net.sf.jaer.eventprocessing.tracking
Class HoughLineTracker

java.lang.Object
  net.sf.jaer.eventprocessing.EventFilter
      net.sf.jaer.eventprocessing.EventFilter2D
          net.sf.jaer.eventprocessing.tracking.HoughLineTracker

All Implemented Interfaces:

java.util.Observer, LineDetector, FrameAnnotater

public class HoughLineTracker
extends EventFilter2D
implements FrameAnnotater, LineDetector, java.util.Observer

Tracks a single line as used for line-following navigation or for lane tracking.

Origin of the line is center of image. Angle of line is 0 when vertical and positive for clockwise line rotation.

The line is tracked using an incremental Hough transform method. See http://rkb.home.cern.ch/rkb/AN16pp/node122.html for a concise explanation of basic idea of Hough's. Or http://en.wikipedia.org/wiki/Hough_transform. Or http://www.cs.tu-bs.de/rob/lehre/bv/HNF.html for a good interactive java applet demo.

Each point is splatted in its p, theta form into an accumulator array; the array maximum value is computed for each packet and the resulting p,theta values are lowpass filtered to form the output.

Author:

tobi

See Also:

LineDetector

Field Summary

Fields inherited from class net.sf.jaer.eventprocessing.EventFilter2D

enclosedFilter, out

Fields inherited from class net.sf.jaer.eventprocessing.EventFilter

annotationEnabled, chip, enclosedFilterChain, filterEnabled, log, perf, propertyTooltipMap, support

Constructor Summary

HoughLineTracker(AEChip chip)
Creates a new instance of LineTracker

Method Summary

void	annotate(float[][][] frame) annotate the RGB frame somehow by color pixels in the rendered pixel frame data.
void	annotate(javax.media.opengl.GLAutoDrawable drawable) Each annotator enters annotate with graphics context current, in coordinates with pixel 0,0 in LL corner (note opposite from Java2D) and pixel spacing 1 unit after the scaling transform (which is already active).
void	annotate(java.awt.Graphics2D g) each annotator is called by the relevant class (e.g.
EventPacket<?>	filterPacket(EventPacket<?> in) Subclasses implement this method to define custom processing.
static java.lang.String	getDescription()
float	getFavorVerticalAngleRangeDeg()
java.lang.Object	getFilterState() should return the filter state in some useful form
float	getHoughDecayFactor()
float	getRhoPixels() returns the Hough line radius of the last packet's estimate - the closest distance from the middle of the chip image.
float	getRhoPixelsFiltered() returns the filtered Hough line radius estimate - the closest distance from the middle of the chip image.
float	getRhoResPixels()
float	getTauMs()
float	getThetaDeg() returns the angle of the last packet's Hough line.
float	getThetaDegFiltered() returns the filtered angle of the line.
float	getThetaRad() returns the angle of the last packet's Hough line.
float	getThetaResDeg()
void	initFilter() this should allocate and initialize memory: it may be called when the chip e.g.
boolean	isShowHoughWindow()
void	resetFilter() should reset the filter to initial state
void	setFavorVerticalAngleRangeDeg(float favorVerticalAngleRangeDeg)
void	setHoughDecayFactor(float houghDecayFactor)
void	setRhoResPixels(float rhoResPixels)
void	setShowHoughWindow(boolean showHoughWindow)
void	setTauMs(float tauMs)
void	setThetaResDeg(float thetaResDeg)
void	update(java.util.Observable o, java.lang.Object arg)

Methods inherited from class net.sf.jaer.eventprocessing.EventFilter2D

checkOutputPacketEventType, checkOutputPacketEventType, getEnclosedFilter, resetOut, setEnclosedFilter, setFilterEnabled

Methods inherited from class net.sf.jaer.eventprocessing.EventFilter

getChip, getEnclosedFilterChain, getEnclosingFilter, getPrefs, getPropertyChangeSupport, getPropertyTooltip, isAnnotationEnabled, isEnclosed, isFilterEnabled, prefsEnabledKey, setAnnotationEnabled, setChip, setEnclosed, setEnclosedFilter, setEnclosedFilterChain, setEnclosingFilter, setPreferredEnabledState, setPrefs, setPropertyTooltip

Methods inherited from class java.lang.Object

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

Methods inherited from interface net.sf.jaer.graphics.FrameAnnotater

isAnnotationEnabled, setAnnotationEnabled

Constructor Detail

HoughLineTracker

public HoughLineTracker(AEChip chip)

Creates a new instance of LineTracker

Parameters:

chip - the chip to track for

Method Detail

getDescription

public static java.lang.String getDescription()

getRhoPixels

public float getRhoPixels()

returns the Hough line radius of the last packet's estimate - the closest distance from the middle of the chip image.

