#include <gevd_contour.h>

Public Member Functions
	gevd_contour (float min_strength, int min_length, float min_jump, float max_gap=2.236068f)
	Save parameters and create workspace for detecting contours.
	~gevd_contour ()
	Free space allocated for detecting contours.
bool	FindNetwork (gevd_bufferxy &edgels, const int njunction, const int junctionx, const int junctiony, vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices)
	Find network of linked edges and vertices, from 8-connected edge elements.
void	SubPixelAccuracy (vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices, const gevd_bufferxy &locationx, const gevd_bufferxy &locationy)
	Insert subpixel accuracy into the pixels on the edges/vertices.
void	InsertBorder (vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices)
	Insert virtual edges and vertices to enforce closure of the regions beyond the rectangular image border.
int	CheckInvariants (vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices)
	Check a few obvious invariants, and return number of errors.
Static Public Member Functions
static void	EqualizeSpacing (vcl_vector< vtol_edge_2d_sptr > &chains)
	Make the spacing of the chain pixels nearly equal by smoothing their locations with the average filter [1 0 1]/2.
static void	Translate (vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices, const float tx=0.5, const float ty=0.5)
	Translate all the pixels in the edges and vertices by (tx, ty).
static void	ClearNetwork (vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices)
	Remove and delete all elements in global lists, and set the global lists to NULL.
static void	MaskEdgels (const gevd_bufferxy &mask, gevd_bufferxy &edgels, int &njunction, int junctionx, int junctiony)
	Mask the detected edge elements and junctions with a given mask array, using AND operation, for ROI with arbitrary shapes.
static void	SetEdgelData (gevd_bufferxy &grad_mag, gevd_bufferxy &angle, vcl_vector< vtol_edge_2d_sptr > &edges)
	Set the orientation at each edgel on all digital curves to a continuous orientation value, which is consistent with C.
static int	LengthCmp (vtol_edge_2d_sptr const &dc1, vtol_edge_2d_sptr const &dc2)
	Compare function to sort the edges by their length in pixels, largest first.
static vcl_vector < vtol_edge_2d_sptr > *	CreateLookupTable (vcl_vector< vtol_edge_2d_sptr > &)
	Create a 2-way lookup table from list elements in set, using array and get_id/set_id.
static void	LookupTableInsert (vcl_vector< vtol_edge_2d_sptr > &set, vtol_edge_2d_sptr elmt)
	Insert topology object in 2-way lookup table, using Id and dynamic array.
static void	LookupTableReplace (vcl_vector< vtol_edge_2d_sptr > &set, vtol_edge_2d_sptr deleted, vtol_edge_2d_sptr inserted)
	Replace deleted by inserted in 2-way lookup table.
static void	LookupTableRemove (vcl_vector< vtol_edge_2d_sptr > &set, vtol_edge_2d_sptr elmt)
	Remove topology object from 2-way lookup table leaving an empty hole.
static void	LookupTableCompress (vcl_vector< vtol_edge_2d_sptr > &set)
	Eliminate empty holes in the lookup table.
static vcl_vector < vtol_vertex_2d_sptr > *	CreateLookupTable (vcl_vector< vtol_vertex_2d_sptr > &)
	As above for vertices.
static void	LookupTableInsert (vcl_vector< vtol_vertex_2d_sptr > &set, vtol_vertex_2d_sptr elmt)
	As above for vertices.
static void	LookupTableReplace (vcl_vector< vtol_vertex_2d_sptr > &set, vtol_vertex_2d_sptr deleted, vtol_vertex_2d_sptr inserted)
	As above for vertices.
static void	LookupTableRemove (vcl_vector< vtol_vertex_2d_sptr > &set, vtol_vertex_2d_sptr elmt)
	As above for vertices.
static void	LookupTableCompress (vcl_vector< vtol_vertex_2d_sptr > &set)
	As above for vertices.
static void	BeSilent ()
static void	BeTalkative ()
Protected Member Functions
int	FindChains (gevd_bufferxy &edgels, const int njunction, const int junctionx, const int junctiony, vcl_vector< vtol_edge_2d_sptr > &edges)
	Trace and collect pixels on thin contours, stronger pixels first, and favoring 4-connected over 8-connected.
int	FindJunctions (gevd_bufferxy &edgels, vcl_vector< vtol_edge_2d_sptr > &edges, vcl_vector< vtol_vertex_2d_sptr > &vertices)
	Find junctions from end points touching at an interior point of a chain, with detectable jump in filter response.
Protected Attributes
float	minStrength
int	minLength
float	minJump
int	maxSpiral
vbl_array_2d< vtol_edge_2d_sptr > *	edgeMap
vbl_array_2d < vtol_vertex_2d_sptr > *	vertexMap
Static Protected Attributes
static bool	talkative = true

Detailed Description

Definition at line 77 of file gevd_contour.h.

