Detects a checkerboard pattern (typically 7x4 inner corners, asymmetric layout recommended) in an image using a cross shaped image filter. More...

#include <FeatureDetector/CheckerboardDetectorCrossFilter.hh>

Collaboration diagram for BIAS::CheckerboardDetectorCrossFilter:

Public Member Functions
	CheckerboardDetectorCrossFilter ()
	Standard constructor. More...

std::vector< HomgPoint2D >	GetCheckerboard (Image< unsigned char > img, int numberOfCols=7, int numberOfRows=4, bool upperLeftIsBlack=true)
	Find a checkerboard of size numberOfCols x numberOfRows in the given image. More...

virtual	~CheckerboardDetectorCrossFilter ()

Static Public Member Functions
static int	Compute (BIAS::Image< unsigned char > &img, const unsigned int &xCorners, const unsigned int &yCorners, t_CoordVecf &coords, const bool &saveDebugImage=false)
	Detects a (recommended asymmetric) checkerboard pattern. More...

Protected Member Functions
bool	doLinesIntersect (HomgPoint2D &a, HomgPoint2D &b, HomgPoint2D &c, HomgPoint2D &d)
	Check if the finite lines a - b and c - d intersect. More...

void	ExtendTopology (Image< unsigned char > &img, std::vector< HomgPoint2D > &knotPositions, std::deque< std::deque< int > > &rectTopolog)
	Find the side of the rectangular topology which is most likely not on the edge of the checkerboard and extend the checkerboard to it. More...

void	GenerateRectangularTopology (Image< unsigned char > &img, std::vector< HomgPoint2D > &knotPositions, std::vector< std::vector< int > > &adjacence, std::deque< std::deque< int > > &rectTopolog)
	Generate a rectangular topology out of the adjcence lists. More...

double	getAverage (Image< unsigned char > &img, HomgPoint2D center, int halfWinSize)
	Get the average image grey value (also for color images) in a window. More...

void	GetAvgBlackWhiteValue (Image< unsigned char > &img, std::vector< HomgPoint2D > points, double &avgBlack, double &avgWhite, int angleSteps)
	Calculate the average black and white values of the cross filter at a given set of points. More...

void	GetCCACenter (const std::vector< HomgPoint2D > pixels, std::vector< HomgPoint2D > &centers, int width, int height)
	Calculate a connected components analysis for a given set of pixel coordinates. More...

double	GetCheckerLineFactor (Image< unsigned char > img, HomgPoint2D a, HomgPoint2D b)
	Calculate a fitness value for the line between a and b to be a checkerboard line. More...

void	GetFilterResponseSum (Image< unsigned char > &img, std::vector< HomgPoint2D > &response, float threshold=25000.0, int halfWinSize=20, bool fastMode=true)
	Calculate the filter result for the whole image and return the pixel coordinates above the given threshold. More...

std::vector< HomgPoint2D >	GetFinalCheckerboard (Image< unsigned char > &img, std::vector< HomgPoint2D > &knotPositions, std::deque< std::deque< int > > &rectTopolog, int numberOfRows, int numberOfCols, bool upperLeftIsBlack)
	Analyse the rectangular topology and rotate and flip the checkerboard to its unique representation. More...

HomgPoint2D	lineIntersection (HomgPoint2D &a, HomgPoint2D &b, HomgPoint2D &c, HomgPoint2D &d)
	Calculate the intersection point of the infinite lines a - b and c - d. More...

void	SearchForMissingTopologyEntries (Image< unsigned char > &img, std::vector< HomgPoint2D > &knotPositions, std::deque< std::deque< int > > &rectTopolog)
	Fill the topology entries that are unknown (negative indices) by generating an appropriate knot. More...

void	StretchImageValues (Image< unsigned char > &img, unsigned int from, unsigned int to)
	Stretch the image values such that from => 0 and to => 255. More...

Protected Attributes
int	defaultAngleSteps_
	The default number of rotation stpes performed at each filter evaluation. More...

int	defaultHalfWinSize_
	The default half window size of the filter window. More...

int	initialFilterThreshold_
	The initial value for the filter response threshold for a pixel to be evaluated further. More...

int	initialLineThreshold_
	The initial value for the line threshold in the topology generation. More...

Static Protected Attributes
static CheckerboardDetectorCrossFilter *	instancePointer_ = NULL
	Instance pointer if an instance was created. More...

Detailed Description

Detects a checkerboard pattern (typically 7x4 inner corners, asymmetric layout recommended) in an image using a cross shaped image filter.

Note: This checker board detecter uses a rotating cross filter that sums up the absolute differences between the two lines of that cross along with a symmetry penalty term. In addition, a line fitness based on differences of the line vicinity and homogeneity is used together with a lot of heuristics.

