com.pearsoneduc.ip.op
Class ImageFFT

java.lang.Object
  |
  +--com.pearsoneduc.ip.op.ImageFFT

public class ImageFFT

extends java.lang.Object

Computes the FFT of an image, and the inverse FFT of its frequency domain representation. The transformed data can be inspected or filtered before performing the inverse transform.

Version:

1.3 [1999/08/09]

Author:

Nick Efford

See Also:

FFTException, BufferedImage

Field Summary

static int	BARTLETT_WINDOW
static int	HAMMING_WINDOW
static int	HANNING_WINDOW
static int	NO_WINDOW

Constructor Summary

ImageFFT(java.awt.image.BufferedImage image)
Creates an ImageFFT for the specified image.

ImageFFT(java.awt.image.BufferedImage image, int win)
Creates an ImageFFT for the specified image, applying the specified windowing function to the data.

Method Summary

static double	bartlettWindow(double r, double rmax) Computes one half of a radial Bartlett windowing function.
void	butterworthBandPassFilter(double radius, double delta) Performs order-1 Butterworth band pass filtering of the spectrum.
void	butterworthBandPassFilter(int n, double radius, double delta) Performs Butterworth band pass filtering of the spectrum.
static double	butterworthBandPassFunction(int n, double radius, double delta, double r) Computes the transfer function for a Butterworth band pass filter.
void	butterworthBandStopFilter(double radius, double delta) Performs order-1 Butterworth band stop filtering of the spectrum.
void	butterworthBandStopFilter(int n, double radius, double delta) Performs Butterworth band stop filtering of the spectrum.
static double	butterworthBandStopFunction(int n, double radius, double delta, double r) Computes the transfer function of a Butterworth band stop filter.
void	butterworthHighPassFilter(double radius) Performs order-1 Butterworth high pass filtering of the spectrum.
void	butterworthHighPassFilter(int n, double radius) Performs Butterworth high pass filtering of the spectrum.
static double	butterworthHighPassFunction(int n, double radius, double r) Computes the transfer function for a Butterworth high pass filter.
void	butterworthLowPassFilter(double radius) Performs order-1 Butterworth low pass filtering of the spectrum.
void	butterworthLowPassFilter(int n, double radius) Performs Butterworth low pass filtering of the spectrum.
static double	butterworthLowPassFunction(int n, double radius, double r) Computes the transfer function for a Butterworth low pass filter.
int	getHeight()
float	getMagnitude(int u, int v) Computes magnitude for any point in the spectrum.
float	getPhase(int u, int v) Computes phase for any point in the spectrum.
java.awt.image.BufferedImage	getSpectrum() Returns the amplitude spectrum of an image, as another image.
java.awt.image.BufferedImage	getUnshiftedSpectrum() Returns the amplitude spectrum of an image, as another image.
int	getWidth()
int	getWindow()
static double	hammingWindow(double r, double rmax) Computes one half of a radial Hamming windowing function.
static double	hanningWindow(double r, double rmax) Computes one half of a radial Hanning windowing function.
void	idealBandPassFilter(double radius, double delta) Performs ideal band pass filtering on the spectrum.
void	idealBandStopFilter(double radius, double delta) Performs ideal band stop filtering on the spectrum.
void	idealHighPassFilter(double radius) Performs ideal high pass filtering on the spectrum.
void	idealLowPassFilter(double radius) Performs ideal low pass filtering on the spectrum.
boolean	isSpectral()
void	setMagnitude(int u, int v, float mag) Modifies magnitude at any point in the spectrum.
void	setPhase(int u, int v, float phase) Modifies phase at any point in the spectrum.
java.awt.image.BufferedImage	toImage(java.awt.image.BufferedImage image) Converts stored data into an image.
java.awt.image.BufferedImage	toImage(java.awt.image.BufferedImage image, int bias) Converts stored data into an image.
java.lang.String	toString()
void	transform() Transforms data via a forward or inverse FFT, as appropriate.

