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84 lines
3.9 KiB
Java
84 lines
3.9 KiB
Java
/*
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This is the java implementation of performing Discrete Fourier Transform using Fast Fourier Transform algorithm. This class finds the DFT of N (power of 2) complex elements, generated randomly, using FFT. The input to the class is a two dimensional array of sequence.
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*/
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//This is a sample program to perform 2D FFT inplace
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import java.util.Scanner;
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public class TwoD_FFT
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{
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static void twoDfft(double[][] inputData, double[][] realOut,
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double[][] imagOut, double[][] amplitudeOut)
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{
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int height = inputData.length;
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int width = inputData[0].length;
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// Two outer loops iterate on output data.
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for (int yWave = 0; yWave < height; yWave++)
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{
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for (int xWave = 0; xWave < width; xWave++)
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{
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// Two inner loops iterate on input data.
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for (int ySpace = 0; ySpace < height; ySpace++)
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{
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for (int xSpace = 0; xSpace < width; xSpace++)
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{
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// Compute real, imag, and ampltude.
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realOut[yWave][xWave] += (inputData[ySpace][xSpace] * Math
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.cos(2
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* Math.PI
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* ((1.0 * xWave * xSpace / width) + (1.0
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* yWave * ySpace / height))))
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/ Math.sqrt(width * height);
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imagOut[yWave][xWave] -= (inputData[ySpace][xSpace] * Math
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.sin(2
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* Math.PI
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* ((1.0 * xWave * xSpace / width) + (1.0
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* yWave * ySpace / height))))
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/ Math.sqrt(width * height);
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amplitudeOut[yWave][xWave] = Math
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.sqrt(realOut[yWave][xWave]
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* realOut[yWave][xWave]
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+ imagOut[yWave][xWave]
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* imagOut[yWave][xWave]);
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}
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System.out.println(realOut[yWave][xWave] + " + "
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+ imagOut[yWave][xWave] + " i");
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}
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}
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}
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}
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public static void main(String args[])
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{
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System.out.println("Enter the size: ");
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Scanner sc = new Scanner(System.in);
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int n = sc.nextInt();
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double[][] input = new double[n][n];
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double[][] real = new double[n][n];
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double[][] img = new double[n][n];
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double[][] amplitutude = new double[n][n];
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System.out.println("Enter the 2D elements ");
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for (int i = 0; i < n; i++)
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for (int j = 0; j < n; j++)
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input[i][j] = sc.nextDouble();
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twoDfft(input, real, img, amplitutude);
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sc.close();
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}
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}
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/*
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Enter the size:
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2
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Enter the 2D elements
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2 3
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4 2
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2.5 + 0.0 i
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5.5 + 0.0 i
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-0.5 + -1.8369701987210297E-16 i
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0.5 + -3.0616169978683826E-16 i
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2.5 + 0.0 i
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-0.5 + -3.6739403974420594E-16 i
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-0.5 + -1.8369701987210297E-16 i
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-1.5 + -1.8369701987210297E-16 i
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