Author: Andreas Jordt

Date: 2010

Definition at line 36 of file CheckerboardDetectorCrossFilter.hh.

Constructor & Destructor Documentation

CheckerboardDetectorCrossFilter::CheckerboardDetectorCrossFilter ( )

Standard constructor.

Definition at line 19 of file CheckerboardDetectorCrossFilter.cpp.

CheckerboardDetectorCrossFilter::~CheckerboardDetectorCrossFilter ( )

virtual

Definition at line 40 of file CheckerboardDetectorCrossFilter.cpp.

Member Function Documentation

int CheckerboardDetectorCrossFilter::Compute	(	BIAS::Image< unsigned char > &	img,
		const unsigned int &	xCorners,
		const unsigned int &	yCorners,
		t_CoordVecf &	coords,
		const bool &	saveDebugImage = `false`
	)

static

Detects a (recommended asymmetric) checkerboard pattern.

Parameters

img	Input image
xCorners	Number of inner checkerboard corners in x direction
yCorners	Number of inner checkerboard corners in y direction
coords	The resulting set of corner coordinates
saveDebugImage	ignored (just for compatibility)

Returns: 0 for success, <0 for error (e.g. could not detect all inner corners).

Definition at line 47 of file CheckerboardDetectorCrossFilter.cpp.

Referenced by BIAS::ImageCanvasCheckerboardExtract::SelectCheckerboardCorners().

bool CheckerboardDetectorCrossFilter::doLinesIntersect	(	HomgPoint2D &	a,
		HomgPoint2D &	b,
		HomgPoint2D &	c,
		HomgPoint2D &	d
	)

protected

Check if the finite lines a - b and c - d intersect.

Definition at line 1159 of file CheckerboardDetectorCrossFilter.cpp.

void CheckerboardDetectorCrossFilter::ExtendTopology	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D > &	knotPositions,
		std::deque< std::deque< int > > &	rectTopolog
	)

protected

Find the side of the rectangular topology which is most likely not on the edge of the checkerboard and extend the checkerboard to it.

Parameters

img	Input image
knotPositions	The image coordinates of the knots
rectTopolog	The rectangular topology of the knots

Definition at line 643 of file CheckerboardDetectorCrossFilter.cpp.

void CheckerboardDetectorCrossFilter::GenerateRectangularTopology	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D > &	knotPositions,
		std::vector< std::vector< int > > &	adjacence,
		std::deque< std::deque< int > > &	rectTopolog
	)

protected

Generate a rectangular topology out of the adjcence lists.

Parameters

img	Input image
knotPositions	The image coordinates of the knots
adjacence	The adjacence list for each knot
rectTopolog	The resulting rectangular output structure

Definition at line 276 of file CheckerboardDetectorCrossFilter.cpp.

double CheckerboardDetectorCrossFilter::getAverage	(	BIAS::Image< unsigned char > &	img,
		BIAS::HomgPoint2D	center,
		int	halfWinSize
	)

protected

Get the average image grey value (also for color images) in a window.

Parameters

img	Input image
center	The center of the square window
halfWinSize	The half size of the square the value is calculated from

Definition at line 1176 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetHeight(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::GetWidth().

void CheckerboardDetectorCrossFilter::GetAvgBlackWhiteValue	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D >	points,
		double &	avgBlack,
		double &	avgWhite,
		int	angleSteps
	)

protected

Calculate the average black and white values of the cross filter at a given set of points.

Parameters

img	Input image
points	The set of positions the filters are evaluated
avgBlack	The resulting average black value
avgWhite	The resulting average white value
angleStep	The number of rotations of the cross filter

Definition at line 78 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetChannelCount(), and BIAS::Image< StorageType >::GetImageDataArray().

void CheckerboardDetectorCrossFilter::GetCCACenter	(	const std::vector< HomgPoint2D >	pixels,
		std::vector< HomgPoint2D > &	centers,
		int	width,
		int	height
	)

protected

Calculate a connected components analysis for a given set of pixel coordinates.

Parameters

pixels	The input pixel coordinates
centers	The centers of weight of the resulting cluster
width	The maximum x component of the input pixels
height	The maximum y component of the input pixels

Definition at line 239 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::BlobDetectorCCA< StorageType >::Detect(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::SetZero().

vector< HomgPoint2D > CheckerboardDetectorCrossFilter::GetCheckerboard	(	Image< unsigned char >	img,
		int	numberOfCols = `7`,
		int	numberOfRows = `4`,
		bool	upperLeftIsBlack = `true`
	)

Find a checkerboard of size numberOfCols x numberOfRows in the given image.

