ExtractInfo>:

Binary, Charset, CharsetID3, CharsetIPTC, Composite, ExtractEmbedded,
FastScan, FixBase, HtmlDump, HtmlDumpBase, IgnoreMinorErrors, Lang,
LargeFileSupport, MakerNotes, ScanForXMP, Struct, TextOut, Unknown and
Verbose.

=item Return Value:

1 if this was a recognized file format, 0 otherwise (and 'Error' tag set).

=back

=head2 GetInfo

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

    # get image width and hieght only
    $info = $exifTool->GetInfo('ImageWidth', 'ImageHeight');

    # get information for all tags in list (list updated with tags found)
    $info = $exifTool->GetInfo(\@ioTagList);

    # get all information in Author or Location groups
    $info = $exifTool->GetInfo({Group2 => ['Author', 'Location']});

=over 4

=item Inputs:

Inputs are the same as L</ExtractInfo> and L</ImageInfo> except that an
image can not be specified.  Options in effect are:

Charset, CoordFormat, DateFormat, Duplicates, Escape, Exclude, Group#, Lang,
List, ListSep, StrictDate, PrintConv, Sort (if a tag list reference is
given) and StrictDate.

=item Return Value:

Reference to information hash, the same as with L</ImageInfo>.

=back

=head2 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 L</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 L</SetNewValue> again.

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

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

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

=over 4

=item Inputs:

0) ExifTool object reference

1) Source file name, file reference, scalar reference, or undef to create a
file from scratch

2) [optional] Destination file name, file reference, scalar reference, or
undef to overwrite the original file

3) [optional] Destination file type

=item Return Value:

1 if file was written OK, 2 if file was written but no changes made, 0 on
file write error.

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.  Calling this routine clears any pre-existing
Error and Warning tags.

    $errorMessage = $exifTool->GetValue('Error');
    $warningMessage = $exifTool->GetValue('Warning');

=item Notes:

The source file name may be undefined to create a file from scratch
(currently only XMP, MIE, ICC, VRD and EXIF files can be created in this way
-- see L</CanCreate> for details).  If undefined, the destination file type
is required unless the type can be determined from the destination file
name.

If a destination file name is given, the specified file must not exist
because an existing destination file will not be overwritten.  The
destination file name may be undefined to overwrite the original file (make
sure you have backups!).  In this case, if a source file name is provided, a
temporary file is created and renamed to replace the source file if no
errors occurred while writing.  Otherwise, if a source file reference or
scalar reference is used, the image is first written to memory then copied
back to replace the original if there were no errors.

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

On Mac OS systems, the file resource fork is preserved if this routine is
called with a source file name.

=back

The following ExifTool options are effective in the call to L</WriteInfo>:

ByteOrder, Charset, CharsetID3, CharsetIPTC, Compact, Compress, FixBase,
IgnoreMinorErrors and Verbose.

=head2 CombineInfo

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

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

=over 4

=item Inputs:

0) ExifTool object reference

1-N) Information hash references

=back

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.

=head2 GetTagList

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

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

=over 4

=item Inputs:

0) ExifTool object reference,

1) [optional] Information hash reference or tag list reference,

2) [optional] Sort order ('File', 'Input', 'Alpha' or 'Group#').

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

=item Return Values:

A list of tag keys in the specified order.

=back

=head2 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 L</ImageInfo>,
L</ExtractInfo> or L</GetInfo> for this object.

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

=over 4

=item Inputs:

0) ExifTool object reference

1) [optional] Sort order ('File', 'Input', 'Alpha' or 'Group#')

If sort order is not specified, the sort order from the ExifTool options is
used.

=item Return Values:

A list of tag keys in the specified order.

=back

=head2 GetRequestedTags

Get list of requested tags.  These are the tags that were specified in the
arguments of the most recent call to L</ImageInfo>, L</ExtractInfo> or
L</GetInfo>, including tags specified via a tag list reference. Shortcut
tags are expanded in the list.

    @tags = $exifTool->GetRequestedTags();

=over 4

=item Inputs:

(none)

=item Return Values:

List of requested tag keys in the same order that the tags were specified.
Note that this list will be empty if tags were not specifically requested
(ie. If extracting all tags).

=back

=head2 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 same as the
values returned by L</ImageInfo> and L</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 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, L</GetValue> always returns
the list itself.