Constructor & Destructor Documentation

gevd_contour::gevd_contour	(	float	min_strength,
		int	min_length,
		float	min_jump,
		float	max_gap = `2.236068f`
	)

Save parameters and create workspace for detecting contours.

Each contour must have at least 1 pixel above min_strength, and its number of internal pixels must be above min_length. This is a heuristic hysteresis scheme that prunes weak or short isolated chains. To join a weaker contour to a stronger contour, a junction must have a change in response above min_jump on the stronger contour. This way, only strong junctions are detected.

Definition at line 73 of file gevd_contour.cxx.

gevd_contour::~gevd_contour ( )

Free space allocated for detecting contours.

Definition at line 116 of file gevd_contour.cxx.

Member Function Documentation

static void gevd_contour::BeSilent ( ) [inline, static]

Definition at line 135 of file gevd_contour.h.

static void gevd_contour::BeTalkative ( ) [inline, static]

Definition at line 136 of file gevd_contour.h.

int gevd_contour::CheckInvariants	(	vcl_vector< vtol_edge_2d_sptr > &	edges,
		vcl_vector< vtol_vertex_2d_sptr > &	vertices
	)

Check a few obvious invariants, and return number of errors.

0. Network has closure of all vertices and edges. 1. No 2 vertices touch: endpt/endpt, endpt/junction or junction/junction 2. No vertex connecting 2 edges, each vertex has 1 or >= 3 edges, except the 4 corners of image border. 3. Each edge has >= 3 internal pixels. 4. A chain can touch/join with itself or with a stronger chain. Junction is created only if the local change in filter response is greater than some noise threshold, set by the user. Junction is created only if the 2 broken up chains have lengths >= 3.

Definition at line 2014 of file gevd_contour.cxx.

void gevd_contour::ClearNetwork	(	vcl_vector< vtol_edge_2d_sptr > *&	edges,
		vcl_vector< vtol_vertex_2d_sptr > *&	vertices
	)		`[static]`

Remove and delete all elements in global lists, and set the global lists to NULL.

Remove all digital chains of edges. Edges and vertices are removed with UnProtect().

Definition at line 1749 of file gevd_contour.cxx.

vcl_vector< vtol_edge_2d_sptr > * gevd_contour::CreateLookupTable ( vcl_vector< vtol_edge_2d_sptr > & set ) [static]

Create a 2-way lookup table from list elements in set, using array and get_id/set_id.

Definition at line 1867 of file gevd_contour.cxx.

vcl_vector< vtol_vertex_2d_sptr > * gevd_contour::CreateLookupTable ( vcl_vector< vtol_vertex_2d_sptr > & set ) [static]

As above for vertices.

Definition at line 1878 of file gevd_contour.cxx.

void gevd_contour::EqualizeSpacing ( vcl_vector< vtol_edge_2d_sptr > & chains ) [static]

Make the spacing of the chain pixels nearly equal by smoothing their locations with the average filter [1 0 1]/2.

This will reduce square grid tessellation artefacts, and lead to more accurate estimation of the tangent direction, and local curvature angle, from finite differences in location. It is also useful to avoid weight artefacts in curve fitting caused by the periodic clustering of pixels along the chain. Truncating the float locations with int() will no longer map to the original pixels of the discrete chains.

Definition at line 1658 of file gevd_contour.cxx.

int gevd_contour::FindChains	(	gevd_bufferxy &	edgels,
		const int	njunction,
		const int *	junctionx,
		const int *	junctiony,
		vcl_vector< vtol_edge_2d_sptr > &	edges
	)		`[protected]`

Trace and collect pixels on thin contours, stronger pixels first, and favoring 4-connected over 8-connected.

Thinning is not used, and so will avoid errors because of square grid tessellation. A chain can not cross itself. It can only touch itself or another chain, in which case a junction will be found later. The pixels of a chain include the 2 end points. End points and junctions are created in gevd_contour::FindJunctions. Return the number of chains found. Protected.

Definition at line 277 of file gevd_contour.cxx.

int gevd_contour::FindJunctions	(	gevd_bufferxy &	edgels,
		vcl_vector< vtol_edge_2d_sptr > &	edges,
		vcl_vector< vtol_vertex_2d_sptr > &	vertices
	)		`[protected]`

Find junctions from end points touching at an interior point of a chain, with detectable jump in filter response.

Localize these junctions on the stronger contour to pixel accuracy, and break stronger chain into subchains. Also merge end points touching another end point or junction. Return the number of end points and junctions bounding all chains/cycles detected in gevd_contour::FindChains. Deletion/insertion to the network must be done completely, so that the connectivity links are updated. Protected.

