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using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
namespace WindowsFormsApplication1
{
public struct TKomplex
{
public double real;
public double imag;
}
public partial class MainWin : Form
{
public class TFftAlgorithm
{
int N;
public TKomplex[] we;
public TKomplex[] w;
public TKomplex[] y;
public TKomplex[] c;
public TKomplex ksum(TKomplex a, TKomplex b)
{
TKomplex res;
res.real = a.real + b.real;
res.imag = a.imag + b.imag;
return (res);
}
public TKomplex kdiff(TKomplex a, TKomplex b)
{
TKomplex res;
res.real = a.real - b.real;
res.imag = a.imag - b.imag;
return (res);
}
public TKomplex kprod(TKomplex a, TKomplex b)
{
TKomplex res;
res.real = a.real * b.real - a.imag * b.imag;
res.imag = a.real * b.imag + a.imag * b.real;
return (res);
}
public TFftAlgorithm()
{
w = new TKomplex[1001];
y = new TKomplex[1001];
c = new TKomplex[1001];
}
public void CalcW(int index, int order) // Komplexe Richtungsvektoren w zum Index
{
int i;
for (i = 0; i < order; i++)
{
w[i].real = Math.Cos((double)(2.0 * Math.PI * (double)(i * index) / (double)(order)));
w[i].imag = Math.Sin((double)(2.0 * Math.PI * (double)(i * index) / (double)(order)));
}
}
public void CalcDFT(int N)
{
int k, n;
TKomplex w;
if (N > 0)
{
for (k = 0; k < N; k++)
{
// CalcW(k, order);
c[k].real = 0;
c[k].imag = 0;
for (n = 0; n < N; n++)
{
w.real = Math.Cos((double)(2.0 * Math.PI * (double)(k * n) / (double)(N)));
w.imag = -Math.Sin((double)(2.0 * Math.PI * (double)(k * n) / (double)(N)));
c[k] = ksum(c[k], kprod(w, y[n]));
}
c[k].real = c[k].real / (double)(N) * 2.0;
c[k].imag = -c[k].imag / (double)(N) * 2.0;
}
}
c[0].real = c[0].real / 2;
c[0].imag = c[0].imag / 2;
}
}
TFftAlgorithm fft;
public MainWin()
{
InitializeComponent();
}
private void InitRectangle(TFftAlgorithm fft)
{
int j;
for (j = 0; j < 500; j++)
{
fft.y[j].real = 20.0;
fft.y[j].imag = 0.0;
fft.y[j + 501].real = -20.0;
fft.y[j + 501].imag = 0.0;
}
fft.y[0].real = 0.0;
fft.y[0].imag = 0.0;
fft.y[500].real = 0.0;
fft.y[500].imag = 0.0;
fft.y[1000].real = 0.0;
fft.y[1000].imag = 0.0;
}
private void InitTrytangle(TFftAlgorithm fft)
{
int j;
for (j = 0; j < 500; j++)
{
fft.y[j].real = (double)(j) * 20.0 / 500.0;
fft.y[j].imag = 0.0;
fft.y[j + 501].real = 20.0 - ((double)(j) * 20.0 / 500.0);
fft.y[j+501].imag = 0.0;
}
fft.y[0].real = 0.0;
fft.y[0].imag = 0.0;
fft.y[500].real = 20.0;
fft.y[500].imag = 0.0;
fft.y[1000].real = 0.0;
fft.y[1000].imag = 0.0;
}
private void InitSaw(TFftAlgorithm fft)
{
int j;
for (j = 0; j < 500; j++)
{
fft.y[j].real = (double)(j) * 20.0 / 500.0;
fft.y[j].imag = 0.0;
fft.y[j + 501].real = 0.0; // -(double)(500 - j) * 20.0 / 500.0;
fft.y[j + 501].imag = 0.0;
}
fft.y[0].real = 0.0;
fft.y[0].imag = 0.0;
fft.y[500].real = 20.0;
fft.y[500].imag = 0.0;
fft.y[1000].real = 0.0;
fft.y[1000].imag = 0.0;
}
private void MainWin_Load(object sender, EventArgs e)
{
int j;
fft = new TFftAlgorithm();
Stopwatch timer = new Stopwatch();
DataGridViewCell cell;
InitRectangle(fft);
// InitSaw(fft);
// InitTrytangle(fft);
timer.Start();
fft.CalcDFT(1001);
timer.Stop();
tbTime.Text = timer.ElapsedMilliseconds.ToString();
GResult.RowCount = 30; // DataGridView
for (j = 0; j < GResult.RowCount; j++)
{
cell = GResult[0, j]; // get cell to access
cell.Value = j;
cell = GResult[1, j];
cell.Value = fft.c[j].real;
cell = GResult[2, j];
cell.Value = fft.c[j].imag;
}
}
private void pBild_Paint(object sender, PaintEventArgs e)
{
Point p1, p2;
int order = 1001;
int i, j;
p1 = new Point();
p2 = new Point();
double y1, y2;
Graphics g = pBild.CreateGraphics();
Pen bluePen = new Pen(Color.Blue, 2);
Pen redPen = new Pen(Color.Red, 2);
bluePen.Width = 1;
if (order > 0)
{
for (j = 0; j < order - 1; j++)
{
p1.X = Convert.ToInt32(j / 2);
p1.Y = (pBild.Height / 2) - Convert.ToInt32(Math.Round(fft.y[j].real * 5.0));
p2.X = Convert.ToInt32(j / 2 + 1);
p2.Y = (pBild.Height / 2) - Convert.ToInt32(Math.Round(fft.y[j + 1].real * 5.0));
g.DrawLine(bluePen, p1, p2);
y1 = 0;
y2 = 0;
for (i = 0; i < 50; i++)
{
y1 = y1 + (fft.c[i].real * Math.Cos(2.0 * 3.141592654 * (double)(i * j) / (double)(order)) +
fft.c[i].imag * Math.Sin(2.0 * 3.141592654 * (double)(i * j) / (double)(order)));
y2 = y2 + (fft.c[i].real * Math.Cos(2.0 * 3.141592654 * (double)(i * (j + 1)) / (double)(order)) +
fft.c[i].imag * Math.Sin(2.0 * 3.141592654 * (double)(i * (j + 1)) / (double)(order)));
}
p1.Y = (pBild.Height / 2) - Convert.ToInt32(Math.Round(y1 * 5.0));
p2.Y = (pBild.Height / 2) - Convert.ToInt32(Math.Round(y2 * 5.0));
g.DrawLine(redPen, p1, p2);
}
}
g.Dispose();
}
}
}
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Computers are very straight... They always do exactly what we tell them to do... Only, much too often what we tell them to do is not really what we want them to do
Writing Software is one of the most creative tings one can do. I have been doing this for more than ten years now and still having a lot of fun with it. Besides doing software for HMI's on C# for business, I enjoy very much to implement interesting algorithms and analyse the mathematics they are based on in my leisure time
For more detailed descriptions and math visit me on my own page
www.mosismath.com
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