source: main/trunk/greenstone2/perllib/cpan/Image/ExifTool/BZZ.pm@ 24107

Last change on this file since 24107 was 24107, checked in by sjm84, 13 years ago

Updating the ExifTool perl modules
  • Property svn:executable set to *
File size: 17.5 KB
Line 
1#------------------------------------------------------------------------------
2# File: BZZ.pm
3#
4# Description: Utility to decode BZZ compressed data
5#
6# Revisions: 09/22/2008 - P. Harvey Created
7#
8# References: 1) http://djvu.sourceforge.net/
9# 2) http://www.djvu.org/
10#
11# Notes: This code based on ZPCodec and BSByteStream of DjVuLibre 3.5.21
12# (see NOTES documentation below for license/copyright details)
13#------------------------------------------------------------------------------
14
15package Image::ExifTool::BZZ;
16
17use strict;
18use integer; # IMPORTANT!! use integer arithmetic throughout
19require Exporter;
20use vars qw($VERSION @ISA @EXPORT_OK);
21
22$VERSION = '1.00';
23@ISA = qw(Exporter);
24@EXPORT_OK = qw(Decode);
25
26# constants
27sub FREQMAX { 4 }
28sub CTXIDS { 3 }
29sub MAXBLOCK { 4096 }
30
31# This table has been designed for the ZPCoder
32# by running the following command in file 'zptable.sn':
33# (fast-crude (steady-mat 0.0035 0.0002) 260)))
34my @default_ztable_p = (
35 0x8000, 0x8000, 0x8000, 0x6bbd, 0x6bbd, 0x5d45, 0x5d45, 0x51b9, 0x51b9, 0x4813,
36 0x4813, 0x3fd5, 0x3fd5, 0x38b1, 0x38b1, 0x3275, 0x3275, 0x2cfd, 0x2cfd, 0x2825,
37 0x2825, 0x23ab, 0x23ab, 0x1f87, 0x1f87, 0x1bbb, 0x1bbb, 0x1845, 0x1845, 0x1523,
38 0x1523, 0x1253, 0x1253, 0x0fcf, 0x0fcf, 0x0d95, 0x0d95, 0x0b9d, 0x0b9d, 0x09e3,
39 0x09e3, 0x0861, 0x0861, 0x0711, 0x0711, 0x05f1, 0x05f1, 0x04f9, 0x04f9, 0x0425,
40 0x0425, 0x0371, 0x0371, 0x02d9, 0x02d9, 0x0259, 0x0259, 0x01ed, 0x01ed, 0x0193,
41 0x0193, 0x0149, 0x0149, 0x010b, 0x010b, 0x00d5, 0x00d5, 0x00a5, 0x00a5, 0x007b,
42 0x007b, 0x0057, 0x0057, 0x003b, 0x003b, 0x0023, 0x0023, 0x0013, 0x0013, 0x0007,
43 0x0007, 0x0001, 0x0001, 0x5695, 0x24ee, 0x8000, 0x0d30, 0x481a, 0x0481, 0x3579,
44 0x017a, 0x24ef, 0x007b, 0x1978, 0x0028, 0x10ca, 0x000d, 0x0b5d, 0x0034, 0x078a,
45 0x00a0, 0x050f, 0x0117, 0x0358, 0x01ea, 0x0234, 0x0144, 0x0173, 0x0234, 0x00f5,
46 0x0353, 0x00a1, 0x05c5, 0x011a, 0x03cf, 0x01aa, 0x0285, 0x0286, 0x01ab, 0x03d3,
47 0x011a, 0x05c5, 0x00ba, 0x08ad, 0x007a, 0x0ccc, 0x01eb, 0x1302, 0x02e6, 0x1b81,
48 0x045e, 0x24ef, 0x0690, 0x2865, 0x09de, 0x3987, 0x0dc8, 0x2c99, 0x10ca, 0x3b5f,
49 0x0b5d, 0x5695, 0x078a, 0x8000, 0x050f, 0x24ee, 0x0358, 0x0d30, 0x0234, 0x0481,
50 0x0173, 0x017a, 0x00f5, 0x007b, 0x00a1, 0x0028, 0x011a, 0x000d, 0x01aa, 0x0034,
51 0x0286, 0x00a0, 0x03d3, 0x0117, 0x05c5, 0x01ea, 0x08ad, 0x0144, 0x0ccc, 0x0234,
52 0x1302, 0x0353, 0x1b81, 0x05c5, 0x24ef, 0x03cf, 0x2b74, 0x0285, 0x201d, 0x01ab,
53 0x1715, 0x011a, 0x0fb7, 0x00ba, 0x0a67, 0x01eb, 0x06e7, 0x02e6, 0x0496, 0x045e,
