imagingbook.pub.hough

Class HoughTransformLinesPosRadius

java.lang.Object

imagingbook.pub.hough.HoughTransformLinesPosRadius

public class HoughTransformLinesPosRadius
extends Object

This class implements the Hough Transform for straight lines. MODIFIED PARAMETER SPACE (no negative RADIUS)!

Version:

2015/11/13

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	HoughTransformLinesPosRadius.HoughLine This class represents a straight line in Hessian normal form, i.e., x * cos(angle) + y * sin(angle) = radius.
static class	HoughTransformLinesPosRadius.Parameters

Constructor Summary

Constructors

Constructor and Description
HoughTransformLinesPosRadius(ij.process.ImageProcessor I, HoughTransformLinesPosRadius.Parameters params) Creates a new Hough transform from the image I.
HoughTransformLinesPosRadius(Point2D[] points, int M, int N, HoughTransformLinesPosRadius.Parameters params) Creates a new Hough transform from a list of 2D points.

Method Summary

Modifier and Type	Method and Description
double	angleFromIndex(int i) Calculates the actual angle (in radians) for angle index ai
int	closestRadialIndex(double r)
int[][]	getAccumulator()
ij.process.FloatProcessor	getAccumulatorImage() Creates and returns an image of the 2D accumulator array.
int[][]	getAccumulatorMax()
ij.process.FloatProcessor	getAccumulatorMaxImage() Creates and returns an image of the local maxima of the 2D accumulator array.
HoughTransformLinesPosRadius.HoughLine[]	getLines(int amin, int maxLines) Finds and returns the parameters of the strongest lines with a specified min.
int	getnAng()
int	getnRad()
Point2D	getReferencePoint()
double	radiusFromIndex(int j) Calculates the actual radius for radius index ri.

Methods inherited from class java.lang.Object

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

Constructor Detail

HoughTransformLinesPosRadius

public HoughTransformLinesPosRadius(ij.process.ImageProcessor I,
                                    HoughTransformLinesPosRadius.Parameters params)

Creates a new Hough transform from the image I.

Parameters:

I - input image, relevant (edge) points have pixel values greater 0.

params - parameter object.

HoughTransformLinesPosRadius

public HoughTransformLinesPosRadius(Point2D[] points,
                                    int M,
                                    int N,
                                    HoughTransformLinesPosRadius.Parameters params)

Creates a new Hough transform from a list of 2D points. Parameters M, N are only used to specify the reference point (usually at the center of the image). Use this constructor if the relevant image points are collected separately.

Parameters:

points - an array of 2D points.

M - width of the corresponding image plane.

N - height of the corresponding image plane.

params - parameter object.

Method Detail

getnRad

public int getnRad()

getnAng

public int getnAng()

getLines

public HoughTransformLinesPosRadius.HoughLine[] getLines(int amin,
                                                         int maxLines)

Finds and returns the parameters of the strongest lines with a specified min. pixel count. All objects in the returned array are valid, but the array may be empty. Note: Could perhaps be implemented more efficiently with insert-sort.

Parameters:

amin - the minimum accumulator value for each line.

maxLines - maximum number of (strongest) lines to extract.

Returns:

a possibly empty array of HoughTransformLinesPosRadius.HoughLine objects.

getReferencePoint

public Point2D getReferencePoint()

Returns:

The reference point used by this Hough transform.

angleFromIndex

public double angleFromIndex(int i)

Calculates the actual angle (in radians) for angle index ai

Parameters:

i - angle index [0,...,nAng-1]

Returns:

Angle [0,...,PI] for angle index ai

radiusFromIndex

public double radiusFromIndex(int j)

Calculates the actual radius for radius index ri.

Parameters:

j - radius index [0,...,nRad-1].

Returns:

Radius [-maxRad,...,maxRad] with respect to reference point (xc, yc).

getAccumulator

public int[][] getAccumulator()

getAccumulatorMax

public int[][] getAccumulatorMax()

getAccumulatorImage

public ij.process.FloatProcessor getAccumulatorImage()

Creates and returns an image of the 2D accumulator array.

Returns:

A FloatProcessor (since accumulator values may be large).

getAccumulatorMaxImage

public ij.process.FloatProcessor getAccumulatorMaxImage()

Creates and returns an image of the local maxima of the 2D accumulator array.

Returns:

A FloatProcessor (since accumulator values may be large).

closestRadialIndex

public int closestRadialIndex(double r)