Note that L</GetValue> requires a case-sensitive tag key as an argument.  To
retrieve tag information based on a case-insensitive tag name (with an
optional group specifier), use L</GetInfo> instead.

    # 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');

=over 4

=item 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.

=item Return Values:

The value of the specified tag.  If the tag represents a list of values and
the List option is disabled then PrintConv returns a 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, or hash references if the Struct option is set.

Note: It is possible for L</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.

=back

=head2 SetNewValue

Set the new value for a tag.  The routine may be called multiple times to
set the values of many tags before using L</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.

    # 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);

    # set keywords (a List-type tag) with two new values
    $exifTool->SetNewValue(Keywords => 'word1');
    $exifTool->SetNewValue(Keywords => 'word2');
    # equivalent, but set both in one call using an array reference
    $exifTool->SetNewValue(Keywords => ['word1','word2']);

    # add a keyword without replacing existing keywords in the file
    $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);

    # write a tag only if it had a specific value
    # (the order of the following calls is not significant)
    $exifTool->SetNewValue(Title => $oldVal, DelValue => 1);
    $exifTool->SetNewValue(Title => $newVal);

    # write tag by numerical value
    $exifTool->SetNewValue(Orientation => 6, Type => 'ValueConv');
    $exifTool->SetNewValue('Orientation#' => 6);  # (equivalent)

    # delete all but EXIF tags
    $exifTool->SetNewValue('*');  # delete all...
    $exifTool->SetNewValue('EXIF:*', undef, Replace => 2); # ...but EXIF

=over 4

=item Inputs:

0) ExifTool object reference

1) [optional] Tag key or tag name, or undef 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. 'EXIF:Artist'), which is equivalent to using a Group
option argument.  Also, a '#' may be appended to the tag name (ie.
'EXIF:Orientation#'), with the same effect as setting Type to 'ValueConv'.

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.
Integer values may be specified in hexadecimal (with a leading '0x'), and
simple rational values may be specified as fractions.

3-N) [optional] SetNewValue option/value pairs (see below).

=item SetNewValue Options:

=over 4

=item AddValue

Specifies that the value be added to an existing list rather than replacing
the list.  Valid values are 0 or 1.  Default is 0.

=item DelValue

Delete the existing tag if it has the specified value.  Valid values are
0 or 1.  Default is 0.

=item EditGroup

Create tags in existing groups only.  Don't create new group.  Valid values
are 0 and 1.  Default is 0.

=item EditOnly

Edit tag only if it already exists.  Don't create new tag.  Valid values are
0 and 1.  Default is 0.

=item Group

Specifies group name where tag should be written.  If not specified, tag is
written to highest priority group as specified by L</SetNewGroups>.  Any
family 0 or 1 group name may be used.  Case is not significant.

=item NoShortcut

Disables default behaviour of looking up tag in shortcuts if not found
otherwise.

=item Protected

Bit mask for tag protection levels to write.  Bit 0x01 allows writing of
'unsafe' tags (ie. tags not copied automatically via
L</SetNewValuesFromFile>).  Bit 0x02 allows writing of 'protected' tags, and
should only be used internally by ExifTool.  See
L<Image::ExifTool::TagNames|Image::ExifTool::TagNames>, for a list of tag
names indicating 'unsafe' and 'protected' tags.  Default is 0.

=item Replace

Flag to replace the previous new value for this tag (ie. replace the value
set in a previous call to L</SetNewValue>).  Valid values are 0 (don't
replace), 1 (replace with specified new value) or 2 (reset previous new
value only).

=item Shift

Shift the tag by the specified value.  Currently only date/time tags can be
shifted.  Undefined for no shift, 1 for a positive shift, or -1 for a
negative shift.  If 0, the shift is applied only if the tag is shiftable,
and the shift is positive if AddValue is set, or negative if DelValue is
set.  Default is undef.  See
L<Image::ExifTool::Shift.pl|Image::ExifTool::Shift.pl> for more information.

=item Type

The type of value being set.  Valid values are PrintConv, ValueConv or Raw.
Default is PrintConv if the L</PrintConv> Option is set, otherwise
ValueConv.

=back

=item Return Values:

In scalar context, returns the number of tags set and error messages are
printed to STDERR.  In list context, returns the number of tags set and the
error string.

=item Notes:

When deleting groups of tags, the Replace option may be used as in the last
example above to exclude specific groups from a mass delete.  However, this
technique may not be used to exclude individual tags.  Instead, use
L</SetNewValuesFromFile> to recover the values of individual tags after
deleting a group.

