#------------------------------------------------------------------------------
# File:         WritePNG.pl
#
# Description:  Write PNG meta information
#
# Revisions:    09/16/2005 - P. Harvey Created
#
# References:   1) http://www.libpng.org/pub/png/spec/1.2/
#------------------------------------------------------------------------------
package Image::ExifTool::PNG;

use strict;

#------------------------------------------------------------------------------
# Calculate CRC or update running CRC (ref 1)
# Inputs: 0) data reference, 1) running crc to update (undef initially)
#         2) data position (undef for 0), 3) data length (undef for all data),
# Returns: updated CRC
my @crcTable;
sub CalculateCRC($;$$$)
{
    my ($dataPt, $crc, $pos, $len) = @_;
    $crc = 0 unless defined $crc;
    $pos = 0 unless defined $pos;
    $len = length($$dataPt) - $pos unless defined $len;
    $crc ^= 0xffffffff;         # undo 1's complement
    # build lookup table unless done already
    unless (@crcTable) {
        my ($c, $n, $k);
        for ($n=0; $n<256; ++$n) {
            for ($k=0, $c=$n; $k<8; ++$k) {
                $c = ($c & 1) ? 0xedb88320 ^ ($c >> 1) : $c >> 1;
            }
            $crcTable[$n] = $c;
        }
    }
    # calculate the CRC
    foreach (unpack("x${pos}C$len", $$dataPt)) {
        $crc = $crcTable[($crc^$_) & 0xff] ^ ($crc >> 8);
    }
    return $crc ^ 0xffffffff;   # return 1's complement
}

#------------------------------------------------------------------------------
# Encode data in ASCII Hex
# Inputs: 0) input data reference
# Returns: Hex-encoded data (max 72 chars per line)
sub HexEncode($)
{
    my $dataPt = shift;
    my $len = length($$dataPt);
    my $hex = '';
    my $pos;
    for ($pos = 0; $pos < $len; $pos += 36) {
        my $n = $len - $pos;
        $n > 36 and $n = 36;
        $hex .= unpack('H*',substr($$dataPt,$pos,$n)) . "\n";
    }
    return $hex;
}

#------------------------------------------------------------------------------
# Write profile chunk (possibly compressed if Zlib is available)
# Inputs: 0) outfile, 1) Raw profile type (SCALAR ref for iCCP name), 2) data ref
#         3) profile header type (undef if not a text profile)
# Returns: 1 on success
sub WriteProfile($$$;$)
{
    my ($outfile, $rawType, $dataPt, $profile) = @_;
    my ($buff, $prefix, $chunk, $deflate);
    if ($rawType ne $stdCase{exif} and eval { require Compress::Zlib }) {
        $deflate = Compress::Zlib::deflateInit();
    }
    if (not defined $profile) {
        # write ICC profile as compressed iCCP chunk if possible
        if (ref $rawType) {
            return 0 unless $deflate;
            $chunk = 'iCCP';
            $prefix = "$$rawType\0\0";
        } else {
            $chunk = $rawType;
            if ($rawType eq $stdCase{zxif}) {
                $prefix = "\0" . pack('N', length $$dataPt); # (proposed compressed EXIF)
            } else {
                $prefix = '';   # standard EXIF
            }
        }
        if ($deflate) {
            $buff = $deflate->deflate($$dataPt);
            return 0 unless defined $buff;
            $buff .= $deflate->flush();
            $dataPt = \$buff;
        }
    } else {
        # write as ASCII-hex encoded profile in tEXt or zTXt chunk
        my $txtHdr = sprintf("\n$profile profile\n%8d\n", length($$dataPt));
        $buff = $txtHdr . HexEncode($dataPt);
        $chunk = 'tEXt';         # write as tEXt if deflate not available
        $prefix = "Raw profile type $rawType\0";
        $dataPt = \$buff;
        # write profile as zTXt chunk if possible
        if ($deflate) {
            my $buf2 = $deflate->deflate($buff);
            if (defined $buf2) {
                $dataPt = \$buf2;
                $buf2 .= $deflate->flush();
                $chunk = 'zTXt';
                $prefix .= "\0";    # compression type byte (0=deflate)
            }
        }
    }
    my $hdr = pack('Na4', length($prefix) + length($$dataPt), $chunk) . $prefix;
    my $crc = CalculateCRC(\$hdr, undef, 4);
    $crc = CalculateCRC($dataPt, $crc);
    return Write($outfile, $hdr, $$dataPt, pack('N',$crc));
}