54 0x030d, 0x0690, 0x0206, 0x09de, 0x0155, 0x0dc8, 0x00e1, 0x2b74, 0x0094, 0x201d,
55 0x0188, 0x1715, 0x0252, 0x0fb7, 0x0383, 0x0a67, 0x0547, 0x06e7, 0x07e2, 0x0496,
56 0x0bc0, 0x030d, 0x1178, 0x0206, 0x19da, 0x0155, 0x24ef, 0x00e1, 0x320e, 0x0094,
57 0x432a, 0x0188, 0x447d, 0x0252, 0x5ece, 0x0383, 0x8000, 0x0547, 0x481a, 0x07e2,
58 0x3579, 0x0bc0, 0x24ef, 0x1178, 0x1978, 0x19da, 0x2865, 0x24ef, 0x3987, 0x320e,
59 0x2c99, 0x432a, 0x3b5f, 0x447d, 0x5695, 0x5ece, 0x8000, 0x8000, 0x5695, 0x481a,
60 0x481a, 0, 0, 0, 0, 0
61);
62my @default_ztable_m = (
63 0x0000, 0x0000, 0x0000, 0x10a5, 0x10a5, 0x1f28, 0x1f28, 0x2bd3, 0x2bd3, 0x36e3,
64 0x36e3, 0x408c, 0x408c, 0x48fd, 0x48fd, 0x505d, 0x505d, 0x56d0, 0x56d0, 0x5c71,
65 0x5c71, 0x615b, 0x615b, 0x65a5, 0x65a5, 0x6962, 0x6962, 0x6ca2, 0x6ca2, 0x6f74,
66 0x6f74, 0x71e6, 0x71e6, 0x7404, 0x7404, 0x75d6, 0x75d6, 0x7768, 0x7768, 0x78c2,
67 0x78c2, 0x79ea, 0x79ea, 0x7ae7, 0x7ae7, 0x7bbe, 0x7bbe, 0x7c75, 0x7c75, 0x7d0f,
68 0x7d0f, 0x7d91, 0x7d91, 0x7dfe, 0x7dfe, 0x7e5a, 0x7e5a, 0x7ea6, 0x7ea6, 0x7ee6,
69 0x7ee6, 0x7f1a, 0x7f1a, 0x7f45, 0x7f45, 0x7f6b, 0x7f6b, 0x7f8d, 0x7f8d, 0x7faa,
70 0x7faa, 0x7fc3, 0x7fc3, 0x7fd7, 0x7fd7, 0x7fe7, 0x7fe7, 0x7ff2, 0x7ff2, 0x7ffa,
71 0x7ffa, 0x7fff, 0x7fff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
72 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
73 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
74 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
75 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
76 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
77 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
78);
79my @default_ztable_up = (
80 84, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
81 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
82 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
83 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65,
84 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81,
85 82, 81, 82, 9, 86, 5, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97,
86 82, 99, 76, 101, 70, 103, 66, 105, 106, 107, 66, 109, 60, 111, 56, 69,
87 114, 65, 116, 61, 118, 57, 120, 53, 122, 49, 124, 43, 72, 39, 60, 33,
88 56, 29, 52, 23, 48, 23, 42, 137, 38, 21, 140, 15, 142, 9, 144, 141,
89 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 70, 157, 66, 81, 62, 75,
90 58, 69, 54, 65, 50, 167, 44, 65, 40, 59, 34, 55, 30, 175, 24, 177,
91 178, 179, 180, 181, 182, 183, 184, 69, 186, 59, 188, 55, 190, 51, 192, 47,
92 194, 41, 196, 37, 198, 199, 72, 201, 62, 203, 58, 205, 54, 207, 50, 209,
93 46, 211, 40, 213, 36, 215, 30, 217, 26, 219, 20, 71, 14, 61, 14, 57,
94 8, 53, 228, 49, 230, 45, 232, 39, 234, 35, 138, 29, 24, 25, 240, 19,
95 22, 13, 16, 13, 10, 7, 244, 249, 10, 89, 230, 0, 0, 0, 0, 0
96);
97my @default_ztable_dn = (
98 145, 4, 3, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