=back

The following ExifTool options are effective in the call to L</SetNewValue>:

Charset, Escape, IgnoreMinorErrors, Lang, ListSep, ListSplit, PrintConv and
Verbose.

=head2 SetNewValuesFromFile

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

    # 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, @tags);

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

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

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

    # set keywords list from the values of multiple tags
    $exifTool->SetNewValuesFromFile($file, { Replace => 0 },
        'keywords<xmp:subject', 'keywords<filename');

    # copy all EXIF information, preserving the original IFD
    # (without '>*.*' tags would be copied to the preferred EXIF IFD)
    $exifTool->SetNewValuesFromFile($file, 'EXIF:*>*:*');

=over 4

=item Inputs:

0) ExifTool object reference

1) File name, file reference, or scalar reference

2-N) [optional] List of tag names to set or options hash references.  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'), or a trailing '#' causes the ValueConv value to
be copied (same as setting the Type option to 'ValueConv' for this tag
only).  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
'DSTTAGE<lt>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.
'CommentE<lt>the file is $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 L</MissingTagValue> option.)  Multiple options hash references may be
passed to set different options for different tags. Options apply to
subsequent tags in the argument list.

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.  When '*' is used for a group name, the family 1 group of
the original tag is preserved.  (For example, specifying '*:*' copies all
information while preserving the original family 1 groups.)

=item SetNewValuesFromFile Options:

The options are the same was for L</SetNewValue>, and are passed directly
to L</SetNewValue> internally, with a few exceptions:

- The Replace option defaults to 1 instead of 0 as with L</SetNewValue>.

- The AddValue or DelValue option is set for individual tags if '+>' or '->'
(or '+E<lt>' or '-E<lt>') are used.

- The Group option is set for tags where a group name is given.

- The Protected flag is set to 1 for individually specified tags.

- The Type option also applies to extracted tags.

=item Return Values:

A hash of information that was set successfully.  May include Warning or
Error entries if there were problems reading the input file.

=item 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, in a separate call to L</WriteInfo>

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.

The Duplicates option is always in effect for tags extracted from the source
file using this routine.

=back

=head2 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.

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

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

=over 4

=item Inputs:

0) ExifTool object reference

1) Tag name (case sensitive, group names not allowed)

=item Return Values:

List of new Raw tag values, or first value in list when called in scalar
context.  The list may be empty either if the tag isn't being written, or if
it is being deleted (ie. if L</SetNewValue> was called without a value).

=back

=head2 CountNewValues

Return the total number of new values set.

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

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Values:

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.

=back

=head2 SaveNewValues

Save state of new values to be later restored by L</RestoreNewValues>.

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

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Value:

None.

=back

=head2 RestoreNewValues

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

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Value:

None.

=back

=head2 SetFileModifyDate

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

    $exifTool->SetNewValue(FileModifyDate => '2000:01:02 03:04:05-05:00',
                           Protected => 1);
    $result = $exifTool->SetFileModifyDate($file);

=over 4

=item Inputs:

0) ExifTool object reference

1) File name

2) [optional] Base time if applying shift (days before $^T)

=item Return Value:

1 if the time was changed, 0 if nothing was done, or -1 if there was an
error setting the time.

=item Notes:

Equivalent to, but more efficient than calling L</WriteInfo> when only the
FileModifyDate tag has been set.  If a timezone is not specified in the
FileModifyDate value, local time is assumed.  When shifting FileModifyDate,
the time of the original file is used unless an optional base time is
specified.

=back

=head2 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.

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

=over 4

=item Inputs:

0) ExifTool object reference

1) Current file name

2) [optional] New file name

=item Return Value:

1 if the file name or directory was changed, 0 if nothing was done, or -1 if
there was an error renaming the file.

=item Notes:

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

=back

=head2 SetNewGroups

Set the order of the preferred groups when adding new information.  In
subsequent calls to L</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 L</SetNewValue> and if the tag name exists in more
than one group.  The default order is EXIF, IPTC then XMP.  Any family 0
group name may be used.  Case is not significant.

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

=over 4

=item Inputs:

0) ExifTool object reference

1-N) Groups in order of priority.  If no groups are specified, the priorities
are reset to the defaults.

=item Return Value:

None.

=back

=head2 GetNewGroups

Get current group priority list.

