jacenc.m

灰度图像的jpeg压缩处理

function b=jacenc(x)
% Usage: b=jacenc(x)
% JPEG AC coefficient encoding routine
% x: AC coefficient sequence 
% b: corresponding bit stream
% copyright (c) 1997 by Yu Hen Hu
%
% created: 11/25/97
%

b=[];
%    run - category - length - bsae code length -  base code
table=[...
 0  1   3  2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 0  2   4  2 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 0  3   6  3 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
 0  4   8  4 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0
 0  5  10  5 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 
 0  6  12  6 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 
 0  7  14  7 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 
 0  8  18 10 1 1 1 1 1 1 0 1 1 0 0 0 0 0 0 0
 0  9  25 16 1 1 1 1 1 1 1 1 1 0 0 0 0 0 1 0
 0 10  26 16 1 1 1 1 1 1 1 1 1 0 0 0 0 0 1 1
 1  1   5  4 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 
 1  2   8  6 1 1 1 0 0 1 0 0 0 0 0 0 0 0 0 0 
 1  3  10  7 1 1 1 1 0 0 1 0 0 0 0 0 0 0 0 0
 1  4  13  9 1 1 1 1 1 0 1 1 0 0 0 0 0 0 0 0
 1  5  16 11 1 1 1 1 1 1 1 0 1 1 0 0 0 0 0 0
 1  6  22 16 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 0
 1  7  23 16 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0 1
 1  8  24 16 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 0
 1  9  25 16 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1
 1 10  26 16 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0 0
 2  1   6  5 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 
 2  2  10  8 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0
 2  3  13 10 1 1 1 1 1 1 0 1 1 1 0 0 0 0 0 0 
 2  4  20 16 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0 1
 2  5  21 16 1 1 1 1 1 1 1 1 1 0 0 0 1 0 1 0
 2  6  22 16 1 1 1 1 1 1 1 1 1 0 0 0 1 0 1 1
 2  7  23 16 1 1 1 1 1 1 1 1 1 0 0 0 1 1 0 0
 2  8  24 16 1 1 1 1 1 1 1 1 1 0 0 0 1 1 0 1
 2  9  25 16 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 0
 2 10  26 16 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 1
 3  1   7  6 1 1 1 0 1 0 0 0 0 0 0 0 0 0 0 0
 3  2  11  9 1 1 1 1 1 0 1 1 1 0 0 0 0 0 0 0
 3  3  14 11 1 1 1 1 1 1 1 0 1 1 1 0 0 0 0 0 
 3  4  20 16 1 1 1 1 1 1 1 1 1 0 0 1 0 0 0 0
 3  5  21 16 1 1 1 1 1 1 1 1 1 0 0 1 0 0 0 1
 3  6  22 16 1 1 1 1 1 1 1 1 1 0 0 1 0 0 1 0
 3  7  23 16 1 1 1 1 1 1 1 1 1 0 0 1 0 0 1 1
 3  8  24 16 1 1 1 1 1 1 1 1 1 0 0 1 0 1 0 0
 3  9  25 16 1 1 1 1 1 1 1 1 1 0 0 1 0 1 0 1
 3 10  26 16 1 1 1 1 1 1 1 1 1 0 0 1 0 1 1 0
 4  1   7  6 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0 0
 4  2  12 10 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 
 4  3  19 16 1 1 1 1 1 1 1 1 1 0 0 1 0 1 1 1
 4  4  20 16 1 1 1 1 1 1 1 1 1 0 0 1 1 0 0 0
 4  5  21 16 1 1 1 1 1 1 1 1 1 0 0 1 1 0 0 1
 4  6  22 16 1 1 1 1 1 1 1 1 1 0 0 1 1 0 1 0
 4  7  23 16 1 1 1 1 1 1 1 1 1 0 0 1 1 0 1 1
 4  8  24 16 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0 0
 4  9  25 16 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0 1
 4 10  26 16 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 0
 5  1   8  7 1 1 1 1 0 1 0 0 0 0 0 0 0 0 0 0
 5  2  12 10 1 1 1 1 1 1 1 0 0 1 0 0 0 0 0 0 
 5  3  19 16 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1 1
 5  4  20 16 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0
 5  5  21 16 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0 1
 5  6  22 16 1 1 1 1 1 1 1 1 1 0 1 0 0 0 1 0
 5  7  23 16 1 1 1 1 1 1 1 1 1 0 1 0 0 0 1 1
 5  8  24 16 1 1 1 1 1 1 1 1 1 0 1 0 0 1 0 0
 5  9  25 16 1 1 1 1 1 1 1 1 1 0 1 0 0 1 0 1
 5 10  26 16 1 1 1 1 1 1 1 1 1 0 1 0 0 1 1 0
 6  1   8  7 1 1 1 1 0 1 1 0 0 0 0 0 0 0 0 0
 6  2  13 11 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 
 6  3  19 16 1 1 1 1 1 1 1 1 1 0 1 0 0 1 1 1
 6  4  20 16 1 1 1 1 1 1 1 1 1 0 1 0 1 0 0 0
 6  5  21 16 1 1 1 1 1 1 1 1 1 0 1 0 1 0 0 1
 6  6  22 16 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1 0
 6  7  23 16 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1 1
 6  8  24 16 1 1 1 1 1 1 1 1 1 0 1 0 1 1 0 0
 6  9  25 16 1 1 1 1 1 1 1 1 1 0 1 0 1 1 0 1
 6 10  26 16 1 1 1 1 1 1 1 1 1 0 1 0 1 1 1 0
 7  1   9  8 1 1 1 1 1 0 0 1 0 0 0 0 0 0 0 0
 7  2  14 12 1 1 1 1 1 1 1 1 0 1 1 1 0 0 0 0
 7  3  19 16 1 1 1 1 1 1 1 1 1 0 1 0 1 1 1 1
 7  4  20 16 1 1 1 1 1 1 1 1 1 0 1 1 0 0 0 0
 7  5  21 16 1 1 1 1 1 1 1 1 1 0 1 1 0 0 0 1
 7  6  22 16 1 1 1 1 1 1 1 1 1 0 1 1 0 0 1 0
 7  7  23 16 1 1 1 1 1 1 1 1 1 0 1 1 0 0 1 1
 7  8  24 16 1 1 1 1 1 1 1 1 1 0 1 1 0 1 0 0
 7  9  25 16 1 1 1 1 1 1 1 1 1 0 1 1 0 1 0 1
 7 10  26 16 1 1 1 1 1 1 1 1 1 0 1 1 0 1 1 0
 8  1   9  8 1 1 1 1 1 0 1 0 0 0 0 0 0 0 0 0
 8  2  17 15 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0
 8  3  19 16 1 1 1 1 1 1 1 1 1 0 1 1 0 1 1 1