99 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29,
100 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,
101 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61,
102 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77,
103 78, 79, 80, 85, 226, 6, 176, 143, 138, 141, 112, 135, 104, 133, 100, 129,
104 98, 127, 72, 125, 102, 123, 60, 121, 110, 119, 108, 117, 54, 115, 48, 113,
105 134, 59, 132, 55, 130, 51, 128, 47, 126, 41, 62, 37, 66, 31, 54, 25,
106 50, 131, 46, 17, 40, 15, 136, 7, 32, 139, 172, 9, 170, 85, 168, 248,
107 166, 247, 164, 197, 162, 95, 160, 173, 158, 165, 156, 161, 60, 159, 56, 71,
108 52, 163, 48, 59, 42, 171, 38, 169, 32, 53, 26, 47, 174, 193, 18, 191,
109 222, 189, 218, 187, 216, 185, 214, 61, 212, 53, 210, 49, 208, 45, 206, 39,
110 204, 195, 202, 31, 200, 243, 64, 239, 56, 237, 52, 235, 48, 233, 44, 231,
111 38, 229, 34, 227, 28, 225, 22, 223, 16, 221, 220, 63, 8, 55, 224, 51,
112 2, 47, 87, 43, 246, 37, 244, 33, 238, 27, 236, 21, 16, 15, 8, 241,
113 242, 7, 10, 245, 2, 1, 83, 250, 2, 143, 246, 0, 0, 0, 0, 0
114);
115
116#------------------------------------------------------------------------------
117# New - create new BZZ object
118# Inputs: 0) reference to BZZ object or BZZ class name
119# Returns: blessed BZZ object ref
120sub new
121{
122 local $_;
123 my $that = shift;
124 my $class = ref($that) || $that || 'Image::ExifTool::BZZ';
125 return bless {}, $class;
126}
127
128#------------------------------------------------------------------------------
129# Initialize BZZ object
130# Inputs: 0) BZZ object ref, 1) data ref, 2) true for DjVu compatibility
131sub Init($$)
132{
133 my ($self, $dataPt, $djvucompat) = @_;
134 # Create machine independent ffz table
135 my $ffzt = $$self{ffzt} = [ ];
136 my ($i, $j);
137 for ($i=0; $i<256; $i++) {
138 $$ffzt[$i] = 0;
139 for ($j=$i; $j&0x80; $j<<=1) {
140 $$ffzt[$i] += 1;
141 }
142 }
143 # Initialize table
144 $$self{p} = [ @default_ztable_p ];
145 $$self{'m'} = [ @default_ztable_m ];
146 $$self{up} = [ @default_ztable_up ];
147 $$self{dn} = [ @default_ztable_dn ];
148 # Patch table (and lose DjVu compatibility)
149 unless ($djvucompat) {
150 my ($p, $m, $dn) = ($$self{p}, $$self{'m'}, $$self{dn});
151 for ($j=0; $j<256; $j++) {
152 my $a = (0x10000 - $$p[$j]) & 0xffff;
153 while ($a >= 0x8000) { $a = ($a<<1) & 0xffff }
154 if ($$m[$j]>0 && $a+$$p[$j]>=0x8000 && $a>=$$m[$j]) {
155 $$dn[$j] = $default_ztable_dn[$default_ztable_dn[$j]];
156 }
157 }
158 }
159 $$self{ctx} = [ (0) x 300 ];
160 $$self{DataPt} = $dataPt;
161 $$self{Pos} = 0;
162 $$self{DataLen} = length $$dataPt;
163 $$self{a} = 0;
164 $$self{buffer} = 0;
165 $$self{fence} = 0;
166 $$self{blocksize} = 0;
167 # Read first 16 bits of code
168 if (length($$dataPt) >= 2) {
169 $$self{code} = unpack('n', $$dataPt);
170 $$self{Pos} += 2;
