Images 01/29/04 Resources: Yale Web Style Guide The GIF Controversy Unisys - lzw.
LZW Encoding
38
Robert Sedgewick and Kevin Wayne • Copyright © 2005 • http://www.Princeton.EDU/~cos226 LZW Encoding The input message was taken from: http://www-mtl.mit.edu/Courses/6.095/notes/LZW- examples.html
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LZW Encoding. The input message was taken from: http://www-mtl.mit.edu/Courses/6.095/notes/LZW-examples.html. Input. Send. LZW Encoding. SEND. 256. i. 105. t. 116. Dictionary. t. 116. Index. Word. Index. Word. y. 121. 0. 258. it. _. 32. …. 259. tt. b. 98. i. 32. _. - PowerPoint PPT Presentation
Transcript of LZW Encoding
Robert Sedgewick and Kevin Wayne • Copyright © 2005 • http://www.Princeton.EDU/~cos226
LZW Encoding
The input message was taken from:http://www-mtl.mit.edu/Courses/6.095/notes/LZW-examples.html
2
LZW Encoding
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LZW Encoding
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Dictionary
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Send
116
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98
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Input
t
t
y
_
b
t
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b
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LZW Encoding
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STOP257
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it
Word
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Index
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itt264
Dictionary
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Send
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Input
t
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b
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Input
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LZW Encoding
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Index
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itt264
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Send
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Input
t
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b
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258t
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itt
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LZW Encoding
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SEND
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STOP257
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it
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Index
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itt264
Dictionary
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Send
116
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Input
t
t
y
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b
t
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_
262b
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258t
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_
266
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110n
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ty_
12
LZW Encoding
Word
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a
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Index
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32
…
97
98
122
SEND
…
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STOP257
…
it
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tt
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_b
bi
ty_
_bi
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_bin
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Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
_bi
13
LZW Encoding
Word
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a
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Index
…
32
…
97
98
122
SEND
…
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STOP257
…
it
Word
tt
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_b
bi
ty_
_bi
it_
_bin
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Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
it_
14
LZW Encoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
_bin
15
LZW Encoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
16
LZW Encoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
17
105
Send
116
116
121
32
98
258
260
i
Input
t
t
y
_
b
t
t
y
_
262b
i
258t
i
_
266
b
i
110n
257STOP
256SEND
LZW Encoding
Words
Original
Message
18
Compression Achieved
Bits / word
8
Total
144
LZW message 14 9 126
Robert Sedgewick and Kevin Wayne • Copyright © 2005 • http://www.Princeton.EDU/~cos226
LZW Decoding
19
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
20
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
21
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
22
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
23
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
24
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
25
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
26
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
27
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
28
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
29
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
30
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
31
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
32
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
33
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
34
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
35
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
36
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
37
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
38
LZW Decoding
Word
_
a
b
z
0
Index
…
32
…
97
98
122
SEND
…
256
STOP257
…
it
Word
tt
ty
y_
_b
bi
ty_
_bi
it_
_bin
258
Index
259
260
261
262
263
265
266
267
268
itt264
Dictionary
105
Received
116
116
121
32
98
260
262
i
Input
t
t
y
_
b
t
t
y
_
258
b
i
t
258 i
266 _
b
i
110 n
257 STOP
256 SEND