Methods inherited from class java.lang.Object

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

Field Detail

NO_WINDOW

public static final int NO_WINDOW

BARTLETT_WINDOW

public static final int BARTLETT_WINDOW

HAMMING_WINDOW

public static final int HAMMING_WINDOW

HANNING_WINDOW

public static final int HANNING_WINDOW

Constructor Detail

ImageFFT

public ImageFFT(java.awt.image.BufferedImage image)
         throws FFTException

Creates an ImageFFT for the specified image. There will be no windowing of image data.

Parameters:

image - input image

Throws:

FFTException - if the image is not 8-bit greyscale.

ImageFFT

public ImageFFT(java.awt.image.BufferedImage image,
                int win)
         throws FFTException

Creates an ImageFFT for the specified image, applying the specified windowing function to the data.

Parameters:

image - input image

win - windowing function

Throws:

FFTException - if the image is not 8-bit greyscale.

Method Detail

bartlettWindow

public static final double bartlettWindow(double r,
                                          double rmax)

Computes one half of a radial Bartlett windowing function.

Parameters:

r - distance from centre of data

rmax - maximum distance

Returns:

function value.

hammingWindow

public static final double hammingWindow(double r,
                                         double rmax)

Computes one half of a radial Hamming windowing function.

Parameters:

r - distance from centre of data

rmax - maximum distance

Returns:

function value.

hanningWindow

public static final double hanningWindow(double r,
                                         double rmax)

Computes one half of a radial Hanning windowing function.

Parameters:

r - distance from centre of data

rmax - maximum distance

Returns:

function value.

butterworthLowPassFunction

public static final double butterworthLowPassFunction(int n,
                                                      double radius,
                                                      double r)

Computes the transfer function for a Butterworth low pass filter.

Parameters:

n - order of filter

radius - filter radius

r - distance from centre of spectrum

Returns:

transfer function value.

butterworthHighPassFunction

public static final double butterworthHighPassFunction(int n,
                                                       double radius,
                                                       double r)

Computes the transfer function for a Butterworth high pass filter.

Parameters:

n - order of filter

radius - filter radius

r - distance from centre of spectrum

Returns:

transfer function value.

butterworthBandPassFunction

public static final double butterworthBandPassFunction(int n,
                                                       double radius,
                                                       double delta,
                                                       double r)

Computes the transfer function for a Butterworth band pass filter.

Parameters:

n - order of filter

radius - filter radius

delta - band width

r - distance from centre of spectrum

Returns:

transfer function value.

butterworthBandStopFunction

public static final double butterworthBandStopFunction(int n,
                                                       double radius,
                                                       double delta,
                                                       double r)

Computes the transfer function of a Butterworth band stop filter.

Parameters:

n - order of filter

radius - filter radius

delta - band width

r - distance from centre of spectrum

Returns:

transfer function value.

getWidth

public int getWidth()

Returns:

width of FFT.

getHeight

public int getHeight()

Returns:

height of FFT.

getWindow

public int getWindow()

Returns:

current windowing function.

isSpectral

public boolean isSpectral()

Returns:

true if data are spectral, false if data are spatial.

toString

public java.lang.String toString()

Returns:

information string for an ImageFFT object.

Overrides:

toString in class java.lang.Object

transform

public void transform()

Transforms data via a forward or inverse FFT, as appropriate. An inverse transform is computed if the previous transform was in the forward direction; otherwise, the forward transform is computed.

toImage

public java.awt.image.BufferedImage toImage(java.awt.image.BufferedImage image)
                                     throws FFTException

Converts stored data into an image.

Parameters:

image - destination image, or null

Returns:

FFT data as an image.

Throws:

FFTException - if the data are in spectral form; an image can be created only from data in the spatial domain.

toImage

public java.awt.image.BufferedImage toImage(java.awt.image.BufferedImage image,
                                            int bias)
                                     throws FFTException

Converts stored data into an image.

Parameters:

image - destination image, or null

bias - constant value added to data

Returns:

FFT data as an image.

Throws:

FFTException - if the data are in spectral form; an image can be created only from data in the spatial domain.

getSpectrum

public java.awt.image.BufferedImage getSpectrum()
                                         throws FFTException

Returns the amplitude spectrum of an image, as another image. The data are shifted such that the DC component is at the image centre, and scaled logarithmically so that low-amplitude detail is visible.

Returns:

shifted spectrum, as an image.