#------------------------------------------------------------------------------
# Add iCCP-related chunks to the PNG image if necessary (must come before PLTE and IDAT)
# Inputs: 0) ExifTool object ref, 1) output file or scalar ref
# Returns: true on success
sub Add_iCCP($$)
{
    my ($et, $outfile) = @_;
    if ($$et{ADD_DIRS}{ICC_Profile}) {
        # write new ICC data
        my $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::ICC_Profile::Main');
        my %dirInfo = ( Parent => 'PNG', DirName => 'ICC_Profile' );
        my $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr);
        if (defined $buff and length $buff) {
            my $profileName = $et->GetNewValue($Image::ExifTool::PNG::Main{'iCCP-name'});
            $profileName = 'icm' unless defined $profileName;
            if (WriteProfile($outfile, \$profileName, \$buff)) {
                $et->VPrint(0, "Created ICC profile with name '${profileName}'\n");
                delete $$et{ADD_DIRS}{ICC_Profile}; # don't add it again
            }
        }
    }
    # must also add sRGB and gAMA before PLTE and IDAT
    if ($$et{ADD_PNG}) {
        my ($tag, %addBeforePLTE);
        foreach $tag (qw(sRGB gAMA)) {
            next unless $$et{ADD_PNG}{$tag};
            $addBeforePLTE{$tag} = $$et{ADD_PNG}{$tag};
            delete $$et{ADD_PNG}{$tag};
        }
        if (%addBeforePLTE) {
            my $save = $$et{ADD_PNG};
            $$et{ADD_PNG} = \%addBeforePLTE;
            AddChunks($et, $outfile);
            $$et{ADD_PNG} = $save;
        }
    }
    return 1;
}

#------------------------------------------------------------------------------
# This routine is called after we edit an existing directory
# Inputs: 0) ExifTool ref, 1) dir name, 2) output data ref
#         3) flag set if location is non-standard (to update, but not create from scratch)
# - on return, $$outBuff is set to '' if the directory is to be deleted
sub DoneDir($$$;$)
{
    my ($et, $dir, $outBuff, $nonStandard) = @_;
    my $saveDir = $dir;
    $dir = 'EXIF' if $dir eq 'IFD0';
    # don't add this directory again unless this is in a non-standard location
    if (not $nonStandard) {
        delete $$et{ADD_DIRS}{$dir};
        delete $$et{ADD_DIRS}{IFD0} if $dir eq 'EXIF';
    } elsif ($$et{DEL_GROUP}{$dir} or $$et{DEL_GROUP}{$saveDir}) {
        $et->VPrint(0,"  Deleting non-standard $dir\n");
        $$outBuff = '';
    }
}

