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~
