Package boofcv.alg.transform.fft

Class GeneralPurposeFFT_F32_2D

java.lang.Object
boofcv.alg.transform.fft.GeneralPurposeFFT_F32_2D
public class GeneralPurposeFFT_F32_2D extends Object

Computes 2D Discrete Fourier Transform (DFT) of complex and real, float precision data. The size of the data can be an arbitrary number. The code originally comes from General Purpose FFT Package written by Takuya Ooura (http://www.kurims.kyoto-u.ac.jp/~ooura/fft.html). See below for the full history.

This code has a bit of a history. Originally from General Purpose FFT. Which was then ported into JFFTPack written by Baoshe Zhang (http://jfftpack.sourceforge.net/), and then into JTransforms by Piotr Wendykier. The major modification from JTransforms is that the SMP code has been stripped out. It might be added back in once an SMP strategy has been finalized in BoofCV.

Code License: The original license of General Purpose FFT Package is shown below. This file will fall under the same license: 

 Copyright Takuya OOURA, 1996-2001

 You may use, copy, modify and distribute this code for any purpose (include commercial use) and without fee.
 Please refer to this package when you modify this code.

  • Constructor Summary

    Constructors
    Constructor
    Description
    GeneralPurposeFFT_F32_2D(int rows, int columns)
    Creates new instance of DoubleFFT_2D.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    complexForward(float[] a)
    Computes 2D forward DFT of complex data leaving the result in a.
    void
    complexInverse(float[] a, boolean scale)
    Computes 2D inverse DFT of complex data leaving the result in a.
    void
    realForward(float[] a)
    Computes 2D forward DFT of real data leaving the result in a .
    void
    realForwardFull(float[] a)
    Computes 2D forward DFT of real data leaving the result in a .
    void
    realInverse(float[] a, boolean scale)
    Computes 2D inverse DFT of real data leaving the result in a .
    void
    realInverseFull(float[] a, boolean scale)
    Computes 2D inverse DFT of real data leaving the result in a .

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • GeneralPurposeFFT_F32_2D

      public GeneralPurposeFFT_F32_2D(int rows, int columns)
      Creates new instance of DoubleFFT_2D.
      Parameters:
      rows - number of rows
      columns - number of columns

  • Method Details

    • complexForward

      public void complexForward(float[] a)
      Computes 2D forward DFT of complex data leaving the result in a. The data is stored in 1D array in row-major order. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the input array must be of size rows*2*columns. The physical layout of the input data has to be as follows:
       a[k1*2*columns+2*k2] = Re[k1][k2],
 a[k1*2*columns+2*k2+1] = Im[k1][k2], 0<=k1<rows, 0<=k2<columns,
      Parameters:
      a - data to transform

    • complexInverse

      public void complexInverse(float[] a, boolean scale)
      Computes 2D inverse DFT of complex data leaving the result in a. The data is stored in 1D array in row-major order. Complex number is stored as two float values in sequence: the real and imaginary part, i.e. the input array must be of size rows*2*columns. The physical layout of the input data has to be as follows:
       a[k1*2*columns+2*k2] = Re[k1][k2],
 a[k1*2*columns+2*k2+1] = Im[k1][k2], 0<=k1<rows, 0<=k2<columns,
      Parameters:
      a - data to transform
      scale - if true then scaling is performed

    • realForward

      public void realForward(float[] a)
      Computes 2D forward DFT of real data leaving the result in a . This method only works when the sizes of both dimensions are power-of-two numbers. The physical layout of the output data is as follows: 
       a[k1*columns+2*k2] = Re[k1][k2] = Re[rows-k1][columns-k2],
 a[k1*columns+2*k2+1] = Im[k1][k2] = -Im[rows-k1][columns-k2],
       0<k1<rows, 0<k2<columns/2,
 a[2*k2] = Re[0][k2] = Re[0][columns-k2],
 a[2*k2+1] = Im[0][k2] = -Im[0][columns-k2],
       0<k2<columns/2,
 a[k1*columns] = Re[k1][0] = Re[rows-k1][0],
 a[k1*columns+1] = Im[k1][0] = -Im[rows-k1][0],
 a[(rows-k1)*columns+1] = Re[k1][columns/2] = Re[rows-k1][columns/2],
 a[(rows-k1)*columns] = -Im[k1][columns/2] = Im[rows-k1][columns/2],
       0<k1<rows/2,
 a[0] = Re[0][0],
 a[1] = Re[0][columns/2],
 a[(rows/2)*columns] = Re[rows/2][0],
 a[(rows/2)*columns+1] = Re[rows/2][columns/2]
      This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real forward transform, use realForwardFull. To get back the original data, use realInverse on the output of this method.
      Parameters:
      a - data to transform

    • realForwardFull

      public void realForwardFull(float[] a)
      Computes 2D forward DFT of real data leaving the result in a . This method computes full real forward transform, i.e. you will get the same result as from complexForward called with all imaginary part equal 0. Because the result is stored in a, the input array must be of size rows*2*columns, with only the first rows*columns elements filled with real data. To get back the original data, use complexInverse on the output of this method.
      Parameters:
      a - data to transform

    • realInverse

      public void realInverse(float[] a, boolean scale)
      Computes 2D inverse DFT of real data leaving the result in a . This method only works when the sizes of both dimensions are power-of-two numbers. The physical layout of the input data has to be as follows: 
       a[k1*columns+2*k2] = Re[k1][k2] = Re[rows-k1][columns-k2],
 a[k1*columns+2*k2+1] = Im[k1][k2] = -Im[rows-k1][columns-k2],
       0<k1<rows, 0<k2<columns/2,
 a[2*k2] = Re[0][k2] = Re[0][columns-k2],
 a[2*k2+1] = Im[0][k2] = -Im[0][columns-k2],
       0<k2<columns/2,
 a[k1*columns] = Re[k1][0] = Re[rows-k1][0],
 a[k1*columns+1] = Im[k1][0] = -Im[rows-k1][0],
 a[(rows-k1)*columns+1] = Re[k1][columns/2] = Re[rows-k1][columns/2],
 a[(rows-k1)*columns] = -Im[k1][columns/2] = Im[rows-k1][columns/2],
       0<k1<rows/2,
 a[0] = Re[0][0],
 a[1] = Re[0][columns/2],
 a[(rows/2)*columns] = Re[rows/2][0],
 a[(rows/2)*columns+1] = Re[rows/2][columns/2]
      This method computes only half of the elements of the real transform. The other half satisfies the symmetry condition. If you want the full real inverse transform, use realInverseFull.
      Parameters:
      a - data to transform
      scale - if true then scaling is performed

    • realInverseFull

      public void realInverseFull(float[] a, boolean scale)
      Computes 2D inverse DFT of real data leaving the result in a . This method computes full real inverse transform, i.e. you will get the same result as from complexInverse called with all imaginary part equal 0. Because the result is stored in a, the input array must be of size rows*2*columns, with only the first rows*columns elements filled with real data.
      Parameters:
      a - data to transform
      scale - if true then scaling is performed