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#------------------------------------------------------------------------------
# File: FITS.pm
#
# Description: Read Flexible Image Transport System metadata
#
# Revisions: 2018/03/07 - P. Harvey Created
#
# References: 1) https://fits.gsfc.nasa.gov/fits_standard.html
#------------------------------------------------------------------------------
package Image::ExifTool::FITS;
use strict;
use vars qw($VERSION);
use Image::ExifTool qw(:DataAccess :Utils);
$VERSION = '1.00';
# FITS tags (ref 1)
%Image::ExifTool::FITS::Main = (
GROUPS => { 2 => 'Image' },
NOTES => q{
This table lists some standard Flexible Image Transport System (FITS) tags,
but ExifTool will extract any other tags found. See
L<https://fits.gsfc.nasa.gov/fits_standard.html> for the specification.
},
TELESCOP => 'Telescope',
BACKGRND => 'Background',
INSTRUME => 'Instrument',
OBJECT => 'Object',
OBSERVER => 'Observer',
DATE => { Name => 'CreateDate', Groups => { 2 => 'Time' } },
AUTHOR => { Name => 'Author', Groups => { 2 => 'Author' } },
REFERENC => 'Reference',
'DATE-OBS'=> { Name => 'ObservationDate', Groups => { 2 => 'Time' } },
'TIME-OBS'=> { Name => 'ObservationTime', Groups => { 2 => 'Time' } },
'DATE-END'=> { Name => 'ObservationDateEnd', Groups => { 2 => 'Time' } },
'TIME-END'=> { Name => 'ObservationTimeEnd', Groups => { 2 => 'Time' } },
);
#------------------------------------------------------------------------------
# Read information in a FITS document
# Inputs: 0) ExifTool ref, 1) dirInfo ref
# Returns: 1 on success, 0 if this wasn't a valid FITS file
sub ProcessFITS($$)
{
my ($et, $dirInfo) = @_;
my $raf = $$dirInfo{RAF};
my ($buff, $tag, $continue);
return 0 unless $raf->Read($buff, 80) == 80 and $buff =~ /^SIMPLE = {20}T/;
$et->SetFileType();
my $tagTablePtr = GetTagTable('Image::ExifTool::FITS::Main');
for (;;) {
$raf->Read($buff, 80) == 80 or $et->Warn('Truncated FITS header'), last;
my $key = substr($buff, 0, 8);
$key =~ s/ +$//; # remove trailing space from key
if ($key eq 'CONTINUE') {
defined $continue or $et->WarnOnce('Unexpected FITS CONTINUE keyword'), next;
} else {
if (defined $continue) {
# the previous value wasn't continued, so store with the trailing '&'
$et->HandleTag($tagTablePtr, $tag, $continue . '&');
undef $continue;
}
last if $key eq 'END';
# make sure the key is valid
$key =~ /^[-_A-Z0-9]*$/ or $et->Warn('Format error in FITS header'), last;
next unless substr($buff,8,2) eq '= '; # ignore comment lines
# save tag name (avoiding potential conflict with ExifTool variables)
$tag = $Image::ExifTool::specialTags{$key} ? "_$key" : $key;
# add to tag table if necessary
unless ($$tagTablePtr{$tag}) {
my $name = ucfirst lc $tag; # make tag name lower case with leading capital
$name =~ s/_(.)/\U$1/g; # remove all '_' and capitalize subsequent letter
AddTagToTable($tagTablePtr, $tag, { Name => $name });
}
}
my $val = substr($buff, 10);
# parse quoted values
if ($val =~ /^'(.*?)'(.*)/) {
($val, $buff) = ($1, $2);
while ($buff =~ /^('.*?)'(.*)/) { # handle escaped quotes
$val .= $1;
$buff = $2;
}
$val =~ s/ +$//; # remove trailing spaces
if (defined $continue) {
$val = $continue . $val;
undef $continue;
}
# check for possible continuation, removing trailing '&'
$val =~ s/\&$// and $continue = $val, next;
} elsif (defined $continue) {
$et->WarnOnce('Invalid FITS CONTINUE value');
next;
} else {
$val =~ s/ *(\/.*)?$//; # remove trailing spaces and comment
next unless length $val; # ignore undefined values
$val =~ s/^ +//; # remove leading spaces
# re-format floating-point values to use 'e'
$val =~ tr/DE/e/ if $val =~ /^[+-]?(?=\d|\.\d)\d*(\.\d*)?([ED]([+-]?\d+))?$/;
}
$et->HandleTag($tagTablePtr, $tag, $val);
}
return 1;
}
1; # end
__END__
=head1 NAME
Image::ExifTool::FITS - Read Flexible Image Transport System metadata
=head1 SYNOPSIS
This module is used by Image::ExifTool
=head1 DESCRIPTION
This module contains definitions required by Image::ExifTool to read meta
information from FITS (Flexible Image Transport System) images.
=head1 AUTHOR
Copyright 2003-2021, Phil Harvey (philharvey66 at gmail.com)
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
=head1 REFERENCES
=over 4
=item L<https://fits.gsfc.nasa.gov/fits_standard.html>
=back
=head1 SEE ALSO
L<Image::ExifTool::TagNames/FITS Tags>,
L<Image::ExifTool(3pm)|Image::ExifTool>
=cut
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