171 } elsif (length($$dataPt) >= 1) {
172 $$self{code} = (unpack('C', $$dataPt) << 8) | 0xff;
173 $$self{Pos}++;
174 } else {
175 $$self{code} = 0xffff;
176 }
177 $$self{byte} = $$self{code} & 0xff;
178 # Preload buffer
179 $$self{delay} = 25;
180 $$self{scount} = 0;
181 # Compute initial fence
182 $$self{fence} = $$self{code} >= 0x8000 ? 0x7fff : $$self{code};
183}
184
185#------------------------------------------------------------------------------
186# Decode data block
187# Inputs: 0) optional BZZ object ref, 1) optional data ref
188# Returns: decoded data or undefined on error
189# Notes: If called without a data ref, an input BZZ object ref must be given and
190# the BZZ object must have been initialized by a previous call to Init()
191sub Decode($;$)
192{
193 # Decode input stream
194 local $_;
195 my $self;
196 if (ref $_[0] and UNIVERSAL::isa($_[0],'Image::ExifTool::BZZ')) {
197 $self = shift;
198 } else {
199 $self = new Image::ExifTool::BZZ;
200 }
201 my $dataPt = shift;
202 if ($dataPt) {
203 $self->Init($dataPt, 1);
204 } else {
205 $dataPt = $$self{DataPt} or return undef;
206 }
207 # Decode block size
208 my $n = 1;
209 my $m = (1 << 24);
210 while ($n < $m) {
211 my $b = $self->decode_sub(0x8000 + ($$self{a}>>1));
212 $n = ($n<<1) | $b;
213 }
214 $$self{size} = $n - $m;
215
216 return '' unless $$self{size};
217 return undef if $$self{size} > MAXBLOCK()*1024;
218 # Allocate
219 if ($$self{blocksize} < $$self{size}) {
220 $$self{blocksize} = $$self{size};
221 }
222 # Decode Estimation Speed
223 my $fshift = 0;
224 if ($self->decode_sub(0x8000 + ($$self{a}>>1))) {
225 $fshift += 1;
226 $fshift += 1 if $self->decode_sub(0x8000 + ($$self{a}>>1));
227 }
228 # Prepare Quasi MTF
229 my @mtf = (0..255);
230 my @freq = (0) x FREQMAX();
231 my $fadd = 4;
232 # Decode
233 my $mtfno = 3;
234 my $markerpos = -1;
235 my $cx = $$self{ctx};
236 my ($i, @dat);
237byte: for ($i=0; $i<$$self{size}; $i++) {
238 # dummy loop avoids use of "goto" statement
239dummy: for (;;) {
240 my $ctxid = CTXIDS() - 1;
241 $ctxid = $mtfno if $ctxid > $mtfno;
242 my $cp = 0;
243 my ($imtf, $bits);
244 for ($imtf=0; $imtf<2; ++$imtf) {
245 if ($self->decoder($$cx[$cp+$ctxid])) {
246 $mtfno = $imtf;
247 $dat[$i] = $mtf[$mtfno];
248 # (a "goto" here could give a segfault due to a Perl bug)
249 last dummy; # do rotation
250 }
251 $cp += CTXIDS();
252 }
253 for ($bits=1; $bits<8; ++$bits, $imtf<<=1) {
254 if ($self->decoder($$cx[$cp])) {
255 my $n = 1;
256 my $m = (1 << $bits);
257 while ($n < $m) {
258 my $b = $self->decoder($$cx[$cp+$n]);
259 $n = ($n<<1) | $b;
260 }
261 $mtfno = $imtf + $n - $m;
262 $dat[$i] = $mtf[$mtfno];
263 last dummy; # do rotation
264 }
265 $cp += $imtf;
266 }
267 $mtfno=256;
268 $dat[$i] = 0;
269 $markerpos=$i;
270 next byte; # no rotation necessary
271 }
272 # Rotate mtf according to empirical frequencies (new!)
