de.unihalle.informatik.MiToBo.fields

Class VectorField2DPotentialFinder

java.lang.Object

de.unihalle.informatik.MiToBo.fields.VectorField2DPotentialFinder

public class VectorField2DPotentialFinder
extends Object

Routines for reconstructing potential from vector field.

Author:

moeller

See Also:

MTBVectorField2D

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	VectorField2DPotentialFinder.PotentialFinderOptFunction Optimization function for gradient-based potential reconstruction.

Field Summary

Fields

Modifier and Type	Field and Description
protected MTBVectorField2D	field Vector field the potential is reconstructed for.

Constructor Summary

Constructors

Constructor and Description
VectorField2DPotentialFinder() Standard constructor.
VectorField2DPotentialFinder(MTBVectorField2D f) Default constructor.

Method Summary

Modifier and Type	Method and Description
double[]	calcPotential_exactLeastSquares(boolean ignoreBorder) Exact least squares reconstruction of the potential.
double[]	calcPotential_gradientDescent(boolean ignoreBorder) Reconstruct potential via gradient descent.
double[]	calcPotential_incrementalLeastSquares(boolean ignoreBorder) Reconstructs the potential of the vector field incrementally.
private void	normalizePotentialToMin(double[] pot, boolean ignoreBorder) Function to normalize a potential to the minimum value of 0.

Methods inherited from class java.lang.Object

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

Field Detail

field

protected MTBVectorField2D field

Vector field the potential is reconstructed for.

Constructor Detail

VectorField2DPotentialFinder

public VectorField2DPotentialFinder()

Standard constructor.

VectorField2DPotentialFinder

public VectorField2DPotentialFinder(MTBVectorField2D f)

Default constructor.

Parameters:

f - Vector field.

Method Detail

calcPotential_exactLeastSquares

public double[] calcPotential_exactLeastSquares(boolean ignoreBorder)

Exact least squares reconstruction of the potential.

Attention!!! This function takes a lot of memory! Never use it with fields larger than approx. 30 x 30 pixels!!!

The function reconstructs the potential by solving a linear system of equations via explicit LQ-decomposition. The linear system contains a lot of rows and columns:

• #cols = number of pixels in the image
• #rows = approx. 2 * number of pixels in the image

As a consequence the function should only be applied to quite small images not exceeding 30 pixels in width or height.

Parameters:

ignoreBorder - If true, first/last column/row of U and V will be ignored.

Returns:

Calculated potential field.

calcPotential_gradientDescent

public double[] calcPotential_gradientDescent(boolean ignoreBorder)

Reconstruct potential via gradient descent.

Parameters:

ignoreBorder - If true, border pixels are ignored in reconstruction.

Returns:

Calculated potential field.

calcPotential_incrementalLeastSquares

public double[] calcPotential_incrementalLeastSquares(boolean ignoreBorder)

Reconstructs the potential of the vector field incrementally.

Starting with last entry field bottom right in the vector field the potential is reconstructed incrementally by least square solutions of the two given constraint equations for each image pixel. The solution is only approximative as no global optimization criterion is considered. Nevertheless, it might be used as initialization for the gradient descent routines, if it is not of direct interest.

Parameters:

ignoreBorder - If true, first/last row/column of U and V are ignored.

normalizePotentialToMin

private void normalizePotentialToMin(double[] pot,
                                     boolean ignoreBorder)

Function to normalize a potential to the minimum value of 0.

Parameters:

pot - Potential field to normalize.

ignoreBorder - If true outer rows and cols are ignored.