    @groups = $exifTool->GetNewGroups();

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Values:

List of group names in order of write priority.  Highest priority first.

=back

=head2 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.  In list context, also returns a language
code for the tag if available and different from the default language (ie.
with alternate language entries for XMP "lang-alt" tags).

    $id = $exifTool->GetTagID($tag);
    ($id, $lang) = $exifTool->GetTagID($tag);

=over 4

=item Inputs:

0) ExifTool object reference

1) Tag key

=item Return Values:

In scalar context, returns the tag ID or '' if there is no ID for this tag.
In list context, returns the tag ID (or '') and the language code (or
undef).

=back

=head2 GetDescription

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

=over 4

=item Inputs:

0) ExifTool object reference

1) Tag key

=item Return Values:

A description for the specified tag.

=back

=head2 GetGroup

Get group name(s) for a specified tag.

    # return family 0 group name (ie. 'EXIF');
    $group = $exifTool->GetGroup($tag, 0);

    # return all groups (ie. qw{EXIF IFD0 Author Main})
    @groups = $exifTool->GetGroup($tag);

    # return groups as a string (ie. 'Main:IFD0:Author')
    $group = $exifTool->GetGroup($tag, ':3:1:2');

    # return groups as a simplified string (ie. 'IFD0:Author')
    $group = $exifTool->GetGroup($tag, '3:1:2');

=over 4

=item Inputs:

0) ExifTool object reference

1) Tag key

2) [optional] Group family number, or string of numbers separated by colons

=item Return Values:

Group name (or '' if tag has no group).  If no group family is specified,
L</GetGroup> returns the name of the group in family 0 when called in scalar
context, or the names of groups for all families in list context.  Returns a
string of group names separated by colons if the input group family contains
a colon.  The string is simplified to remove a leading 'Main:' and adjacent
identical group names unless the family string begins with a colon.

=item Notes:

The group family numbers are currently available:

    0) Information Type             (ie. EXIF, XMP, IPTC)
    1) Specific Location            (ie. IFD0, XMP-dc)
    2) Category                     (ie. Author, Time)
    3) Document Number              (ie. Main, Doc1, Doc3-2)
    4) Instance Number              (ie. Copy1, Copy2, Copy3...)

Families 0 and 1 are based on the file structure, and are similar except
that family 1 is more specific -- it 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 in the
L<GetAllGroups documentation|/GetAllGroups [static]>, 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.

Family 2 classifies information based on the logical category to which the
information refers.

Family 3 gives the document number when the L</ExtractEmbedded> option is
used.  Nested sub-documents (if they exist) are indicated by numbers
separated with dashes in the group name, to an arbitrary depth. (ie.
'Doc2-3-1' is the 1st sub-sub-document of the 3rd sub-document of the 2nd
embedded document of the main file.)

Family 4 provides a method for differentiating tags when multiple tags exist
with the same name in the same location.  The primary instance of a tag (the
tag extracted when the Duplicates option is disabled and no group is
specified) has no family 4 group name, but additional instances have have
family 4 group names of 'Copy1', 'Copy2', 'Copy3', etc.

See L</GetAllGroups [static]> for complete lists of group names.

=back

=head2 GetGroups

Get list of group names that exist in the specified information.

    @groups = $exifTool->GetGroups($info, 2);
    @groups = $exifTool->GetGroups('3:1');

=over 4

=item Inputs:

0) ExifTool object reference

1) [optional] Info hash ref (default is all extracted info)

2) [optional] Group family number, or string of numbers (default 0)

=item Return Values:

List of group names in alphabetical order. If information hash is not
specified, the group names are returned for all extracted information. See
L</GetGroup> for an description of family numbers and family number strings.

=back

=head2 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 L</ImageInfo> and L</ExtractInfo> if the
Composite option is set.

=over 4

=item Inputs:

0) ExifTool object reference

=item Return Values:

(none)

=item Notes:

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. Composite tags may need to read
data from the image for their value to be determined, so for these
L</BuildCompositeTags> must be called while the image is available.  This is
only a problem if L</ImageInfo> is called with a filename (as opposed to a
file reference or scalar reference) since in this case the file is closed
before L</ImageInfo> returns.  However if you enable the Composite option,
L</BuildCompositeTags> is called from within L</ImageInfo> before the file
is closed.

=back

=head2 GetTagName [static]

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

Note: "static" in the heading above indicates that the function does not
require an ExifTool object reference as the first argument.  All functions
documented below are also static.

