This class implements the Marching Squares algorithm to find isolines on 2D image slices. More...

#include <CSOMarchingSquares.h>

Classes
struct	AmbiguousCell
	This structure stores an ambiguous cell for a later resolving. More...
Public Types
typedef std::map< int, AmbiguousCell >	mapAmbigousCell
	A map of ambiguous cell for a fast look-up.
typedef mapAmbigousCell::iterator	mapAmbigousCellIter
	An iterator for the map of ambiguous cells.
typedef std::map< int, CSOMarchingSquaresCell >	mapCell
	A map of all cells for a fast look-up.
typedef mapCell::iterator	mapCellIter
	An iterator for the map of cells.
Public Member Functions
	CSOMarchingSquares ()
	Constructor.
	~CSOMarchingSquares ()
	Destructor.
void	reset ()
	Resets the state of the object.
void	setInterpolation (bool use)
	Specifies whether the algorithm should interpolate the contour bi-linearly.
void	setImage (float *image, int imgSizeX, int imgSizeY)
	Sets the 2D image to track/find contours on.
void	setFunction (CSOFunction *implicitFunction, const Matrix4 &voxelToWorldMatrix, int startX, int startY, int imgSizeX, int imgSizeY, int voxelZPosition)
	Sets a 3D interpolation function, an image size and voxel size and a fixed z-offset.
void	findIsoLine (int startPosX, int startPosY, float isoValue, bool takeShortestPath, CSOMarchingSquaresCell::vecPoint2D &positions)
	Looks for an isoline on the `image`.
void	findAllIsoLines (float isoValue, bool takeShortestPath, std::vector< CSOMarchingSquaresCell::vecPoint2D > &vecPositions)
	Finds all contours on the `image` with isovalue `isovalue`. Returns them in a vector of 2D position vectors.
bool	fillCSO (CSO cso, CSOMarchingSquaresCell::vecPoint2D &positions, float posZ, PagedImage pImg, bool useSmoothing, float smoothingFactor, int numSmoothPasses, int smoothRange, CSOSmoothingModes smoothingMode) const
	Fills the given CSO with seedpoints according to the given list of points.
Protected Member Functions
void	_findStartPosition (int &startX, int &startY)
	Searches for a starting position such that startX/startY make up the top-left voxel position of a cell which is intersected by the isoline.
bool	_findNearestIsoCell (int voxelPosX, int voxelPosY, CSOMarchingSquaresCell &cell)
	Searches for the first cell that is an iso cell starting from [`voxelPosX`, `voxelPosY`]. Returns true if a cell was found, i.e. `cell` is valid.
bool	_findNearestIsoCell (int voxelPos[2], CSOMarchingSquaresCell &cell)
	Searches for the first cell that is an iso cell starting from [`voxelPos`[0], `voxelPos`[1]]. Returns true if a cell was found, i.e. `cell` is valid.
void	_trackIsoCell (CSOMarchingSquaresCell startCell, int fromDir, CSOMarchingSquaresCell::vecPoint2D &positions, mapCell *pVisitedCells=NULL)
	Tracks the isoline starting from the `startCell`.
void	_createCell (int topLeftVoxel[2], CSOMarchingSquaresCell &cell)
	Create a new cell at position `topLeftVoxel`[2].
int	_walkToCell (const CSOMarchingSquaresCell &fromCell, int fromDir, CSOMarchingSquaresCell &toCell)
	Create a cell `toCell` from the cell `fromCell` coming from `fromDir`.
int	_getPossibleEnterDirection (const CSOMarchingSquaresCell &cell) const
unsigned int	_getKey (const CSOMarchingSquaresCell &cell) const
	Returns the key for a cell. E.g. for hashtables.
unsigned int	_getKey (int x, int y) const
	Returns the key for a position for hashtables.
float	_getValueAt (int x, int y)
	Returns the value of the image or function at the given position.
Protected Attributes
float *	_image
	Pointer to input image.
int	_imageSizeX
	The x extent of the input image.
int	_imageSizeY
	The y extent of the input image.
int	_startX
	Starting voxel x (function).
int	_startY
	Starting voxel y (function).
float	_isoValue
	The iso value to find the iso line for.
CSOFunction *	_function
	An implicit function.
int	_voxelZPosition
	The z-position of the voxels.
Matrix4	_voxelToWorldMatrix
	The voxelToWorld matrix.
bool	_bInterpolatePoints
	Should the contour be interpolated bi-linearly?
mapAmbigousCell	_mapAmbiguities
	A map holding all ambiguity cells found during traversal.
std::map< int, double >	_existingValues
	A map holding all computed image/function values.

Detailed Description

This class implements the Marching Squares algorithm to find isolines on 2D image slices.

One can either find an iso line starting from a start point or find all contours on that slice.

Definition at line 25 of file CSOMarchingSquares.h.

Member Typedef Documentation

typedef std::map<int, AmbiguousCell> ml::CSOMarchingSquares::mapAmbigousCell

A map of ambiguous cell for a fast look-up.

Definition at line 42 of file CSOMarchingSquares.h.

typedef mapAmbigousCell::iterator ml::CSOMarchingSquares::mapAmbigousCellIter

An iterator for the map of ambiguous cells.

