org.openimaj.image.feature.local.detector.pyramid

Class AbstractOctaveExtremaFinder<OCTAVE extends GaussianOctave<FImage>>

java.lang.Object

org.openimaj.image.feature.local.detector.pyramid.AbstractOctaveInterestPointFinder<OCTAVE,FImage>

org.openimaj.image.feature.local.detector.pyramid.AbstractOctaveExtremaFinder<OCTAVE>

Type Parameters:

OCTAVE -

All Implemented Interfaces:

OctaveProcessor<OCTAVE,FImage>, OctaveInterestPointFinder<OCTAVE,FImage>

Direct Known Subclasses:

BasicOctaveExtremaFinder

public abstract class AbstractOctaveExtremaFinder<OCTAVE extends GaussianOctave<FImage>>
extends AbstractOctaveInterestPointFinder<OCTAVE,FImage>

Class for finding extrema within Octaves using the approach in Section 4 of Lowe's IJCV paper (minus the bit on using Brown's interpolation approach to improve localisation).

Interest points are detected if:

• They are at a local extremum in scale-space
• The ratio of the Eigenvalues of the edge response at the point is above a threshold (i.e. the point is not on a straight line, and has a certain amount of curvature).

The AbstractOctaveExtremaFinder uses an event listener paradigm. Once interest points are found, the internal listener will be informed.

Author:

Jonathon Hare (jsh2@ecs.soton.ac.uk)

Field Summary

Fields

Modifier and Type	Field and Description
static float	DEFAULT_EIGENVALUE_RATIO The default threshold for the edge response Eigenvalue ratio
protected float	eigenvalueRatio

Fields inherited from class org.openimaj.image.feature.local.detector.pyramid.AbstractOctaveInterestPointFinder

currentScaleIndex, listener, octave

Constructor Summary

Constructors

Constructor and Description
AbstractOctaveExtremaFinder() Construct an AbstractOctaveExtremaFinder with the default Eigenvalue ratio threshold.
AbstractOctaveExtremaFinder(float eigenvalueRatio) Construct an AbstractOctaveExtremaFinder with the given Eigenvalue ratio threshold.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	beforeProcess(OCTAVE octave) Called at the start of AbstractOctaveExtremaFinder#process(OCTAVE)
protected boolean	firstCheck(float val, int x, int y, int scaleIndex, FImage[] images) Perform the first of the checks that determine whether a point is a valid interest point.
int	getCurrentScaleIndex() Get the current scale index within the octave.
OCTAVE	getOctave() Get the octave from which we are operating
protected boolean	isLocalExtremum(float val, FImage image, int x, int y) Test to see if a point is a local extremum by searching the +/- 1 pixel neighbourhood in x and y.
protected boolean	isNotEdge(FImage image, int x, int y) Test if the pixel at x,y in the image is NOT on an edge.
void	process(OCTAVE octave) Process the provided octave.
protected abstract void	processExtrema(FImage[] images, int s, int x, int y, float octSize) Perform any additional checks on the point, and then inform the listener that a point has been found.

Methods inherited from class org.openimaj.image.feature.local.detector.pyramid.AbstractOctaveInterestPointFinder

getOctaveInterestPointListener, setOctaveInterestPointListener

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_EIGENVALUE_RATIO

public static final float DEFAULT_EIGENVALUE_RATIO

The default threshold for the edge response Eigenvalue ratio

See Also:

Constant Field Values

eigenvalueRatio

protected float eigenvalueRatio

Constructor Detail

AbstractOctaveExtremaFinder

public AbstractOctaveExtremaFinder()

Construct an AbstractOctaveExtremaFinder with the default Eigenvalue ratio threshold.

AbstractOctaveExtremaFinder

public AbstractOctaveExtremaFinder(float eigenvalueRatio)

Construct an AbstractOctaveExtremaFinder with the given Eigenvalue ratio threshold.

Parameters:

eigenvalueRatio -

Method Detail

getOctave

public OCTAVE getOctave()

Description copied from interface: OctaveInterestPointFinder

Get the octave from which we are operating

Specified by:

getOctave in interface OctaveInterestPointFinder<OCTAVE extends GaussianOctave<FImage>,FImage>

Overrides:

getOctave in class AbstractOctaveInterestPointFinder<OCTAVE extends GaussianOctave<FImage>,FImage>

Returns:

the octave

getCurrentScaleIndex

public int getCurrentScaleIndex()

Description copied from interface: OctaveInterestPointFinder

Get the current scale index within the octave. Index 0 is the first level of the octave.

Specified by:

getCurrentScaleIndex in interface OctaveInterestPointFinder<OCTAVE extends GaussianOctave<FImage>,FImage>

Overrides:

getCurrentScaleIndex in class AbstractOctaveInterestPointFinder<OCTAVE extends GaussianOctave<FImage>,FImage>

Returns:

the current scale index.

process

public void process(OCTAVE octave)

Description copied from interface: OctaveProcessor

Process the provided octave.

Parameters:

octave - the octave.

firstCheck

protected boolean firstCheck(float val,
                 int x,
                 int y,
                 int scaleIndex,
                 FImage[] images)

Perform the first of the checks that determine whether a point is a valid interest point. This can be overridden to allow for cheaper tests to occur before more expensive ones.

Parameters:

val - the value at the point.

x - the x-coordinate of the point.

y - the y-coordinate of the point.

scaleIndex - the scale index at which the point was found

images - the scale images

Returns:

true if the point is potentially an interest point; false otherwise.

beforeProcess

protected void beforeProcess(OCTAVE octave)

Called at the start of AbstractOctaveExtremaFinder#process(OCTAVE)

Parameters:

octave - the octave being processed

isLocalExtremum

protected boolean isLocalExtremum(float val,
                      FImage image,
                      int x,
                      int y)

Test to see if a point is a local extremum by searching the +/- 1 pixel neighbourhood in x and y.

Parameters:

val - the value at x,y

image - the image to test against

x - the x-coordinate

y - the y-coordinate

Returns:

true if extremum, false otherwise.

isNotEdge

protected boolean isNotEdge(FImage image,
                int x,
                int y)

Test if the pixel at x,y in the image is NOT on an edge.

Parameters:

image - the image

x - the x-coordinate

y - the y-coordinate

Returns:

true if the pixel is not an edge, false otherwise

processExtrema

protected abstract void processExtrema(FImage[] images,
                  int s,
                  int x,
                  int y,
                  float octSize)

Perform any additional checks on the point, and then inform the listener that a point has been found.

Parameters:

images - the stack of images in this octave

s - the interest-point scale

x - the x-coordinate of the interest-point

y - the y-coordinate of the interest-point

octSize -