boofcv.alg.shapes.polyline

Class SplitMergeLineFit

java.lang.Object

boofcv.alg.shapes.polyline.SplitMergeLineFit

Direct Known Subclasses:

SplitMergeLineFitLoop, SplitMergeLineFitSegment

public abstract class SplitMergeLineFit
extends java.lang.Object

Base class for algorithm which employ a split and merge strategy to fitting a set of line segments onto an ordered set of points. The lines are an approximation of the original shape described by the point list. This list can either be connected at the end (looped) or not, depending on the implementation. The points in the list are assumed to be ordered with each consecutive point connected to its neighbors. The output is a set of indexes which correspond to points in the original list that compose the line segments. A minimum of two indexes will be returned. The returned set of line segments is guaranteed to match the original set of points to within a user specified tolerance. That is, no point in the list will be more than 'tol' distance away from a line segment. A line is split when a point between two end points is greater than the split distance. A corner is removed (two lines merged) if the corner is less than the split distance away from two of its adjacent neighbors. The split threshold is specified as a fraction of line distance to maximize scale invariance. The minimum split threshold is specified in units of pixels because a simple ratio doesn't work well for small objects. Split and merge is repeated until there is no more change or the maximum number of iterations has been reached.

Field Summary

Fields

Modifier and Type	Field and Description
protected int	abortSplits
protected org.ddogleg.struct.GrowQueue_B	changed
protected java.util.List<georegression.struct.point.Point2D_I32>	contour
protected georegression.struct.line.LineParametric2D_F64	line
protected int	maxIterations
protected double	minimumSideLengthFraction
protected int	minimumSideLengthPixel
protected georegression.struct.point.Point2D_F64	point2D
protected org.ddogleg.struct.GrowQueue_I32	splits
protected double	toleranceFractionSq
protected org.ddogleg.struct.GrowQueue_I32	work

Constructor Summary

Constructors

Constructor and Description
SplitMergeLineFit(double splitFraction, double minimumSideLengthFraction, int maxIterations) Configures algorithm

Method Summary

Modifier and Type	Method and Description
int	getAbortSplits()
double	getMinimumSideLengthFraction()
org.ddogleg.struct.GrowQueue_I32	getSplits() List of point indexes in the contour.
abstract boolean	process(java.util.List<georegression.struct.point.Point2D_I32> list) Approximates the input list with a set of line segments
void	setAbortSplits(int abortSplits)
void	setMaxIterations(int maxIterations)
void	setMinimumSideLengthFraction(double minimumSideLengthFraction)
void	setSplitFraction(double toleranceSplit)
protected double	splitThresholdSq(georegression.struct.point.Point2D_I32 a, georegression.struct.point.Point2D_I32 b) Computes the split threshold from the end point of two lines

Methods inherited from class java.lang.Object

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

Field Detail

maxIterations

protected int maxIterations

toleranceFractionSq

protected double toleranceFractionSq

minimumSideLengthFraction

protected double minimumSideLengthFraction

minimumSideLengthPixel

protected int minimumSideLengthPixel

contour

protected java.util.List<georegression.struct.point.Point2D_I32> contour

line

protected georegression.struct.line.LineParametric2D_F64 line

point2D

protected georegression.struct.point.Point2D_F64 point2D

splits

protected org.ddogleg.struct.GrowQueue_I32 splits

work

protected org.ddogleg.struct.GrowQueue_I32 work

changed

protected org.ddogleg.struct.GrowQueue_B changed

abortSplits

protected int abortSplits

Constructor Detail

SplitMergeLineFit

public SplitMergeLineFit(double splitFraction,
                         double minimumSideLengthFraction,
                         int maxIterations)

Configures algorithm

Parameters:

splitFraction - A line will be split if a point is more than this fraction of its length away from the line. Try 0.05

minimumSideLengthFraction - The minimum length of a side as a function of contour length

maxIterations - Maximum number of split and merge refinements. Set to zero to disable refinement. Try 20

Method Detail

process

public abstract boolean process(java.util.List<georegression.struct.point.Point2D_I32> list)

Approximates the input list with a set of line segments

Parameters:

list - Ordered list of connected points.

Returns:

true if it could fit a polygon to the points or false if not

splitThresholdSq

protected double splitThresholdSq(georegression.struct.point.Point2D_I32 a,
                                  georegression.struct.point.Point2D_I32 b)

Computes the split threshold from the end point of two lines

getSplits

public org.ddogleg.struct.GrowQueue_I32 getSplits()

List of point indexes in the contour. Each point is the end of a line segment. A minimum of two points will be returned. NOTE: This list is modified the next time process is called.

Returns:

List of indexes

setMaxIterations

public void setMaxIterations(int maxIterations)

setSplitFraction

public void setSplitFraction(double toleranceSplit)

getAbortSplits

public int getAbortSplits()

setAbortSplits

public void setAbortSplits(int abortSplits)

getMinimumSideLengthFraction

public double getMinimumSideLengthFraction()

setMinimumSideLengthFraction

public void setMinimumSideLengthFraction(double minimumSideLengthFraction)