算术编码图象数据压缩标准(如jpeg,jbig)扮演重角色.算术编码,消息01之间实数进行编码.算术编码两基本参数:符号概率它编码间隔.信源符号概率决定压缩编码效率,也决定编码过程信源符号间隔,而这些间隔包含01之间.编码过程间隔决定符号压缩后输出.

算术编码需输入符号,各符号概率还需编码符号序列,根据概率可算出初始编码间隔,先设几变量后面可:High——当前编码限,Low——当前编码限,high——间变量,计算编码符号当前间隔限,low——间变量,计算编码符号当前间隔限,d——当前间隔之间距离.第1编码符号当前间隔其初始编码间隔,第i编码符号当前间隔第i-1编码后[Low,High),第i+1编码符号当前间隔算法如:high=Low+d*第i+1初始编码符号应限,low=Low+d*第i+1编码符号应限,然后High=high,Low=low,d=d*第i编码符号概率.

编码程序如:

#include <iostream.h>

#define M 100

#define N 4

class suanshu

int count,length;

char number[N],n;

long double chance[N],c;

char code[M];

long double High,Low,high,low,d;

public:

suanshu()

{High=0;Low=0;}

void get_number();

void get_code();

void coding();

~suanshu(){}

void suanshu::get_number()

cout<<"please input the number and its chance."<<endl;

for(int i=0;i<N;i++)

cin>>n>>c;

number[i]=n;

chance[i]=c;

if(i==20)

cout<<"the number is full."<<endl;

count=i;

void suanshu::get_code()

cout<<"please input the code''s length:";

cin>>length;

while(length>=M)

cout<<"the length is too larger,please input a smaller one.";

cin>>length;

for(int i=0;i<length;i++)

cin>>code[i];

void suanshu::coding()

int i,j=0;

for(i=0;i<count;i++)

if(code[0]==number[i]) break;

while(j<i)

Low+=chance[j++];

d=chance[j];

High=Low+d;

for(i=1;i<length;i++)

for(j=0;j<count;j++)

if(code[i]==number[j])

if(j==0)

low=Low;

high=Low+chance[j]*d;

High=high;

d*=chance[j];

else

float chance_l=0.0;

for(int k=0;k<=j-1;k++)

chance_l+=chance[k];

low=Low+d*chance_l;

high=Low+d*(chance_l+chance[j]);

Low=low;

High=high;

d*=chance[j];

else continue;

cout<<"the result is:"<<Low<<endl;

int main()

suanshu a;

a.get_number();

a.get_code();

a.coding();

return 0;

本程序VC6.0XP专业版运行通过,这第次c++写比较完整程序,还些尽意方,比如变量函数命名太专业,后注重,慢慢也好.呵呵~