Parameters

img	Input image
numberOfCols	The number of corners on the checkerboard in horizontal direction
numberOfRows	The number of corners on the checkerboard in vertical direction
upperLeftIsBlack	Set true if the field between corners (0,0), (0,1), (1,0) and (1,1) is black

Definition at line 946 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetChannelCount(), BIAS::ImageBase::GetHeight(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::GetWidth().

double CheckerboardDetectorCrossFilter::GetCheckerLineFactor	(	Image< unsigned char >	img,
		HomgPoint2D	a,
		HomgPoint2D	b
	)

protected

Calculate a fitness value for the line between a and b to be a checkerboard line.

Definition at line 1196 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetHeight(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::GetWidth().

void CheckerboardDetectorCrossFilter::GetFilterResponseSum	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D > &	response,
		float	threshold = `25000.0`,
		int	halfWinSize = `20`,
		bool	fastMode = `true`
	)

protected

Calculate the filter result for the whole image and return the pixel coordinates above the given threshold.

Parameters

img	Input image
response	The set of pixels above the threshold
threshold	Filter threshold
halfWinSize	The size of the cross filter
fastMode	speed up the filter search but risk missing some points

Definition at line 133 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetChannelCount(), BIAS::ImageBase::GetHeight(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::GetWidth().

vector< HomgPoint2D > CheckerboardDetectorCrossFilter::GetFinalCheckerboard	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D > &	knotPositions,
		std::deque< std::deque< int > > &	rectTopolog,
		int	numberOfRows,
		int	numberOfCols,
		bool	upperLeftIsBlack
	)

protected

Analyse the rectangular topology and rotate and flip the checkerboard to its unique representation.

Parameters

img	Input image
knotPositions	The image coordinates of the knots
rectTopolog	The rectangular topology
numberOfRows	The expected number of rows of the checkerboard
numberOfCols	The expected number of columns of the checkerboard
upperLeftIsBlack	Set true if the field between corners (0,0), (0,1), (1,0) and (1,1) is black

Definition at line 844 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::Vector3< T >::CrossProduct(), BIAS::ImageBase::GetChannelCount(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::Vector3< T >::size().

HomgPoint2D CheckerboardDetectorCrossFilter::lineIntersection	(	HomgPoint2D &	a,
		HomgPoint2D &	b,
		HomgPoint2D &	c,
		HomgPoint2D &	d
	)

protected

Calculate the intersection point of the infinite lines a - b and c - d.

Definition at line 1169 of file CheckerboardDetectorCrossFilter.cpp.

void CheckerboardDetectorCrossFilter::SearchForMissingTopologyEntries	(	Image< unsigned char > &	img,
		std::vector< HomgPoint2D > &	knotPositions,
		std::deque< std::deque< int > > &	rectTopolog
	)

protected

Fill the topology entries that are unknown (negative indices) by generating an appropriate knot.

Parameters

img	Input image
knotPositions	The image coordinates of the knots
rectTopolog	The rectangular topology

Definition at line 602 of file CheckerboardDetectorCrossFilter.cpp.

void CheckerboardDetectorCrossFilter::StretchImageValues	(	Image< unsigned char > &	img,
		unsigned int	from,
		unsigned int	to
	)

protected

Stretch the image values such that from => 0 and to => 255.

Parameters

img	Input image
from	The value that is pulled to 0
to	The value that is pushed to 255

Definition at line 220 of file CheckerboardDetectorCrossFilter.cpp.

References BIAS::ImageBase::GetHeight(), BIAS::Image< StorageType >::GetImageDataArray(), and BIAS::ImageBase::GetWidth().

Member Data Documentation

int BIAS::CheckerboardDetectorCrossFilter::defaultAngleSteps_

protected

The default number of rotation stpes performed at each filter evaluation.

Definition at line 186 of file CheckerboardDetectorCrossFilter.hh.

int BIAS::CheckerboardDetectorCrossFilter::defaultHalfWinSize_

protected

The default half window size of the filter window.

Definition at line 183 of file CheckerboardDetectorCrossFilter.hh.

int BIAS::CheckerboardDetectorCrossFilter::initialFilterThreshold_

protected

The initial value for the filter response threshold for a pixel to be evaluated further.

Definition at line 189 of file CheckerboardDetectorCrossFilter.hh.

int BIAS::CheckerboardDetectorCrossFilter::initialLineThreshold_

protected

The initial value for the line threshold in the topology generation.

Definition at line 192 of file CheckerboardDetectorCrossFilter.hh.

CheckerboardDetectorCrossFilter * CheckerboardDetectorCrossFilter::instancePointer_ = NULL

staticprotected

Instance pointer if an instance was created.

This hack is needed to stay compatible to the static function calls of the other checkerboard detectors

Definition at line 196 of file CheckerboardDetectorCrossFilter.hh.

The documentation for this class was generated from the following files:

FeatureDetector/CheckerboardDetectorCrossFilter.hh
FeatureDetector/CheckerboardDetectorCrossFilter.cpp

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Static Protected Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation