FlowJ
Class FlowJLucas

java.lang.Object
  |
  +--FlowJ.FlowJLucas

public class FlowJLucas

extends java.lang.Object

This is a class that implements the Lucas and Kanade optical flow algorithm. Implementation based on convolutions, with local field properties, gradient computation with different kernels including scalable Gaussian derivatives.

 References:
      Lucas and Kanade, Proc IJNA 1981
      Barron, Fleet, Beauchemin, 1994, IJCV 12, 1, 43-77
      Abramoff et al, 2002, IEEE TMI.
 

Copyright (c) 1999-2002, Michael Abramoff. All rights reserved.

Field Summary

protected static int	CENTRALDIFF
boolean	debug
protected float	density
boolean	displayon
protected VolumeFloat	dt
protected VolumeFloat	dx
protected VolumeFloat	dy
protected Kernel	G
protected static int	GAUSSIANDERIV Types of derivative computation.
protected Kernel	gradientKernel
protected boolean	includeNormals
protected int	REG_AVERAGE
protected int	REG_GAUSSIAN
protected int	REG_GAUSSIAN_1D Types of regularization (smoothness constraint) computation.
static java.lang.String[]	sderiv
protected Kernel1D	sgradientKernel
protected Kernel1D	sKernel
protected static int	SOBEL2D
protected static int	SOBEL3D
static java.lang.String[]	sregul
protected static int	SUBTRACT
protected int	support
protected float	tau
protected Kernel1D	tgradientKernel
protected Kernel1D	tKernel

Constructor Summary

FlowJLucas()

Method Summary

void	computeFull(FlowJFlow flow, boolean includeNormals, float sigmaw, float tau, int regularizationMethod) Compute full flow field from the first order gradients in dx, dy, dt for a weighted local neighborhood omega (weighted by G defined by sigmaw) around every image location.
void	filterAll(ij.ImageStack is, int center, float sigmat, float sigmas, int gradientType) Do filtering.
static int	firstFrame(ij.ImageStack is, float sigmat, int gradientType) Return the first frame for which you can compute the flow.
static int	getSupport(float sigmat, int gradientType) Return the number of frames needed for specific sigmat and gradient type.
static int	lastFrame(ij.ImageStack is, float sigmat, int gradientType) Return the last frame for which you can compute the flow.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

debug

public final boolean debug

displayon

public final boolean displayon

GAUSSIANDERIV

protected static final int GAUSSIANDERIV

Types of derivative computation.

CENTRALDIFF

protected static final int CENTRALDIFF

SOBEL2D

protected static final int SOBEL2D

SOBEL3D

protected static final int SOBEL3D

SUBTRACT

protected static final int SUBTRACT

sderiv

public static java.lang.String[] sderiv

tau

protected float tau

sKernel

protected Kernel1D sKernel

tKernel

protected Kernel1D tKernel

gradientKernel

protected Kernel gradientKernel

sgradientKernel

protected Kernel1D sgradientKernel

tgradientKernel

protected Kernel1D tgradientKernel

G

protected Kernel G

density

protected float density

dx

protected VolumeFloat dx

dy

protected VolumeFloat dy

dt

protected VolumeFloat dt

REG_GAUSSIAN_1D

protected final int REG_GAUSSIAN_1D

Types of regularization (smoothness constraint) computation.

REG_GAUSSIAN

protected final int REG_GAUSSIAN

REG_AVERAGE

protected final int REG_AVERAGE

sregul

public static java.lang.String[] sregul

support

protected int support

includeNormals

protected boolean includeNormals

Constructor Detail

FlowJLucas

public FlowJLucas()

Method Detail

getSupport

public static int getSupport(float sigmat,
                             int gradientType)

Return the number of frames needed for specific sigmat and gradient type.

Parameters:

sigmat - temporal sigma of the kernel.

gradientType - the type of gradient, one of GAUSSIANDERIV, CENTRALDIFF, SOBEL2D, SOBEL3D, SUBTRACT

Returns:

number of frames needed.

firstFrame

public static int firstFrame(ij.ImageStack is,
                             float sigmat,
                             int gradientType)

Return the first frame for which you can compute the flow.

Parameters:

is - an ImageStack containing the images.

sigmat - temporal sigma of the kernel.

gradientType - the type of gradient, one of GAUSSIANDERIV, CENTRALDIFF, SOBEL2D, SOBEL3D, SUBTRACT

lastFrame

public static int lastFrame(ij.ImageStack is,
                            float sigmat,
                            int gradientType)

Return the last frame for which you can compute the flow.

Parameters:

is - an ImageStack containing the images.

sigmat - temporal sigma of the kernel.

gradientType - the type of gradient, one of GAUSSIANDERIV, CENTRALDIFF, SOBEL2D, SOBEL3D, SUBTRACT

filterAll

public void filterAll(ij.ImageStack is,
                      int center,
                      float sigmat,
                      float sigmas,
                      int gradientType)
               throws FlowJException

Do filtering.

computeFull

public void computeFull(FlowJFlow flow,
                        boolean includeNormals,
                        float sigmaw,
                        float tau,
                        int regularizationMethod)

Compute full flow field from the first order gradients in dx, dy, dt for a weighted local neighborhood omega (weighted by G defined by sigmaw) around every image location. Find the best fit for that location using a LSE using the pseudoinverse. A SVD decreased speed and did not influence errors. All elements with eigenvalues of the pseudoinverse matrix m smaller than threshold tau are rejected. Only if the second eigenvalue of the pseudoinverse is larger than tau, normal flow instead of full flow is computed for that location.

Parameters:

flow - will contain the x,y flows.

includeNormals - a flag whether to include normals or not.

sigmaw - SD of the probability function associated with the Gaussian defining the size of the neighborhood

tau - the eigenvalue threshold

regularizationMethod - is one of REG_GAUSSIAN, REG_GAUSSIAN_1D, 0 defines how the local neighborhood is filtered.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object