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

=over 4

=item Inputs:

0) Tag key

=item Return Value:

Tag name.  This is the same as the tag key but has the instance number
removed.

=back

=head2 GetShortcuts [static]

Get a list of shortcut tags.

=over 4

=item Inputs:

(none)

=item Return Values:

List of shortcut tags (as defined in Image::ExifTool::Shortcuts).

=back

=head2 GetAllTags [static]

Get list of all available tag names.

    @tagList = Image::ExifTool::GetAllTags($group);

=over 4

=item Inputs:

0) [optional] Group name, or string of group names separated by colons

=item Return Values:

A list of all available tags in alphabetical order, or all tags in a
specified group or intersection of groups.  The group name is case
insensitive, and any group in families 0-2 may be used except for EXIF
family 1 groups (ie. the specific IFD).

=back

=head2 GetWritableTags [static]

Get list of all writable tag names.

    @tagList = Image::ExifTool::GetWritableTags($group);

=over 4

=item Inputs:

0) [optional] Group name, or string of group names separated by colons

=item Return Values:

A list of all writable tags in alphabetical order.  These are the tags for
which values may be set through L</SetNewValue>.  If a group name is given,
returns only writable tags in specified group(s).  The group name is case
insensitive, and any group in families 0-2 may be used except for EXIF
family 1 groups (ie. the specific IFD).

=back

=head2 GetAllGroups [static]

Get list of all group names in specified family.

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

=over 4

=item Inputs:

0) Group family number (0-4)

=item Return Values:

A list of all groups in the specified family in alphabetical order.

=back

Here is a complete list of groups for each of these families:

=over 4

=item Family 0 (Information Type):

AFCP, AIFF, APE, APP0, APP12, APP13, APP14, APP15, APP4, APP5, APP6, APP8,
ASF, BMP, CanonVRD, Composite, DICOM, DNG, DjVu, Ducky, EXE, EXIF, ExifTool,
FLAC, File, Flash, FlashPix, Font, FotoStation, GIF, GIMP, GeoTiff, H264,
HTML, ICC_Profile, ID3, IPTC, ITC, JFIF, JPEG, Jpeg2000, LNK, Leaf, M2TS,
MIE, MIFF, MNG, MPC, MPEG, MPF, MakerNotes, Matroska, Meta, PDF, PICT, PNG,
PSP, PhotoMechanic, Photoshop, PostScript, PrintIM, QuickTime, RAF, RIFF,
RSRC, RTF, Rawzor, Real, SVG, SigmaRaw, Stim, Vorbis, XML, XMP, ZIP

=item Family 1 (Specific Location):

AC3, AFCP, AIFF, APE, ASF, AVI1, Adobe, AdobeCM, BMP, CIFF, Canon,
CanonCustom, CanonRaw, CanonVRD, Casio, Chapter#, Composite, DICOM, DNG,
DjVu, DjVu-Meta, Ducky, EPPIM, EXE, EXIF, ExifIFD, ExifTool, FLAC, File,
Flash, FlashPix, Font, FotoStation, FujiFilm, GIF, GIMP, GPS, GeoTiff,
GlobParamIFD, GraphConv, H264, HP, HTML, HTML-dc, HTML-ncc, HTML-office,
HTML-prod, HTML-vw96, HTTP-equiv, ICC-chrm, ICC-clrt, ICC-header, ICC-meas,
ICC-meta, ICC-view, ICC_Profile, ICC_Profile#, ID3, ID3v1, ID3v1_Enh,
ID3v2_2, ID3v2_3, ID3v2_4, IFD0, IFD1, IPTC, IPTC#, ITC, InteropIFD, JFIF,
JPEG, JVC, Jpeg2000, KDC_IFD, Kodak, KodakBordersIFD, KodakEffectsIFD,
KodakIFD, KyoceraRaw, LNK, Leaf, LeafSubIFD, Leica, M2TS, MAC, MIE-Audio,
MIE-Camera, MIE-Canon, 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, MPF0, MPImage, MakerNotes, MakerUnknown, Matroska, MetaIFD, Microsoft,
Minolta, MinoltaRaw, NITF, Nikon, NikonCapture, NikonCustom, NikonScan,
Olympus, PDF, PICT, PNG, PSP, Panasonic, Pentax, PhotoMechanic, Photoshop,
PictureInfo, PostScript, PreviewIFD, PrintIM, ProfileIFD, QuickTime, RAF,
RAF2, RIFF, RMETA, RSRC, RTF, Rawzor, Real, Real-CONT, Real-MDPR, Real-PROP,
Real-RA3, Real-RA4, Real-RA5, Real-RJMD, Ricoh, SPIFF, SR2, SR2DataIFD,
SR2SubIFD, SRF#, SVG, Samsung, Sanyo, Scalado, Sigma, SigmaRaw, Sony,
SonyIDC, Stim, SubIFD, System, Track#, Version0, Vorbis, XML, XMP,
XMP-DICOM, XMP-MP, XMP-MP1, XMP-PixelLive, XMP-acdsee, XMP-album, XMP-aux,
XMP-cc, XMP-crs, XMP-dc, XMP-dex, XMP-digiKam, XMP-exif, XMP-iptcCore,
XMP-iptcExt, XMP-lr, XMP-mediapro, XMP-microsoft, XMP-pdf, XMP-pdfx,
XMP-photomech, XMP-photoshop, XMP-plus, XMP-prism, XMP-prl, XMP-pur,
XMP-rdf, XMP-swf, XMP-tiff, XMP-x, XMP-xmp, XMP-xmpBJ, XMP-xmpDM, XMP-xmpMM,
XMP-xmpNote, XMP-xmpPLUS, XMP-xmpRights, XMP-xmpTPg, ZIP

