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- #------------------------------------------------------------------------------
- # File: AFCP.pm
- #
- # Description: Read/write AFCP trailer
- #
- # Revisions: 12/26/2005 - P. Harvey Created
- #
- # References: 1) http://web.archive.org/web/20080828211305/http://www.tocarte.com/media/axs_afcp_spec.pdf
- #------------------------------------------------------------------------------
- package Image::ExifTool::AFCP;
- use strict;
- use vars qw($VERSION);
- use Image::ExifTool qw(:DataAccess :Utils);
- $VERSION = '1.07';
- sub ProcessAFCP($$);
- %Image::ExifTool::AFCP::Main = (
- PROCESS_PROC => \&ProcessAFCP,
- NOTES => q{
- AFCP stands for AXS File Concatenation Protocol, and is a poorly designed
- protocol for appending information to the end of files. This can be used as
- an auxiliary technique to store IPTC information in images, but is
- incompatible with some file formats.
- ExifTool will read and write (but not create) AFCP IPTC information in JPEG
- and TIFF images.
- See
- L<http://web.archive.org/web/20080828211305/http://www.tocarte.com/media/axs_afcp_spec.pdf>
- for the AFCP specification.
- },
- IPTC => { SubDirectory => { TagTable => 'Image::ExifTool::IPTC::Main' } },
- TEXT => 'Text',
- Nail => {
- Name => 'ThumbnailImage',
- Groups => { 2 => 'Preview' },
- # (the specification allows for a variable amount of padding before
- # the image after a 10-byte header, so look for the JPEG SOI marker,
- # otherwise assume a fixed 8 bytes of padding)
- RawConv => q{
- pos($val) = 10;
- my $start = ($val =~ /\xff\xd8\xff/g) ? pos($val) - 3 : 18;
- my $img = substr($val, $start);
- return $self->ValidateImage(\$img, $tag);
- },
- },
- PrVw => {
- Name => 'PreviewImage',
- Groups => { 2 => 'Preview' },
- RawConv => q{
- pos($val) = 10;
- my $start = ($val =~ /\xff\xd8\xff/g) ? pos($val) - 3 : 18;
- my $img = substr($val, $start);
- return $self->ValidateImage(\$img, $tag);
- },
- },
- );
- #------------------------------------------------------------------------------
- # Read/write AFCP information in a file
- # Inputs: 0) ExifTool object reference, 1) dirInfo reference
- # (Set 'ScanForAFCP' member in dirInfo to scan from current position for AFCP)
- # Returns: 1 on success, 0 if this file didn't contain AFCP information
- # -1 on write error or if the offsets were incorrect on reading
- # - updates DataPos to point to actual AFCP start if ScanForAFCP is set
- # - updates DirLen to trailer length
- # - returns Fixup reference in dirInfo hash when writing
- sub ProcessAFCP($$)
- {
- my ($et, $dirInfo) = @_;
- my $raf = $$dirInfo{RAF};
- my $curPos = $raf->Tell();
- my $offset = $$dirInfo{Offset} || 0; # offset from end of file
- my $rtnVal = 0;
- NoAFCP: for (;;) {
- my ($buff, $fix, $dirBuff, $valBuff, $fixup, $vers);
- # look for AXS trailer
- last unless $raf->Seek(-12-$offset, 2) and
- $raf->Read($buff, 12) == 12 and
- $buff =~ /^(AXS(!|\*))/;
- my $endPos = $raf->Tell();
- my $hdr = $1;
- SetByteOrder($2 eq '!' ? 'MM' : 'II');
- my $startPos = Get32u(\$buff, 4);
- if ($raf->Seek($startPos, 0) and $raf->Read($buff, 12) == 12 and $buff =~ /^$hdr/) {
- $fix = 0;
- } else {
- $rtnVal = -1;
- # look for start of AXS trailer if 'ScanForAFCP'
- last unless $$dirInfo{ScanForAFCP} and $raf->Seek($curPos, 0);
- my $actualPos = $curPos;
- # first look for header right at current position
- for (;;) {
- last if $raf->Read($buff, 12) == 12 and $buff =~ /^$hdr/;
- last NoAFCP if $actualPos != $curPos;
- # scan for AXS header (could be after preview image)
- for (;;) {
- my $buf2;
- $raf->Read($buf2, 65536) or last NoAFCP;
- $buff .= $buf2;
- if ($buff =~ /$hdr/g) {
- $actualPos += pos($buff) - length($hdr);
- last; # ok, now go back and re-read header
- }
- $buf2 = substr($buf2, -3); # only need last 3 bytes for next test
- $actualPos += length($buff) - length($buf2);
- $buff = $buf2;
- }
- last unless $raf->Seek($actualPos, 0); # seek to start of AFCP
- }
- # calculate shift for fixing AFCP offsets
- $fix = $actualPos - $startPos;
- }
- # set variables returned in dirInfo hash
- $$dirInfo{DataPos} = $startPos + $fix; # actual start position
- $$dirInfo{DirLen} = $endPos - ($startPos + $fix);
- $rtnVal = 1;
- my $verbose = $et->Options('Verbose');
- my $out = $et->Options('TextOut');
- my $outfile = $$dirInfo{OutFile};
- if ($outfile) {
- # allow all AFCP information to be deleted
- if ($$et{DEL_GROUP}{AFCP}) {