273 # Adjust frequencies for overflow
274 $fadd = $fadd + ($fadd >> $fshift);
275 if ($fadd > 0x10000000) {
276 $fadd >>= 24;
277 $_ >>= 24 foreach @freq;
278 }
279 # Relocate new char according to new freq
280 my $fc = $fadd;
281 $fc += $freq[$mtfno] if $mtfno < FREQMAX();
282 my $k;
283 for ($k=$mtfno; $k>=FREQMAX(); $k--) {
284 $mtf[$k] = $mtf[$k-1];
285 }
286 for (; $k>0 && $fc>=$freq[$k-1]; $k--) {
287 $mtf[$k] = $mtf[$k-1];
288 $freq[$k] = $freq[$k-1];
289 }
290 $mtf[$k] = $dat[$i];
291 $freq[$k] = $fc;
292 # when "goto" was used, Perl 5.8.6 could segfault here
293 # unless "next" was explicitly stated
294 }
295#
296# Reconstruct the string
297#
298 return undef if $markerpos<1 || $markerpos>=$$self{size};
299 # Allocate pointers
300 # Prepare count buffer
301 my @count = (0) x 256;
302 my @posn;
303 # Fill count buffer
304 no integer;
305 for ($i=0; $i<$markerpos; $i++) {
306 my $c = $dat[$i];
307 $posn[$i] = ($c<<24) | ($count[$c]++ & 0xffffff);
308 }
309 $posn[$i++] = 0; # (initialize marker entry just to be safe)
310 for ( ; $i<$$self{size}; $i++) {
311 my $c = $dat[$i];
312 $posn[$i] = ($c<<24) | ($count[$c]++ & 0xffffff);
313 }
314 use integer;
315 # Compute sorted char positions
316 my $last = 1;
317 for ($i=0; $i<256; $i++) {
318 my $tmp = $count[$i];
319 $count[$i] = $last;
320 $last += $tmp;
321 }
322 # Undo the sort transform
323 $i = 0;
324 $last = $$self{size}-1;
325 while ($last > 0) {
326 my $n = $posn[$i];
327 no integer;
328 my $c = $n >> 24;
329 use integer;
330 $dat[--$last] = $c;
331 $i = $count[$c] + ($n & 0xffffff);
332 }
333 # Final check and return decoded data
334 return undef if $i != $markerpos;
335 pop @dat; # (last byte isn't real)
336 return pack 'C*', @dat;
337}
338
339#------------------------------------------------------------------------------
340# Inputs: 0) BZZ object ref, 1) ctx
341# Returns: decoded bit
342sub decoder($$)
343{
344 my ($self, $ctx) = @_;
345 my $z = $$self{a} + $self->{p}[$ctx];
346 if ($z <= $$self{fence}) {
347 $$self{a} = $z;
348 return ($ctx & 1);
349 }
350 # must pass $_[1] so subroutine can modify value (darned C++ pass-by-reference!)