=item Family 2 (Category):

Audio, Author, Camera, Document, ExifTool, Image, Location, Other, Printing,
Time, Unknown, Video

=item Family 3 (Document Number):

Doc#, Main

=item Family 4 (Instance Number):

Copy#

=back

=head2 GetDeleteGroups [static]

Get list of all deletable group names.

    @delGroups = Image::ExifTool::GetDeleteGroups();

=over 4

=item Inputs:

None.

=item Return Values:

A list of deletable group names in alphabetical order.  The current list of
deletable group names is:

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

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 L</SetNewValue> with an undefined value and a tag
name like 'Trailer:*'.

=back

=head2 GetFileType [static]

Get type of file given file name.

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

=over 4

=item Inputs:

0) [optional] File name (or just an extension)

1) [optional]  Flag to return a description instead of a type

=item Return Value:

A string, based on the file extension, which indicates the basic format of
the file.  Note that some files may be based on other formats (like many RAW
image formats are based on TIFF).  In array context, may return more than
one file type if the file may be based on different formats.  Returns undef
if files with this extension are not yet supported by ExifTool.  Returns a
list of extensions for all recognized file types if no input extension is
specified.  Returns a more detailed description of the specific file format
when the description flag is set.

=back

=head2 CanWrite [static]

Can the specified file be written?

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

=over 4

=item Inputs:

0) File name or extension

=item Return Value:

True if ExifTool supports writing files of this type (based on the file
extension).

=back

=head2 CanCreate [static]

Can the specified file be created?

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

=over 4

=item Inputs:

0) File name or extension

=item Return Value:

True if ExifTool can create files with this extension from scratch. 
Currently, this can only be done with XMP, MIE, ICC, VRD and EXIF files.

=back

=head1 CHARACTER ENCODINGS

Certain meta information formats allow coded character sets other than plain
ASCII.  When reading, 8-bit encodings are passed straight through ExifTool
without re-coding unless specified otherwise below, and multi-byte encodings
are converted according to the L</Charset> option ('UTF8' by default).  When
writing, the inverse conversions are performed.  See the L</Charset> option
for a list of valid character sets.

More specific details are given below about how character coding is handled
for EXIF, IPTC, XMP, PNG, ID3, PDF and MIE information:

=head2 EXIF

Most textual information in EXIF is stored in ASCII format, and ExifTool
does not convert these tags.  However it is not uncommon for applications to
write UTF-8 or other encodings where ASCII is expected, and ExifTool will
quite happily read/write any encoding without conversion.  For a few EXIF
tags (UserComment, GPSProcessingMethod and GPSAreaInformation) the stored
text may be encoded either in ASCII, Unicode (UCS-2) or JIS.  When reading
these tags, Unicode and JIS are converted to the character set specified by
the L</Charset> option.  Other encodings are not converted.  When writing,
text is stored as ASCII unless the string contains special characters, in
which case it is converted from the specified character set and stored as
Unicode.  ExifTool writes Unicode in native EXIF byte ordering by default,
but this may be changed by setting the ExifUnicodeByteOrder tag.  The EXIF
"XP" tags (XPTitle, XPComment, etc) are always stored as little-endian
Unicode, and are read and written using the specified character set.