#------------------------------------------------------------------------------
# Generate tEXt, zTXt or iTXt data for writing
# Inputs: 0) ExifTool ref, 1) tagID, 2) tagInfo ref, 3) value string, 4) language code
# Returns: chunk data (not including 8-byte chunk header)
# Notes: Sets ExifTool TextChunkType member to the type of chunk written
sub BuildTextChunk($$$$$)
{
    my ($et, $tag, $tagInfo, $val, $lang) = @_;
    my ($xtra, $compVal, $iTXt, $comp);
    if ($$tagInfo{SubDirectory}) {
        if ($$tagInfo{Name} eq 'XMP') {
            $iTXt = 2;      # write as iTXt but flag to avoid encoding
            # (never compress XMP)
        } else {
            $comp = 2;      # compress raw profile if possible
        }
    } else {
        # compress if specified
        $comp = 1 if $et->Options('Compress');
        if ($lang) {
            $iTXt = 1;      # write as iTXt if it has a language code
            $tag =~ s/-$lang$//;    # remove language code from tagID
        } elsif ($$et{OPTIONS}{Charset} ne 'Latin' and $val =~  /[\x80-\xff]/) {
            $iTXt = 1;      # write as iTXt if it contains non-Latin special characters
        } elsif ($$tagInfo{iTXt}) {
            $iTXt = 1;      # write as iTXt if specified in user-defined tag
        }
    }
    if ($comp) {
        my $warn;
        if (eval { require Compress::Zlib }) {
            my $deflate = Compress::Zlib::deflateInit();
            $compVal = $deflate->deflate($val) if $deflate;
            if (defined $compVal) {
                $compVal .= $deflate->flush();
                # only compress if it actually saves space
                unless (length($compVal) < length($val)) {
                    undef $compVal;
                    $warn = 'uncompressed data is smaller';
                }
            } else {
                $warn = 'deflate error';
            }
        } else {
            $warn = 'Compress::Zlib not available';
        }
        # warn if any user-specified compression fails
        if ($warn and $comp == 1) {
            $et->Warn("PNG:$$tagInfo{Name} not compressed ($warn)", 1);
        }
    }
    # decide whether to write as iTXt, zTXt or tEXt
    if ($iTXt) {
        $$et{TextChunkType} = 'iTXt';
        $xtra = (defined $compVal ? "\x01\0" : "\0\0") . ($lang || '') . "\0\0";
        # iTXt is encoded as UTF-8 (but note that XMP is already UTF-8)
        $val = $et->Encode($val, 'UTF8') if $iTXt == 1;
    } elsif (defined $compVal) {
        $$et{TextChunkType} = 'zTXt';
        $xtra = "\0";
    } else {
        $$et{TextChunkType} = 'tEXt';
        $xtra = '';
    }
    return $tag . "\0" . $xtra . (defined $compVal ? $compVal : $val);
}

#------------------------------------------------------------------------------
# Add any outstanding new chunks to the PNG image
# Inputs: 0) ExifTool object ref, 1) output file or scalar ref
#         2-N) dirs to add (empty to add all except EXIF 'IFD0', including PNG tags)
# Returns: true on success
sub AddChunks($$;@)
{
    my ($et, $outfile, @add) = @_;
    my ($addTags, $tag, $dir, $err, $tagTablePtr, $specified);