351 return $self->decode_sub($z, $_[1]);
352}
353
354#------------------------------------------------------------------------------
355# Inputs: 0) BZZ object ref, 1) z, 2) ctx (or undef)
356# Returns: decoded bit
357sub decode_sub($$;$)
358{
359 my ($self, $z, $ctx) = @_;
360
361 # ensure that we have at least 16 bits of encoded data available
362 if ($$self{scount} < 16) {
363 # preload byte by byte until we have at least 24 bits
364 while ($$self{scount} <= 24) {
365 if ($$self{Pos} < $$self{DataLen}) {
366 $$self{byte} = ord(substr(${$$self{DataPt}}, $$self{Pos}, 1));
367 ++$$self{Pos};
368 } else {
369 $$self{byte} = 0xff;
370 if (--$$self{delay} < 1) {
371 # setting size to zero forces error return from Decode()
372 $$self{size} = 0;
373 return 0;
374 }
375 }
376 $$self{buffer} = ($$self{buffer}<<8) | $$self{byte};
377 $$self{scount} += 8;
378 }
379 }
380 # Save bit
381 my $a = $$self{a};
382 my ($bit, $code);
383 if (defined $ctx) {
384 $bit = ($ctx & 1);
385 # Avoid interval reversion
386 my $d = 0x6000 + (($z+$a)>>2);
387 $z = $d if $z > $d;
388 } else {
389 $bit = 0;
390 }
391 # Test MPS/LPS
392 if ($z > ($code = $$self{code})) {
393 $bit ^= 1;
394 # LPS branch
395 $z = 0x10000 - $z;
396 $a += $z;
397 $code += $z;
398 # LPS adaptation
399 $_[2] = $self->{dn}[$ctx] if defined $ctx;
400 # LPS renormalization
401 my $sft = $a>=0xff00 ? $self->{ffzt}[$a&0xff] + 8 : $self->{ffzt}[($a>>8)&0xff];
402 $$self{scount} -= $sft;
403 $$self{a} = ($a<<$sft) & 0xffff;
404 $code = (($code<<$sft) & 0xffff) | (($$self{buffer}>>$$self{scount}) & ((1<<$sft)-1));
405 } else {
406 # MPS adaptation
407 $_[2] = $self->{up}[$ctx] if defined $ctx and $a >= $self->{'m'}[$ctx];
408 # MPS renormalization
409 $$self{scount} -= 1;
410 $$self{a} = ($z<<1) & 0xffff;
411 $code = (($code<<1) & 0xffff) | (($$self{buffer}>>$$self{scount}) & 1);
412 }
413 # Adjust fence and save new code
414 $$self{fence} = $code >= 0x8000 ? 0x7fff : $code;
415 $$self{code} = $code;
416 return $bit;
417}
418
4191; # end
420
421__END__
422
423=head1 NAME
424
425Image::ExifTool::BZZ - Utility to decode BZZ compressed data
426
427=head1 SYNOPSIS
428
429This module is used by Image::ExifTool
430
431=head1 DESCRIPTION
432
433This module contains definitions required by Image::ExifTool to decode BZZ
434compressed data in DjVu images.
435
436=head1 NOTES
437
438This code is based on ZPCodec and BSByteStream of DjVuLibre 3.5.21 (see
439additional copyrights and the first reference below), which are covered
440under the GNU GPL license.
441
442This is implemented as Image::ExifTool::BZZ instead of Compress::BZZ because
443I am hoping that someone else will write a proper Compress::BZZ module (with
444compression ability).
445
446=head1 AUTHOR
447
448Copyright 2003-2011, Phil Harvey (phil at owl.phy.queensu.ca)
449Copyright 2002, Leon Bottou and Yann Le Cun
450Copyright 2001, AT&T
451Copyright 1999-2001, LizardTech Inc.
452
453This library is free software; you can redistribute it and/or modify it
454under the same terms as Perl itself.
455
456=head1 REFERENCES
457
458=over 4
459
460=item L<http://djvu.sourceforge.net/>
461
462=item L<http://www.djvu.org/>
463
464=back
465
466=head1 SEE ALSO
467
468L<Image::ExifTool::DjVu(3pm)|Image::ExifTool::DjVu>,
469L<Image::ExifTool(3pm)|Image::ExifTool>
470
471=cut
472
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