 8  4  20 16 1 1 1 1 1 1 1 1 1 0 1 1 1 0 0 0
 8  5  21 16 1 1 1 1 1 1 1 1 1 0 1 1 1 0 0 1
 8  6  22 16 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1 0
 8  7  23 16 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1 1
 8  8  24 16 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0 0
 8  9  25 16 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0 1
 8 10  26 16 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 0
 9  1  10  9 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 
 9  2  18 16 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1
 9  3  19 16 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0
 9  4  20 16 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 1
 9  5  21 16 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 0
 9  6  22 16 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1
 9  7  23 16 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0 0
 9  8  24 16 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0 1
 9  9  25 16 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 0
 9 10  26 16 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1
10  1  10  9 1 1 1 1 1 1 0 0 1 0 0 0 0 0 0 0 
10  2  18 16 1 1 1 1 1 1 1 1 1 1 0 0 1 0 0 0
10  3  19 16 1 1 1 1 1 1 1 1 1 1 0 0 1 0 0 1
10  4  20 16 1 1 1 1 1 1 1 1 1 1 0 0 1 0 1 0
10  5  21 16 1 1 1 1 1 1 1 1 1 1 0 0 1 0 1 1
10  6  22 16 1 1 1 1 1 1 1 1 1 1 0 0 1 1 0 0
10  7  23 16 1 1 1 1 1 1 1 1 1 1 0 0 1 1 0 1
10  8  24 16 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 0
10  9  25 16 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1 1
10 10  26 16 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 0
11  1  10  9 1 1 1 1 1 1 0 1 0 0 0 0 0 0 0 0 
11  2  18 16 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0 1
11  3  19 16 1 1 1 1 1 1 1 1 1 1 0 1 0 0 1 0
11  4  20 16 1 1 1 1 1 1 1 1 1 1 0 1 0 0 1 1
11  5  21 16 1 1 1 1 1 1 1 1 1 1 0 1 0 1 0 0
11  6  22 16 1 1 1 1 1 1 1 1 1 1 0 1 0 1 0 1
11  7  23 16 1 1 1 1 1 1 1 1 1 1 0 1 0 1 1 0
11  8  24 16 1 1 1 1 1 1 1 1 1 1 0 1 0 1 1 1
11  9  25 16 1 1 1 1 1 1 1 1 1 1 0 1 1 0 0 0
11 10  26 16 1 1 1 1 1 1 1 1 1 1 0 1 1 0 0 1
12  1  11 10 1 1 1 1 1 1 1 0 1 0 0 0 0 0 0 0 
12  2  18 16 1 1 1 1 1 1 1 1 1 1 0 1 1 0 1 0
12  3  19 16 1 1 1 1 1 1 1 1 1 1 0 1 1 0 1 1
12  4  20 16 1 1 1 1 1 1 1 1 1 1 0 1 1 1 0 0
12  5  21 16 1 1 1 1 1 1 1 1 1 1 0 1 1 1 0 1
12  6  22 16 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 0
12  7  23 16 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1
12  8  24 16 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0
12  9  25 16 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1
12 10  26 16 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 0
13  1  12 11 1 1 1 1 1 1 1 1 0 1 0 0 0 0 0 0 
13  2  18 16 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1
13  3  19 16 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0 0
13  4  20 16 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0 1
13  5  21 16 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1 0
13  6  22 16 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1 1
13  7  23 16 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 0
13  8  24 16 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0 1
13  9  25 16 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1 0
13 10  26 16 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1 1
14  1  13 12 1 1 1 1 1 1 1 1 0 1 1 0 0 0 0 0
14  2  18 16 1 1 1 1 1 1 1 1 1 1 1 0 1 1 0 0
14  3  19 16 1 1 1 1 1 1 1 1 1 1 1 0 1 1 0 1
14  4  20 16 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 0
14  5  21 16 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1
14  6  22 16 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0
14  7  23 16 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1
14  8  24 16 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 0
14  9  25 16 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1 1
14 10  26 16 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 0
15  1  17 16 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1
15  2  18 16 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 0
15  3  19 16 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1
15  4  20 16 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0
15  5  21 16 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 1
15  6  22 16 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0
15  7  23 16 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1
15  8  24 16 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0
15  9  25 16 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1
15 10  26 16 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0
 0  0   4  4 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0
15  0  11 11 1 1 1 1 1 1 1 1 0 0 1 0 0 0 0 0];


