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PNG re-work: expand the pngdump.pl tool a bit

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1 parent 8cf4109 commit 2d78f29c929ed38a0e00e19012f1568963ebecd2 @tonycoz committed Apr 9, 2012
Showing with 135 additions and 5 deletions.
  1. +135 −5 fileformatdocs/pngdump.pl
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140 fileformatdocs/pngdump.pl
@@ -1,5 +1,10 @@
#!perl
use strict;
+use IO::Uncompress::Inflate qw(inflate);
+use Getopt::Long;
+
+my $dumpall = 0;
+GetOptions(dumpall => \$dumpall);
my $file = shift
or die "Usage: $0 filename\n";
@@ -25,10 +30,13 @@
while (my ($dlen, $data, $len, $type, $payload, $crc) = read_chunk($fh)) {
dump_data($offset, $data);
$offset += $dlen;
+ my $calc_crc = crc($type . $payload);
+ my $src_crc = unpack("N", $crc);
$type =~ s/([^ -\x7f])/sprintf("\\x%02x", ord $1)/ge;
print " Type: $type\n";
print " Length: $len\n";
+ printf " CRC: %x (calculated: %x)\n", $src_crc, $calc_crc;
if ($type eq 'IHDR') {
my ($w, $h, $d, $ct, $comp, $filter, $inter) =
unpack("NNCCCCC", $payload);
@@ -38,7 +46,7 @@
Depth: $d
Colour type: $ct
Filter: $filter
- Interpolation: $inter
+ Interlace: $inter
EOS
$colour_type = $ct;
}
@@ -82,11 +90,39 @@
Unit: $unit ($unitname)
EOS
}
+ elsif ($type eq 'tEXt') {
+ my ($key, $value) = split /\0/, $payload, 2;
+ print <<EOS;
+ Keyword: $key
+ Value: $value
+EOS
+ do_more_text($key, $value);
+ }
+ elsif ($type eq 'zTXt') {
+ my ($key, $rest) = split /\0/, $payload, 2;
+ my $ctype = ord $rest;
+ my $ztxt = substr($rest, 1);
+ my $value = do_inflate($ztxt);
+ print <<EOS;
+ Keyword: $key
+ Value: $value
+EOS
+ do_more_text($key, $value);
+ }
$type eq "IEND"
and last;
}
+sub do_more_text {
+ my ($key, $text) = @_;
+
+ if ($key eq 'Raw profile type xmp'
+ && $text =~ s/^\s*xmp\s+\d+\s+//) {
+ print " XMP: ", pack("H*", join('', split ' ', $text)), "\n";
+ }
+}
+
sub read_chunk {
my ($fh) = @_;
@@ -112,11 +148,105 @@ sub read_chunk {
sub dump_data {
my ($offset, $data) = @_;
- printf("%08x: ", $offset);
- if (length $data > 20) {
- print unpack("H*", substr($data, 0, 18)), "...\n";
+ if (length $data > 28) {
+ if ($dumpall) {
+ for my $i (0 .. int((15 + length $data) / 16) - 1) {
+ my $row = substr($data, $i * 16, 16);
+ (my $clean = $row) =~ tr/ -~/./c;
+ printf("%08x: %-32s %s\n", $offset, unpack("H*", $row), $clean);
+ }
+ }
+ else {
+ printf "%08x: %s...\n", $offset, unpack("H*", substr($data, 0, 26));
+ }
}
else {
- print unpack("H*", $data), "\n";
+ printf "%08x: %s\n", $offset, unpack("H*", $data), "\n";
}
}
+
+#unsigned long crc_table[256];
+my @crc_table;
+
+#/* Flag: has the table been computed? Initially false. */
+# int crc_table_computed = 0;
+
+# /* Make the table for a fast CRC. */
+# void make_crc_table(void)
+# {
+sub make_crc_table {
+# unsigned long c;
+# int n, k;
+#
+# for (n = 0; n < 256; n++) {
+ for my $n (0 .. 255) {
+# c = (unsigned long) n;
+ my $c = $n;
+# for (k = 0; k < 8; k++) {
+ for my $k (0 .. 7) {
+# if (c & 1)
+# c = 0xedb88320L ^ (c >> 1);
+# else
+# c = c >> 1;
+ if ($c & 1) {
+ $c = 0xedb88320 ^ ($c >> 1);
+ }
+ else {
+ $c = $c >> 1;
+ }
+# }
+ }
+# crc_table[n] = c;
+ $crc_table[$n] = $c;
+# }
+ }
+# crc_table_computed = 1;
+# }
+}
+
+# /* Update a running CRC with the bytes buf[0..len-1]--the CRC
+# should be initialized to all 1's, and the transmitted value
+# is the 1's complement of the final running CRC (see the
+# crc() routine below). */
+
+# unsigned long update_crc(unsigned long crc, unsigned char *buf,
+# int len)
+# {
+sub update_crc {
+ my ($crc, $data) = @_;
+# unsigned long c = crc;
+# int n;
+
+# if (!crc_table_computed)
+# make_crc_table();
+ @crc_table or make_crc_table();
+# for (n = 0; n < len; n++) {
+# c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
+# }
+ for my $code (unpack("C*", $data)) {
+ $crc = $crc_table[($crc ^ $code) & 0xFF] ^ ($crc >> 8);
+ }
+# return c;
+# }
+ return $crc;
+}
+
+# /* Return the CRC of the bytes buf[0..len-1]. */
+# unsigned long crc(unsigned char *buf, int len)
+# {
+# return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
+# }
+
+sub crc {
+ my $data = shift;
+
+ return update_crc(0xFFFFFFFF, $data) ^ 0xFFFFFFFF;
+}
+
+sub do_inflate {
+ my $z = shift;
+ my $out = '';
+ inflate(\$z, \$out);
+
+ return $out;
+}

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