开发学院软件开发VC DCT快速变换 阅读

DCT快速变换

 2010-07-25 20:45:40 来源:WEB开发网   
核心提示:DCT变换过程可分为两部分:前向追底和后向回根前向追底:void dct_forward(double *f,int deg){// f中存储DCT数据int i_deg, i_halfwing, total, wing, wings, winglen, halfwing;double temp1,temp2;tota

DCT变换过程可分为两部分:前向追底和后向回根

前向追底:

void dct_forward(double *f,int deg)
{
   // f中存储DCT数据
   int i_deg, i_halfwing, total, wing, wings, winglen, halfwing;
   double temp1,temp2;
   total = 1 << deg;
   for(i_deg = 0; i_deg < deg; i_deg++)
   {
       wings = 1 << i_deg;
       winglen = total >> i_deg;
       halfwing = winglen >> 1;
       for(wing = 0; wing < wings; wing++)
       {
          for(i_halfwing = 0; i_halfwing < halfwing; i_halfwing++)
          {
              temp1 = f[wing*winglen+i_halfwing];
              temp2 = f[(wing+1)*winglen-1-i_halfwing];
              if(wing%2)
                 swap(temp1,temp2); // 交换temp1与temp2的值
              f[wing*winglen+i_halfwing] = temp1+temp2;
              f[(wing+1)*winglen-1-i_halfwing] =
                (temp1-temp2)*C[winglen-1-i_halfwing];
          }
       }
   }
}

后向回根:

void dct_backward(double *f,int deg)
{
   // f中存储DCT数据
   int total,i_deg,wing,wings,halfwing,winglen,i_halfwing,temp1,temp2;
   total = 1 << deg;
   for(i_deg = deg-1; i_deg >= 0; i_deg--)
   {
       wings = 1 << i_deg;
       winglen = 1 << (deg-i_deg);
       halfwing = winglen >> 1;
       for(wing = 0; wing < wings; wing++)
       {
          for(i_halfwing = 0; i_halfwing < halfwing; i_halfwing++)
          {
              //f[i_halfwing+wing*winglen] = f[i_halfwing+wing*winglen];
              if(i_halfwing == 0)
              {
                  f[halfwing+wing*winglen+i_halfwing] =
                    0.5*f[halfwing+wing*winglen+i_halfwing];
              }
              else
              {
                 temp1=bitrev(i_halfwing,deg-i_deg-1);  // bitrev为位反序
                 temp2=bitrev(i_halfwing-1,deg-i_deg-1); // 第一参数为要变换的数
                 // 第二参数为二进制长度
                 f[halfwing+wing*winglen+temp1] =
                    f[halfwing+wing*winglen+temp1]-f[halfwing+wing*winglen+temp2];
              }
          }
       }
   }
}

上一页  1 2 3 4 5 6 7  下一页

Tags:DCT 快速 变换

编辑录入:爽爽 [复制链接] [打 印]
[]
  • 好
  • 好的评价 如果觉得好,就请您
      0%(0)
  • 差
  • 差的评价 如果觉得差,就请您
      0%(0)
赞助商链接