Throws:

FFTException - if spectral data are not available (e.g. because last transform was in the inverse direction).

getUnshiftedSpectrum

public java.awt.image.BufferedImage getUnshiftedSpectrum()
                                                  throws FFTException

Returns the amplitude spectrum of an image, as another image. The data are unshifted and are scaled logarithmically so that low-amplitude detail is visible.

Returns:

unshifted spectrum, as an image.

Throws:

FFTException - if spectral data are not available e.g. because last transform was in the inverse direction).

getMagnitude

public float getMagnitude(int u,
                          int v)
                   throws FFTException

Computes magnitude for any point in the spectrum.

Parameters:

u - horizontal spatial frequency

v - vertical spatial frequency

Returns:

magnitude at the specified point, or zero if point does not exist.

Throws:

FFTException - if spectral data are not available.

getPhase

public float getPhase(int u,
                      int v)
               throws FFTException

Computes phase for any point in the spectrum.

Parameters:

u - horizontal spatial frequency

v - vertical spatial frequency

Returns:

phase at the specified point, or zero if point does not exist.

Throws:

FFTException - if spectral data are not available.

setMagnitude

public void setMagnitude(int u,
                         int v,
                         float mag)
                  throws FFTException

Modifies magnitude at any point in the spectrum.

Parameters:

u - horizontal spatial frequency

v - vertical spatial frequency

mag - new magnitiude for specified point

Throws:

FFTException - if spectral data are not available.

setPhase

public void setPhase(int u,
                     int v,
                     float phase)
              throws FFTException

Modifies phase at any point in the spectrum.

Parameters:

u - horizontal spatial frequency

v - vertical spatial frequency

phase - new phase for specified point

Throws:

FFTException - if spectral data are not available.

idealLowPassFilter

public void idealLowPassFilter(double radius)
                        throws FFTException

Performs ideal low pass filtering on the spectrum.

Parameters:

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter radius is invalid.

idealHighPassFilter

public void idealHighPassFilter(double radius)
                         throws FFTException

Performs ideal high pass filtering on the spectrum.

Parameters:

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter radius is invalid.

idealBandPassFilter

public void idealBandPassFilter(double radius,
                                double delta)
                         throws FFTException

Performs ideal band pass filtering on the spectrum.

Parameters:

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

idealBandStopFilter

public void idealBandStopFilter(double radius,
                                double delta)
                         throws FFTException

Performs ideal band stop filtering on the spectrum.

Parameters:

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthLowPassFilter

public void butterworthLowPassFilter(double radius)
                              throws FFTException

Performs order-1 Butterworth low pass filtering of the spectrum.

Parameters:

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthLowPassFilter

public void butterworthLowPassFilter(int n,
                                     double radius)
                              throws FFTException

Performs Butterworth low pass filtering of the spectrum.

Parameters:

n - order of filter

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthHighPassFilter

public void butterworthHighPassFilter(double radius)
                               throws FFTException

Performs order-1 Butterworth high pass filtering of the spectrum.

Parameters:

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthHighPassFilter

public void butterworthHighPassFilter(int n,
                                      double radius)
                               throws FFTException

Performs Butterworth high pass filtering of the spectrum.

Parameters:

n - order of filter

radius - filter radius

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthBandPassFilter

public void butterworthBandPassFilter(double radius,
                                      double delta)
                               throws FFTException

Performs order-1 Butterworth band pass filtering of the spectrum.

Parameters:

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthBandPassFilter

public void butterworthBandPassFilter(int n,
                                      double radius,
                                      double delta)
                               throws FFTException

Performs Butterworth band pass filtering of the spectrum.

Parameters:

n - order of filter

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthBandStopFilter

public void butterworthBandStopFilter(double radius,
                                      double delta)
                               throws FFTException

Performs order-1 Butterworth band stop filtering of the spectrum.

Parameters:

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.

butterworthBandStopFilter

public void butterworthBandStopFilter(int n,
                                      double radius,
                                      double delta)
                               throws FFTException

Performs Butterworth band stop filtering of the spectrum.

Parameters:

n - order of filter

radius - filter radius

delta - band width

Throws:

FFTException - if spectral data are not available or filter parameters are invalid.