Documentation of 'boofcv.alg.transform.fft.GeneralPurposeFFT_F64_2D' Java class
GeneralPurposeFFT_F64_2D
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boofcv.alg.transform.fft

Class GeneralPurposeFFT_F64_2D


  • public class GeneralPurposeFFT_F64_2D
extends java.lang.Object
    Computes 2D Discrete Fourier Transform (DFT) of complex and real, double 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 and Description
      GeneralPurposeFFT_F64_2D(int rows, int columns)
      Creates new instance of DoubleFFT_2D.

    • Method Summary

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

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • GeneralPurposeFFT_F64_2D

        public GeneralPurposeFFT_F64_2D(int rows,
                                int columns)
        Creates new instance of DoubleFFT_2D.
        Parameters:
        rows - number of rows
        columns - number of columns

    • Method Detail

      • complexForward

        public void complexForward(double[] 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 double 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(double[] 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 double 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(double[] 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(double[] 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(double[] 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(double[] 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
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