#------------------------------------------------------------------------------ # 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 = '1.08'; sub ProcessAFCP($$); %Image::ExifTool::AFCP::Main = ( PROCESS_PROC => \&ProcessAFCP, NOTES => q{ AFCP stands for AXS File Concatenation Protocol, and is a poorly designed protocol for appending information to the end of files. This can be used as an auxiliary technique to store IPTC information in images, but is incompatible with some file formats. ExifTool will read and write (but not create) AFCP IPTC information in JPEG and TIFF images. See L for the AFCP specification. }, IPTC => { SubDirectory => { TagTable => 'Image::ExifTool::IPTC::Main' } }, TEXT => 'Text', Nail => { Name => 'ThumbnailImage', Groups => { 2 => 'Preview' }, # (the specification allows for a variable amount of padding before # the image after a 10-byte header, so look for the JPEG SOI marker, # otherwise assume a fixed 8 bytes of padding) RawConv => q{ pos($val) = 10; my $start = ($val =~ /\xff\xd8\xff/g) ? pos($val) - 3 : 18; my $img = substr($val, $start); return $self->ValidateImage(\$img, $tag); }, }, PrVw => { Name => 'PreviewImage', Groups => { 2 => 'Preview' }, RawConv => q{ pos($val) = 10; my $start = ($val =~ /\xff\xd8\xff/g) ? pos($val) - 3 : 18; my $img = substr($val, $start); return $self->ValidateImage(\$img, $tag); }, }, ); #------------------------------------------------------------------------------ # Read/write AFCP information in a file # Inputs: 0) ExifTool object reference, 1) dirInfo reference # (Set 'ScanForAFCP' member in dirInfo to scan from current position for AFCP) # Returns: 1 on success, 0 if this file didn't contain AFCP information # -1 on write error or if the offsets were incorrect on reading # - updates DataPos to point to actual AFCP start if ScanForAFCP is set # - updates DirLen to trailer length # - returns Fixup reference in dirInfo hash when writing sub ProcessAFCP($$) { 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 $$et{HTML_DUMP}; } # read AFCP directory data my $numEntries = Get16u(\$buff, 6); my $dir; unless ($raf->Read($dir, 12 * $numEntries) == 12 * $numEntries) { $et->Error('Error reading AFCP directory', 1); last; } if ($verbose > 2 and not $outfile) { my $dat = $buff . $dir; print $out " AFCP Directory:\n"; $et->VerboseDump(\$dat, Addr => $$dirInfo{DataPos}, Width => 12); } $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 2003-2018, 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 =back =head1 SEE ALSO L, L =cut