    if (@add) {
        $addTags = { }; # don't add any PNG tags
        $specified = 1;
    } else {
        $addTags = $$et{ADD_PNG};    # add all PNG tags...
        delete $$et{ADD_PNG};        # ...once
        # add all directories
        @add = sort keys %{$$et{ADD_DIRS}};
    }
    # write any outstanding PNG tags
    foreach $tag (sort keys %$addTags) {
        my $tagInfo = $$addTags{$tag};
        next if $$tagInfo{FakeTag}; # (iCCP-name)
        my $nvHash = $et->GetNewValueHash($tagInfo);
        # (native PNG information is always preferred, so don't rely on just IsCreating)
        next unless $$nvHash{IsCreating} or $et->IsOverwriting($nvHash) > 0;
        my $val = $et->GetNewValue($nvHash);
        if (defined $val) {
            next if $$nvHash{EditOnly};
            my $data;
            if ($$tagInfo{Table} eq \%Image::ExifTool::PNG::TextualData) {
                $data = BuildTextChunk($et, $tag, $tagInfo, $val, $$tagInfo{LangCode});
                $data = $$et{TextChunkType} . $data;
                delete $$et{TextChunkType};
            } else {
                $data = "$tag$val";
            }
            my $hdr = pack('N', length($data) - 4);
            my $cbuf = pack('N', CalculateCRC(\$data, undef));
            Write($outfile, $hdr, $data, $cbuf) or $err = 1;
            $et->VerboseValue("+ PNG:$$tagInfo{Name}", $val);
            ++$$et{CHANGED};
        }
    }
    # create any necessary directories
    foreach $dir (@add) {
        next unless $$et{ADD_DIRS}{$dir}; # make sure we want to add it first
        my $buff;
        my %dirInfo = (
            Parent => 'PNG',
            DirName => $dir,
        );
        if ($dir eq 'IFD0') {
            next unless $specified;     # wait until specifically asked to write EXIF 'IFD0'
            my $chunk = $stdCase{exif};
            # (zxIf was not adopted)
            #if ($et->Options('Compress')) {
            #    if (eval { require Compress::Zlib }) {
            #        $chunk = $stdCase{zxif};
            #    } else {
            #        $et->Warn("Creating uncompressed $stdCase{exif} chunk (Compress::Zlib not available)");
            #    }
            #}
            $et->VPrint(0, "Creating $chunk chunk:\n");
            $$et{TIFF_TYPE} = 'APP1';
            $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::Exif::Main');
            $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr, \&Image::ExifTool::WriteTIFF);
            if (defined $buff and length $buff) {
                WriteProfile($outfile, $chunk, \$buff) or $err = 1;
            }
        } elsif ($dir eq 'XMP') {
            $et->VPrint(0, "Creating XMP iTXt chunk:\n");
            $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::XMP::Main');
            $dirInfo{ReadOnly} = 1;
            $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr);
            if (defined $buff and length $buff and
                # the packet is read-only (because of CRC)
                Image::ExifTool::XMP::ValidateXMP(\$buff, 'r'))
            {
                # (previously, XMP was created as a non-standard XMP profile chunk)
                # $buff = $Image::ExifTool::xmpAPP1hdr . $buff;
                # WriteProfile($outfile, 'APP1', \$buff, 'generic') or $err = 1;
                # (but now write XMP iTXt chunk according to XMP specification)
                $buff = "iTXtXML:com.adobe.xmp\0\0\0\0\0" . $buff;
                my $hdr = pack('N', length($buff) - 4);
                my $cbuf = pack('N', CalculateCRC(\$buff, undef));
                Write($outfile, $hdr, $buff, $cbuf) or $err = 1;
            }
        } elsif ($dir eq 'IPTC') {
            $et->Warn('Creating non-standard IPTC in PNG', 1);
            $et->VPrint(0, "Creating IPTC profile:\n");
            # write new IPTC data (stored in a Photoshop directory)
            $dirInfo{DirName} = 'Photoshop';
            $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::Photoshop::Main');
            $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr);
            if (defined $buff and length $buff) {
                WriteProfile($outfile, 'iptc', \$buff, 'IPTC') or $err = 1;
            }
        } elsif ($dir eq 'ICC_Profile') {
            $et->VPrint(0, "Creating ICC profile:\n");
            # write new ICC data (only done if we couldn't create iCCP chunk)
            $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::ICC_Profile::Main');
            $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr);
            if (defined $buff and length $buff) {
                WriteProfile($outfile, 'icm', \$buff, 'ICC') or $err = 1;
                $et->Warn('Wrote ICC as a raw profile (no Compress::Zlib)');
            }
        } elsif ($dir eq 'PNG-pHYs') {
            $et->VPrint(0, "Creating pHYs chunk (default 2834 pixels per meter):\n");
            $tagTablePtr = Image::ExifTool::GetTagTable('Image::ExifTool::PNG::PhysicalPixel');
            my $blank = "\0\0\x0b\x12\0\0\x0b\x12\x01"; # 2834 pixels per meter (72 dpi)
            $dirInfo{DataPt} = \$blank;
            $buff = $et->WriteDirectory(\%dirInfo, $tagTablePtr);
            if (defined $buff and length $buff) {
                $buff = 'pHYs' . $buff; # CRC includes chunk name
                my $hdr = pack('N', length($buff) - 4);
                my $cbuf = pack('N', CalculateCRC(\$buff, undef));
                Write($outfile, $hdr, $buff, $cbuf) or $err = 1;
            }
        } else {
            next;
        }
        delete $$et{ADD_DIRS}{$dir};  # don't add again
    }
    return not $err;
}


1; # end

__END__

=head1 NAME

Image::ExifTool::WritePNG.pl - Write PNG meta information

=head1 SYNOPSIS

These routines are autoloaded by Image::ExifTool::PNG.

=head1 DESCRIPTION

This file contains routines to write PNG metadata.

=head1 NOTES

Compress::Zlib is required to write compressed text.

Existing text tags are always rewritten in their original form (compressed
zTXt, uncompressed tEXt or international iTXt), so pre-existing compressed
information can only be modified if Compress::Zlib is available.

Newly created textual information is written in uncompressed tEXt form by
default, or as compressed zTXt if the Compress option is used and
Compress::Zlib is available (but only if the resulting compressed data is
smaller than the original text, which isn't always the case for short text
strings).

=head1 AUTHOR

Copyright 2003-2026, 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 SEE ALSO

L<Image::ExifTool::PNG(3pm)|Image::ExifTool::PNG>,
L<Image::ExifTool(3pm)|Image::ExifTool>

=cut
