dft.cpp

DFT算法实现

#include"stdio.h"
#include "math.h"
#include "graphics.h"
#include "stdlib.h"
#include <conio.h>
#define PI  3.1416
#define N   256

// DFT using common method
float C[N],S[N];//array for storing cos and sin value
void main()
{
  int i,n,k;
  unsigned long int t; // this is the key point--unsiged int
  float x[N]={0},xkr[N]={0},xki[N]={0},xk[N]={0};
  char ch[50],cha;
  void draw(float data[],int num,int ratio,char ch[]);
  void DFT(float x[],float xkr[],float xki[],float xk[]);

  for(i=0;i<N;i++)
   {
	 C[i]=cos(2*PI*i/N);
	 S[i]=sin(2*PI*i/N);
   }


   for(i=0;i<200;i++)
   {

	x[i]=sin(PI*i/N);

  }



  DFT(x,xkr,xki,xk);

	   sprintf(ch,"x[n]");
	   draw(x,N,50,ch);
	   sprintf(ch,"|xk[N]|");
	   draw(xk,N,2,ch);
}




void DFT(float x[],float xkr[],float xki[],float xk[])
{
  int n,k;
  unsigned long int t;
 for(k=0;k<N;k++)
   {
	  for(n=0;n<N;n++)
	   {    
		 t=n*k;
		 xkr[k]=xkr[k]+x[n]*C[t%N];
		 xki[k]=xki[k]+x[n]*S[t%N];
	   }
	   xk[k]=sqrt(xkr[k]*xkr[k]+xki[k]*xki[k]);
           xkr[k]=0; xki[k]=0;// clear intermedia value 
   }

}
void draw(float data[],int num,int ratio,char ch[])
{
  int i,xb,xe,yb,ye,oy;
  int gdriver = DETECT,gmode;
  char buff[50];

  initgraph(&gdriver,&gmode,"d:\\tc30\\bgi");
  cleardevice();
  setbkcolor(0);  //set the  background black
  setcolor(30);  //set the axis yellow
  xb=20;xe=630;yb=50; ye=450; oy=(yb+ye)/2;
  yb=20;


  line(xb,oy,xe,oy);  //draw x axis
  outtextxy(xe,oy-2,">");
  outtextxy(xe-5,oy+3,"n");

  line(xb,yb,xb,ye);  //dray Y axis
  outtextxy(xb-3,yb-2,"^");
  outtextxy(xb+3,yb-2,ch);


  for(i=0;i<4;i++)
  {
   line(xb,oy-i*50,xb+3,oy-i*50);
   sprintf(buff,"%d",i);
   outtextxy(xb-10,oy-i*50,buff);
   }


	for(i=0;i<610;i++)
  {
	if(i==40*int(i/40))
	 {
		line(xb+i,oy+5,xb+i,oy);
		sprintf(buff,"%d",i/2);
		if(i!=0)
		outtextxy(xb+i-5,oy+10,buff);
	 }
  }


  for(i=1;i<num;i++)
  {
	setcolor(12);
   //	line(xb+(i*2-1), oy-data[i-1]*ratio,xb+i*2,oy-data[i]*ratio);
	 line(xb+(i*2-2), oy,xb+i*2-2,oy-data[i]*ratio);  //line graph
  }

  getchar();
  closegraph();

}