1 using System;
  2 using System.Collections.Generic;
  3 using System.Drawing;
  4 using System.Linq;
  5 using System.Text;
  6 using System.Threading.Tasks;
  7 
  8 namespace DFT
  9 {
 10     class FFT
 11     {
 12         int row;
 13         int col;
 14         double[,] FM;
 15         double[,] FN;
 16         double[,] X;
 17         double[,] Original;
 18         public FFT(String name) 
 19         {
 20             Bitmap bitmap = new Bitmap(name);
 21             this.col = bitmap.Width;
 22             this.row = bitmap.Height;
 23             Original=new double[row,col];
 24             FM=new double[row,row];
 25             FN=new double[col,col];
 26             X=new double[row,col];
 27             for (int i = 0; i < row; i++)
 28             {
 29                 for (int j = 0; j < col; j++)
 30                 {
 31                     Original[i, j] = (bitmap.GetPixel(j,i).R + bitmap.GetPixel(j,i).G + bitmap.GetPixel(j,i).B)/3;
 32                 }
 33             }
 34             initFMN();
 35 
 36         }
 37         public double[,] getFFT()
 38         {
 39             X = martiply(martiply(FM, Original), T(FN));
 40             return X;
 41         }
 42 
 43         public double[,] getIFFT()
 44         {
 45             return martiply(martiply(T(FM), X), FN);
 46         }
 47         private double[,] T(double[,] a)
 48         { 
 49             int awidth = a.GetLength(0);
 50             int aheight = a.GetLength(1);
 51             double[,] reutrnT = new double[aheight, awidth];
 52             for (int i = 0; i < awidth; i++)
 53             {
 54                 for (int j = 0; j < aheight; j++)
 55                 {
 56                     reutrnT[j, i] = a[i, j];
 57                 }
 58             }
 59             return reutrnT;
 60         }
 61         private double[,] martiply(double[,]a,double[,]b)
 62         {
 63             int awidth = a.GetLength(0);
 64             int aheight = a.GetLength(1);
 65             int bheight = b.GetLength(1);
 66             double[,] returnMaxtrix = new double[awidth, bheight];
 67             for (int i = 0; i < awidth; i++)
 68             {
 69                 for (int j = 0; j < bheight; j++)
 70                 {
 71                     for (int k = 0; k < aheight; k++)
 72                     {
 73                         returnMaxtrix[i, j] += a[i, k] * b[k, j];
 74                     }
 75                 }
 76             }
 77             return returnMaxtrix;
 78         }
 79         private void initFMN()
 80         {
 81             double firstm = 1/Math.Sqrt(row);
 82             double firstn = 1 / Math.Sqrt(col);
 83             for (int i = 0; i < row; i++)
 84             {
 85                 for (int j = 0; j < row; j++)
 86                 {
 87                     if (i == 0)
 88                     {
 89                         FM[i, j] = firstm;
 90                     }
 91                     else 
 92                     {
 93                         FM[i, j] = Math.Sqrt(2.0 / row) * Math.Cos(i * j * Math.PI / row);
 94                     }
 95                 }
 96             }
 97             for (int i = 0; i < col; i++)
 98             {
 99                 for (int j = 0; j < col; j++)
100                 {
101                     if (i == 0)
102                     {
103                         FN[i, j] = firstn;
104                     }
105                     else
106                     {
107                         FN[i, j] = Math.Sqrt(2.0 / col) * Math.Cos(i * j * Math.PI / col);
108                     }
109                 }
110             }
111         }
112     }
113 }