ix = find(x~=0); % index of next non-zero entry 找到不为零的数值的坐标例如x=[0,0,0,1,1,0,0],ix = find(x~=0),值为ix=[4,5]
                                               %即第4位以及第5位部位零。
Nx = length(ix);  % # of non-zero entries      非零数的个数

% if first ac coefficient has no leading zeros
% then encode x(1)!
% note much details have been left out here
% we did not concern what if Nx=1 and x(1)=EoB
% 在程序tobdel中有详细的处理，但是对它们对EoB都没有处理，开头

if ix(1)==1,  
   run=0;   % no leading zero    游程长度
   tmp=int2bin(x(1));  % tmp is 1 by (c+1) 把非零数值由10进制转化为2进制；这里的这个函数是自己写的int2bin(12)=01100;int2bin(-12)= 11100
   cat=length(tmp)-1;  % first bit is sign bit （数值的绝对值所占用的位数，即是相当于组号）
   row=run*10+cat;     %通过游程长度确定该数据在表中的行的位置。（因为每一个游程对应的是10行）
   prefix=table(row,5:table(row,4)+4); %prefix,是对AC系数的符号1进行查表编码，5:table(row,4)+4对应的码字的坐标，从第5列开始，结束的坐标位置是
                                       %table(row,4)为每一行的第4列，对应的值是符号1对应的码字的
                                       %码长，加上4是码字的最后一位对应的坐标
   if tmp(1)==1,  %if current x is negative  利用函数int2bin转化之后第一位为1则是负数，else是整数
      tmp=ones(1,cat+1)-tmp; % 1's complement ，这里利用减法实现了编码，其实对其取反效果是一样的（注意补码＆反码的不同，都可以通过减法来实现）
   end                       %正数不需要处理
   b=[prefix tmp(2:cat+1)];  %AC编码完毕，其中一位的编码完毕
end

for n=2:Nx, % loop through each non-zero entry Nx是非零数的个数，对每一个位数进行编码
   prefix=[];
   % 1. ck # of leading zeros
   run=ix(n)-ix(n-1)-1;                     %两个非零数字之间的游程数目
 %因为编码中符号1中用来表示游程的长短的位数是4位，所以只能到（15，0）就是连续15个零，当游程的长度超过15是可以考虑
 %在其中间添加码字（15，0）
                                   
    % 2. ck if run > 16;                    
   %  run of 0s longer than 15, will be broken down into repeated
   %  run-of-15-0 symbol
   while run > 15, 
      b=[b 1 1 1 1 1 1 1 1 0 0 1];
      run=run-15;
   end
   % check if end of block
   if x(ix(n))==999, 
       b = [b 1 0 1 0];  % append EoB symbol
   else
      tmp=int2bin(x(ix(n)));  % tmp is 1 by (c+1)
      cat=length(tmp)-1;  % first bit is sign bit
      row=run*10+cat;     % row number of the prefix Hoffman code
      prefix=table(row,5:table(row,4)+4);
      if tmp(1)==1,       % if current x is negative 
         tmp=ones(1,cat+1)-tmp; % 1's complement
      end
      b=[b prefix tmp(2:cat+1)];  %处理同上面的第一位的处理
   end
end