- $verbose and print $out " Deleting AFCP\n";
- ++$$et{CHANGED};
- last;
- }
- $dirBuff = $valBuff = '';
- require Image::ExifTool::Fixup;
- $fixup = $$dirInfo{Fixup};
- $fixup or $fixup = $$dirInfo{Fixup} = new Image::ExifTool::Fixup;
- $vers = substr($buff, 4, 2); # get version number
- } else {
- $et->DumpTrailer($dirInfo) if $verbose or $$et{HTML_DUMP};
- }
- # read AFCP directory data
- my $numEntries = Get16u(\$buff, 6);
- my $dir;
- unless ($raf->Read($dir, 12 * $numEntries) == 12 * $numEntries) {
- $et->Error('Error reading AFCP directory', 1);
- last;
- }
- if ($verbose > 2 and not $outfile) {
- my $dat = $buff . $dir;
- print $out " AFCP Directory:\n";
- HexDump(\$dat, undef,
- Addr => $$dirInfo{DataPos},
- Width => 12,
- Prefix => $$et{INDENT},
- Out => $out,
- );
- }
- $fix and $et->Warn("Adjusted AFCP offsets by $fix", 1);
- #
- # process AFCP directory
- #
- my $tagTablePtr = GetTagTable('Image::ExifTool::AFCP::Main');
- my ($index, $entry);
- for ($index=0; $index<$numEntries; ++$index) {
- my $entry = 12 * $index;
- my $tag = substr($dir, $entry, 4);
- my $size = Get32u(\$dir, $entry + 4);
- my $offset = Get32u(\$dir, $entry + 8);
- if ($size < 0x80000000 and
- $raf->Seek($offset+$fix, 0) and
- $raf->Read($buff, $size) == $size)
- {
- if ($outfile) {
- # rewrite this information
- my $tagInfo = $et->GetTagInfo($tagTablePtr, $tag);
- if ($tagInfo and $$tagInfo{SubDirectory}) {
- my %subdirInfo = (
- DataPt => \$buff,
- DirStart => 0,
- DirLen => $size,
- DataPos => $offset + $fix,
- Parent => 'AFCP',
- );
- my $subTable = GetTagTable($tagInfo->{SubDirectory}->{TagTable});
- my $newDir = $et->WriteDirectory(\%subdirInfo, $subTable);
- if (defined $newDir) {
- $size = length $newDir;
- $buff = $newDir;
- }
- }
- $fixup->AddFixup(length($dirBuff) + 8);
- $dirBuff .= $tag . Set32u($size) . Set32u(length $valBuff);
- $valBuff .= $buff;
- } else {
- # extract information
- $et->HandleTag($tagTablePtr, $tag, $buff,
- DataPt => \$buff,
- Size => $size,
- Index => $index,
- DataPos => $offset + $fix,
- );
- }
- } else {
- $et->Warn("Bad AFCP directory");
- $rtnVal = -1 if $outfile;
- last;
- }
- }
- if ($outfile and length($dirBuff)) {
- my $outPos = Tell($outfile); # get current outfile position
- # apply fixup to directory pointers
- my $valPos = $outPos + 12; # start of value data
- $fixup->{Shift} += $valPos + length($dirBuff);
- $fixup->ApplyFixup(\$dirBuff);
- # write the AFCP header, directory, value data and EOF record (with zero checksums)
- Write($outfile, $hdr, $vers, Set16u(length($dirBuff)/12), Set32u(0),
- $dirBuff, $valBuff, $hdr, Set32u($outPos), Set32u(0)) or $rtnVal = -1;
- # complete fixup so the calling routine can apply further shifts
- $fixup->AddFixup(length($dirBuff) + length($valBuff) + 4);
- $fixup->{Start} += $valPos;
- $fixup->{Shift} -= $valPos;
- }
- last;
- }
- return $rtnVal;
- }
- 1; # end
- __END__
- =head1 NAME
- Image::ExifTool::AFCP - Read/write AFCP trailer
- =head1 SYNOPSIS
- This module is used by Image::ExifTool
- =head1 DESCRIPTION
- This module contains definitions required by Image::ExifTool to extract
- information from the AFCP trailer. Although the AFCP specification is
- compatible with various file formats, ExifTool currently only processes AFCP
- in JPEG images.
- =head1 NOTES
- AFCP is a specification which allows meta information (including IPTC) to be
- appended to the end of a file.
- It is a poorly designed protocol because (like TIFF) it uses absolute
- offsets to specify data locations. This is a huge blunder because it makes
- the AFCP information dependent on the file length, so it is easily
- invalidated by image editing software which doesn't recognize the AFCP
- trailer to fix up these offsets when the file length changes. ExifTool will
- attempt to fix these invalid offsets if possible.
- Scanning for AFCP information may be time consuming, especially when reading
- from a sequential device, since the information is at the end of the file.
- In these instances, the ExifTool FastScan option may be used to disable
- scanning for AFCP information.
- =head1 AUTHOR
- Copyright 2003-2016, 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 REFERENCES
- =over 4
- =item L<http://www.tocarte.com/media/axs_afcp_spec.pdf>
- =back
- =head1 SEE ALSO
- L<Image::ExifTool::TagNames/AFCP Tags>,
- L<Image::ExifTool(3pm)|Image::ExifTool>
- =cut
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