Returns:

the distance in pixels. If the chip size is sx by sy, can range over +-Math.sqrt( (sx/2)^2 + (sy/2)^2). This number is positive if the line is above the origin (center of chip)

getThetaDeg

public float getThetaDeg()

returns the angle of the last packet's Hough line.

Returns:

angle in degrees. Ranges from 0 to 180 degrees, where 0 and 180 represent a vertical line and 90 is a horizontal line

getThetaRad

public float getThetaRad()

returns the angle of the last packet's Hough line.

Returns:

angle in radians. Ranges from 0 to Pi radians, where 0 and Pi represent a vertical line and Pi/2 is a horizontal line

resetFilter

public void resetFilter()

Description copied from class: EventFilter

should reset the filter to initial state

Specified by:

resetFilter in class EventFilter

filterPacket

public EventPacket<?> filterPacket(EventPacket<?> in)

Description copied from class: EventFilter2D

Subclasses implement this method to define custom processing.

Specified by:

filterPacket in class EventFilter2D

Parameters:

in - the input packet

Returns:

the output packet

annotate

public void annotate(javax.media.opengl.GLAutoDrawable drawable)

Description copied from interface: FrameAnnotater

Each annotator enters annotate with graphics context current, in coordinates with pixel 0,0 in LL corner (note opposite from Java2D) and pixel spacing 1 unit after the scaling transform (which is already active). The FrameAnnotater then can use JOGL calls to render to the screen by getting the GL context, e.g. the following code, used in the context of an AEChip object, draws a golden lines from LL to UR of the pixel array.

        GL gl = drawable.getGL();
        gl.glBegin(GL.GL_LINES);
        gl.glColor3f(.5f, .5f, 0);
        gl.glVertex2f(0, 0);
        gl.glVertex2f(getSizeX() - 1, getSizeY() - 1);
        gl.glEnd();
 

Specified by:

annotate in interface FrameAnnotater

Parameters:

drawable - the OpenGL drawable components, e.g., GLCanvas

getFilterState

public java.lang.Object getFilterState()

Description copied from class: EventFilter

should return the filter state in some useful form

Specified by:

getFilterState in class EventFilter

initFilter

public void initFilter()

Description copied from class: EventFilter

this should allocate and initialize memory: it may be called when the chip e.g. size parameters are changed after creation of the filter

Specified by:

initFilter in class EventFilter

annotate

public void annotate(float[][][] frame)

Description copied from interface: FrameAnnotater

annotate the RGB frame somehow by color pixels in the rendered pixel frame data.

Specified by:

annotate in interface FrameAnnotater

Parameters:

frame - the RGB pixel information. First dimension is Y, second is X, third is RGB

annotate

public void annotate(java.awt.Graphics2D g)

Description copied from interface: FrameAnnotater

each annotator is called by the relevant class (e.g. EyeTracker) and enters annotate with graphics context current, in coordinates with pixel 0,0 in UL corner and pixel spacing 1 unit before scaling transform (which is already active).

Specified by:

annotate in interface FrameAnnotater

Parameters:

g - the Graphics2D context

getThetaResDeg

public float getThetaResDeg()

setThetaResDeg

public void setThetaResDeg(float thetaResDeg)

getRhoResPixels

public float getRhoResPixels()

setRhoResPixels

public void setRhoResPixels(float rhoResPixels)

getTauMs

public float getTauMs()

setTauMs

public void setTauMs(float tauMs)

isShowHoughWindow

public boolean isShowHoughWindow()

setShowHoughWindow

public void setShowHoughWindow(boolean showHoughWindow)

getRhoPixelsFiltered

public float getRhoPixelsFiltered()

returns the filtered Hough line radius estimate - the closest distance from the middle of the chip image.

Specified by:

getRhoPixelsFiltered in interface LineDetector

Returns:

the distance in pixels. If the chip size is sx by sy, can range over +-Math.sqrt( (sx/2)^2 + (sy/2)^2). This number is positive if the line is above the origin (center of chip)

getThetaDegFiltered

public float getThetaDegFiltered()

returns the filtered angle of the line.

Specified by:

getThetaDegFiltered in interface LineDetector

Returns:

angle in degrees. Ranges from 0 to 180 degrees, where 0 and 180 represent a vertical line and 90 is a horizontal line

update

public void update(java.util.Observable o,
                   java.lang.Object arg)

Specified by:

update in interface java.util.Observer

getFavorVerticalAngleRangeDeg

public float getFavorVerticalAngleRangeDeg()

setFavorVerticalAngleRangeDeg

public void setFavorVerticalAngleRangeDeg(float favorVerticalAngleRangeDeg)

getHoughDecayFactor

public float getHoughDecayFactor()

setHoughDecayFactor

public void setHoughDecayFactor(float houghDecayFactor)