Definition at line 43 of file CSOMarchingSquares.h.

typedef std::map<int, CSOMarchingSquaresCell> ml::CSOMarchingSquares::mapCell

A map of all cells for a fast look-up.

Definition at line 45 of file CSOMarchingSquares.h.

typedef mapCell::iterator ml::CSOMarchingSquares::mapCellIter

An iterator for the map of cells.

Definition at line 46 of file CSOMarchingSquares.h.

Constructor & Destructor Documentation

ml::CSOMarchingSquares::CSOMarchingSquares ( )

Constructor.

ml::CSOMarchingSquares::~CSOMarchingSquares ( )

Destructor.

Member Function Documentation

void ml::CSOMarchingSquares::_createCell	(	int	topLeftVoxel[2],
		CSOMarchingSquaresCell &	cell
	)		`[protected]`

Create a new cell at position topLeftVoxel[2].

bool ml::CSOMarchingSquares::_findNearestIsoCell	(	int	voxelPos[2],
		CSOMarchingSquaresCell &	cell
	)		`[protected]`

Searches for the first cell that is an iso cell starting from [voxelPos[0], voxelPos[1]]. Returns true if a cell was found, i.e. cell is valid.

bool ml::CSOMarchingSquares::_findNearestIsoCell	(	int	voxelPosX,
		int	voxelPosY,
		CSOMarchingSquaresCell &	cell
	)		`[protected]`

Searches for the first cell that is an iso cell starting from [voxelPosX, voxelPosY]. Returns true if a cell was found, i.e. cell is valid.

void ml::CSOMarchingSquares::_findStartPosition	(	int &	startX,
		int &	startY
	)		`[protected]`

Searches for a starting position such that startX/startY make up the top-left voxel position of a cell which is intersected by the isoline.

unsigned int ml::CSOMarchingSquares::_getKey	(	int	x,
		int	y
	)		const `[inline, protected]`

Returns the key for a position for hashtables.

Definition at line 189 of file CSOMarchingSquares.h.

unsigned int ml::CSOMarchingSquares::_getKey ( const CSOMarchingSquaresCell & cell ) const [inline, protected]

Returns the key for a cell. E.g. for hashtables.

Definition at line 182 of file CSOMarchingSquares.h.

References ml::CSOMarchingSquaresCell::_topLeftVoxel.

int ml::CSOMarchingSquares::_getPossibleEnterDirection ( const CSOMarchingSquaresCell & cell ) const [inline, protected]

Returns:: A start direction from which one can enter the created cell.

Definition at line 196 of file CSOMarchingSquares.h.

References ml::CSOMarchingSquaresCell::getToDirection().

float ml::CSOMarchingSquares::_getValueAt	(	int	x,
		int	y
	)		`[protected]`

Returns the value of the image or function at the given position.

void ml::CSOMarchingSquares::_trackIsoCell	(	CSOMarchingSquaresCell	startCell,
		int	fromDir,
		CSOMarchingSquaresCell::vecPoint2D &	positions,
		mapCell *	pVisitedCells = `NULL`
	)		`[protected]`

Tracks the isoline starting from the startCell.

If this is not an iso-cell (i.e. the isoline intersects this cell) it just returns. One can optionally pass a map where to save all visited cells.

int ml::CSOMarchingSquares::_walkToCell	(	const CSOMarchingSquaresCell &	fromCell,
		int	fromDir,
		CSOMarchingSquaresCell &	toCell
	)		`[protected]`

Create a cell toCell from the cell fromCell coming from fromDir.

So this method first looks for the direction leaving the fromCell coming from the direction fromDir.

Returns:: The direction from which one enters the toCell

bool ml::CSOMarchingSquares::fillCSO	(	CSO *	cso,
		CSOMarchingSquaresCell::vecPoint2D &	positions,
		float	posZ,
		PagedImage *	pImg,
		bool	useSmoothing,
		float	smoothingFactor,
		int	numSmoothPasses,
		int	smoothRange,
		CSOSmoothingModes	smoothingMode
	)		const

Fills the given CSO with seedpoints according to the given list of points.

void ml::CSOMarchingSquares::findAllIsoLines	(	float	isoValue,
		bool	takeShortestPath,
		std::vector< CSOMarchingSquaresCell::vecPoint2D > &	vecPositions
	)

Finds all contours on the image with isovalue isovalue. Returns them in a vector of 2D position vectors.

void ml::CSOMarchingSquares::findIsoLine	(	int	startPosX,
		int	startPosY,
		float	isoValue,
		bool	takeShortestPath,
		CSOMarchingSquaresCell::vecPoint2D &	positions
	)

Looks for an isoline on the image.

It starts searching for a starting cell using the startPos parameters and then tracks this cell. All contour points are pushed back to the positions vector.

void ml::CSOMarchingSquares::reset ( )

Resets the state of the object.

void ml::CSOMarchingSquares::setFunction	(	CSOFunction *	implicitFunction,
		const Matrix4 &	voxelToWorldMatrix,
		int	startX,
		int	startY,
		int	imgSizeX,
		int	imgSizeY,
		int	voxelZPosition
	)		`[inline]`

Sets a 3D interpolation function, an image size and voxel size and a fixed z-offset.

NOTE that this approach supports an axial scanning of the function only at the moment; if this class should can in sagittal or coronal direction as well, some extra flag needs to be provided.

Definition at line 153 of file CSOMarchingSquares.h.