=head2 IPTC

The value of the IPTC:CodedCharacterSet tag determines how the internal IPTC
string values are interpreted.  If CodedCharacterSet exists and has a value
of 'UTF8' (or 'ESC % G') then string values are assumed to be stored as
UTF-8, otherwise Windows Latin1 (cp1252, 'Latin') coding is assumed by
default, but this can be changed with the L</CharsetIPTC> option.  When
reading, these strings are converted to the character set specified by the
L</Charset> option.  When writing, the inverse conversions are performed. 
No conversion is done if the internal (IPTC) and external (ExifTool)
character sets are the same.  Note that ISO 2022 character set shifting is
not supported.  Instead, a warning is issued and the string is not converted
if an ISO 2022 shift code is found.  See L<http://www.iptc.org/IIM/> for the
official IPTC specification.

=head2 XMP

Exiftool reads XMP encoded as UTF-8, UTF-16 or UTF-32, and converts them all
to UTF-8 internally.  Also, all XML character entity references and numeric
character references are converted.  When writing, ExifTool always encodes
XMP as UTF-8, converting the following 5 characters to XML character
references: E<amp> E<lt> E<gt> E<39> E<quot>.  By default no further
conversion is performed, however if the L</Charset> option is other than
'UTF8' then text is converted to/from a specified character set when
reading/writing.

=head2 PNG

L<PNG TextualData tags|Image::ExifTool::TagNames/"PNG TextualData Tags"> are
stored as tEXt, zTXt and iTXt chunks in PNG images.  The tEXt and zTXt
chunks use ISO 8859-1 encoding, while iTXt uses UTF-8.  When reading,
ExifTool converts all PNG textual data to the character set specified by the
L</Charset> option.  When writing, ExifTool generates a tEXt chunk (or zTXt
with the L</Compress> option) if the text doesn't contain special characters
or if Latin encoding is specified; otherwise an iTXt chunk is used and the
text is converted from the specified character set and stored as UTF-8.

=head2 ID3

The ID3v1 specification officially supports only ISO 8859-1 encoding (a
subset of Windows Latin1), although some applications may incorrectly use
other character sets.  By default ExifTool converts ID3v1 text from Latin to
the character set specified by the </Charset> option.  However, the internal
ID3v1 charset may be specified with the L</CharsetID3> option.  The encoding
for ID3v2 information is stored in the file, so ExifTool converts ID3v2 text
from this encoding to the character set specified by the L</Charset> option.
ExifTool does not currently write ID3 information.

=head2 PDF

PDF text strings are stored in either PDFDocEncoding (similar to Windows
Latin1) or Unicode (UCS-2).  When reading, ExifTool converts to the
character set specified by the L</Charset> option.  When writing, ExifTool
encodes input text from the specified character set as Unicode only if the
string contains special characters, otherwise PDFDocEncoding is used.

=head2 MIE

MIE strings are stored as either UTF-8 or ISO 8859-1. When reading, UTF-8
strings are converted according to the L</Charset> option, and ISO 8859-1
strings are never converted.  When writing, input strings are converted from
the specified character set to UTF-8.  The resulting strings are stored as
UTF-8 if they contain multi-byte UTF-8 character sequences, otherwise they
are stored as ISO 8859-1.

=head1 AUTHOR

Copyright 2003-2010, Phil Harvey

This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.

=head1 ACKNOWLEDGEMENTS

Many people have helped in the development of ExifTool through their bug
reports, comments and suggestions, and/or additions to the code.  See the
ACKNOWLEDGEMENTS in the individual Image::ExifTool modules and in
html/index.html of the Image::ExifTool distribution package for a list of
people who have contributed to this project.

=head1 SEE ALSO

L<exiftool(1)|exiftool>,
L<Image::ExifTool::TagNames(3pm)|Image::ExifTool::TagNames>,
L<Image::ExifTool::Shortcuts(3pm)|Image::ExifTool::Shortcuts>,
L<Image::ExifTool::Shift.pl|Image::ExifTool::Shift.pl>,
L<Image::Info(3pm)|Image::Info>,
L<Image::MetaData::JPEG(3pm)|Image::MetaData::JPEG>

=cut

# end
