GIF LZW数据分析

Author:zfive5(zhaozidong)

Email :zfive5@yahoo.com.cn

点阵(16X16)

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

压缩数据

00 FF 09 1C  48 B0 A0 C1  83 08 12 2A  5C C8 B0 A1

C3 87 10 23  4A 9C 48 B1  A2 C5 81 01  01

00   0000 0000     

FF   1111 1111      1 0000 0000           

09   0000 1001      0 1111 1111

1C   0001 1100      0 1000 0010

48   0100 1000      1 0000 0011

B0   1011 0000      1 0000 0100

A0   1010 0000      1 0000 0101

C1   1100 0001      1 0000 0110

83   1000 0011      1 0000 0111

08   0000 1000      1 0000 1000

13   0001 0011     

2A   0010 1010      1 0000 1001

5C   0101 1100      1 0000 1010

C8   1100 1000      1 0000 1011

B0   1011 0000      1 0000 1100 

A1   1010 0001      1 0000 1101

C3   1100 0011      1 0000 1110

87   1000 0111      1 0000 1111

10   0001 0000     

23   0010 0011      1 0001 0000

4a   0100 1010      1 0001 0001

9c   1001 1100      1 0001 0010

48   0100 1000      1 0001 0011

b1   1011 0001      1 0001 0100

a2   1010 0010      1 0001 0101

c5   1100 0101      1 0001 0110

81   1000 0001      1 0000 0011

01   0000 0001     

01   0000 0001      1 0000 0001

 (1+22)/2*22+3=256

参考

压缩算法

[1] initialize string table;

[2] [.c.] <- empty;    

[3] k <- next character in charstream;    

[4] is [.c.]k in string table?     

(yes:

     [.c.] <- [.c.]k;           

     go to [3];     

)     

(no:

     add [.c.]k to the string table;

     output the code for [.c.] to the codestream;

     [.c.] <- k;

     go to [3];     

 )

    

解压算法

[1] initialize string table;

[2] get first code: <code>;

[3] output the string for <code> to the charstream;

[4] <old> = <code>;

[5] <code> <- next code in codestream;

[6] does <code> exist in the string table?

(yes:

     output the string for <code> to the charstream;

     [...] <- translation for <old>;

     k <- first character of translation for <code>;

     add [...]k to the string table;

     <old> <- <code>; 

)     

(no:

     [...] <- translation for <old>;

     k <- first character of [...];

     output [...]k to charstream and add it to string table;

     <old> <- <code>

)    

[7] go to [5];