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Compressing

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Data Compression (LZW Methode)
فشرده سازی با شرح مختصری بر LZW

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Compressing

1. 1. LZW 1
2. 2. StatisticalDictionary Based RLE Methods LZW 2
3. 3. 3
4. 4. –       4
5. 5.     56KBPS  5
6. 6.     6
7. 7.   codingInterpixlepsychovisual 7
8. 8.   Style  Lossy Lossless Lossy   Lossless  8
9. 9. Run Length Encoding  nd n d  Lossless     Hello. How are you? H1e1l2o1.1_1H1o1w1_1a1r1e1_1y1o1u1?1   9
10. 10.     Lossless     10
11. 11.   11
12. 12.  Token     Lossless LZW   12
13. 13. 13
14. 14. LZ77 LZ78 LZJ LZFGLZR LZW LZSS LZH LZB LZC LZT LZMW ZIP  PNG LZ  Huffman Coding LZ77 ZIP Deflate 14
15. 15. LZ78 Terry Welch            15
16. 16. W = NIL; STARTwhile (there is input) W= NULL{ K = next symbol from input; YE IS EOF S STOP if (WK exists in the dictionary) ? NO { K=NEXT INPUT W = WK; } YE else W=WK S IS WK FOUND { ? output (index(W)); NO add WK to the OUTPUT INDEX OF W dictionary; ADD WK TO DICTIONARY W = K; } W=K} 16
17. 17.  a b d a b d a cb a  d c  a 1 b 2 c 3 d 4 17
18. 18.  W = Null a b d a b d a cK = a WK = a K  a 1 b 2 c 3 d 4 18
19. 19.  K = b. a b d a b d a c WK = ab K  WK  1  a 1 ab 5 Set W = b b 2 c 3 d 4 19
20. 20. K = d a b d a b d a c WK = bd K  Bd  1 2 Output code b a 1 ab 5 Set W = d b 2 bd 6 c 3 d 4 20
21. 21. LZWK = a a b d a b d a c WK = da K   1 2 4 Output code d a 1 ab 5 Set W = a b 2 bd 6 c 3 da 7 d 4 21
22. 22. LZWK = b a b d a b d a c WK = ab K  1 2 4 a 1 ab 5 b 2 bd 6 c 3 da 7 d 4 22
23. 23. LZWK = d a b d a b d a c WK = abd K  1 2 4 5 W a 1 ab 5 Output code for W. b 2 bd 6 Set W = d c 3 da 7 d 4 ab 8 d 23
24. 24. LZWK = a a b d a b d a c WK = da K  1 2 4 5 a 1 ab 5 b 2 bd 6 c 3 da 7 d 4 ab 8 d 24
25. 25. LZWK = c a b d a b d a c WK = dac K  1 2 4 5 7 WK  a 1 ab 5 dac 9 Output code for W. b 2 bd 6 Set W = c c 3 da 7 d 4 ab 8  d 25
26. 26.  a b d a b d a c  K 1 2 4 5 7 3 a 1 ab 5 dac 9 b 2 bd 6 c 3 da 7 d 4 ab 8 d 26
27. 27. STARTread a character k; K=INPUToutput k; Output Kw = k; W=Kwhile ( read a character k ) YES{ IS EOF STOP ? entry = dictionary entry for k; NO K=NEXT INPUT output entry; add w + entry[0] to ENTRY=DICTIONARY INDEX (K)dictionary; Output ENTRY w = entry; ADD W+ENTRY[0] TO DICTIONARY} W=ENTRY 27
28. 28. LZW 1 2 4 5 7 3 K=1 Out put K (i.e. a) K W=K a a 1 b 2 c 3 d 4 28
29. 29. LZW 1 2 4 5 7 3 K=2 entry = b K Output entry Add W + entry[0] to a b dictionary W = entry (i.e. b) a 1 ab 5 b 2 c 3 d 4 29
30. 30. LZW 1 2 4 5 7 3 K=4 entry = d K Output entry Add W + entry[0] to a b d dictionary W = entry (i.e. d) a 1 ab 5 b 2 bd 6 c 3 d 4 30
31. 31. LZW 1 2 4 5 7 3 K=5 entry = ab K Output entry Add W + entry[0] to a b d a b dictionary W = entry (i.e. ab) a 1 ab 5 b 2 bd 6 c 3 da 7 d 4 31
32. 32. LZW 1 2 4 5 7 3 K=7 entry = da K Output entry Add W + entry[0] to a b d a b d a dictionary W = entry (i.e. da) a 1 ab 5 b 2 bd 6 c 3 da 7 d 4 abd 8 32
33. 33. LZW 1 2 4 5 7 3 K=3 entry = c K Output entry Add W + entry[0] to a b d a b d a c dictionary W = entry (i.e. c) a 1 ab 5 dac 9 b 2 bd 6 c 3 da 7 d 4 abd 8 33
34. 34.   On-the-fly  Adobe PDF   LZMS  34
35. 35.  David Salomon, Data Compression: The Complete Reference, Third Edition, Springer Minh Nguyen, Data Compression presentation en.wikipedia.org/wiki/Data_Compression 35
36. 36. 36