Definition at line 1007 of file gevd_contour.cxx.

bool gevd_contour::FindNetwork	(	gevd_bufferxy &	edgels,
		const int	njunction,
		const int *	junctionx,
		const int *	junctiony,
		vcl_vector< vtol_edge_2d_sptr > *&	edges,
		vcl_vector< vtol_vertex_2d_sptr > *&	vertices
	)

Find network of linked edges and vertices, from 8-connected edge elements.

The contours must be less than 2 pixel wide, for example found from non maximum suppression. Isolated edgels and short segments are erased.

Definition at line 128 of file gevd_contour.cxx.

void gevd_contour::InsertBorder	(	vcl_vector< vtol_edge_2d_sptr > &	edges,
		vcl_vector< vtol_vertex_2d_sptr > &	vertices
	)

Insert virtual edges and vertices to enforce closure of the regions beyond the rectangular image border.

The location of the border is at 3 pixels away from the real image border, because of kernel radius in convolution and non maximum suppression. Virtual border of image should be inserted after gevd_contour::FindChains() and gevd_contour::FindJunctions().

JLM - February 1999 Modified this routine extensively to move the border to the actual image ROI bounds. Chain endpoints are extended to intersect with the border. These changes were made to support region segmentation from edgels.

Definition at line 1318 of file gevd_contour.cxx.

int gevd_contour::LengthCmp	(	vtol_edge_2d_sptr const &	dc1,
		vtol_edge_2d_sptr const &	dc2
	)		`[static]`

Compare function to sort the edges by their length in pixels, largest first.

Definition at line 1857 of file gevd_contour.cxx.

void gevd_contour::LookupTableCompress ( vcl_vector< vtol_edge_2d_sptr > & set ) [static]

Eliminate empty holes in the lookup table.

Definition at line 1957 of file gevd_contour.cxx.

void gevd_contour::LookupTableCompress ( vcl_vector< vtol_vertex_2d_sptr > & set ) [static]

As above for vertices.

Definition at line 1981 of file gevd_contour.cxx.

void gevd_contour::LookupTableInsert	(	vcl_vector< vtol_edge_2d_sptr > &	set,
		vtol_edge_2d_sptr	elmt
	)		`[static]`

Insert topology object in 2-way lookup table, using Id and dynamic array.

Protect it in the network.

Definition at line 1892 of file gevd_contour.cxx.

void gevd_contour::LookupTableInsert	(	vcl_vector< vtol_vertex_2d_sptr > &	set,
		vtol_vertex_2d_sptr	elmt
	)		`[static]`

As above for vertices.

Definition at line 1902 of file gevd_contour.cxx.

void gevd_contour::LookupTableRemove	(	vcl_vector< vtol_edge_2d_sptr > &	set,
		vtol_edge_2d_sptr	elmt
	)		`[static]`

Remove topology object from 2-way lookup table leaving an empty hole.

Also remove object from the network.

Definition at line 1939 of file gevd_contour.cxx.

void gevd_contour::LookupTableRemove	(	vcl_vector< vtol_vertex_2d_sptr > &	set,
		vtol_vertex_2d_sptr	elmt
	)		`[static]`

As above for vertices.

Definition at line 1948 of file gevd_contour.cxx.

void gevd_contour::LookupTableReplace	(	vcl_vector< vtol_edge_2d_sptr > &	set,
		vtol_edge_2d_sptr	deleted,
		vtol_edge_2d_sptr	inserted
	)		`[static]`

Replace deleted by inserted in 2-way lookup table.

Also remove object from the network.

Definition at line 1913 of file gevd_contour.cxx.

void gevd_contour::LookupTableReplace	(	vcl_vector< vtol_vertex_2d_sptr > &	set,
		vtol_vertex_2d_sptr	deleted,
		vtol_vertex_2d_sptr	inserted
	)		`[static]`

As above for vertices.

Definition at line 1927 of file gevd_contour.cxx.

void gevd_contour::MaskEdgels	(	const gevd_bufferxy &	mask,
		gevd_bufferxy &	edgels,
		int &	njunction,
		int *	junctionx,
		int *	junctiony
	)		`[static]`

Mask the detected edge elements and junctions with a given mask array, using AND operation, for ROI with arbitrary shapes.

Definition at line 1781 of file gevd_contour.cxx.

void gevd_contour::SetEdgelData	(	gevd_bufferxy &	grad_mag,
		gevd_bufferxy &	angle,
		vcl_vector< vtol_edge_2d_sptr > &	edges
	)		`[static]`

Set the orientation at each edgel on all digital curves to a continuous orientation value, which is consistent with C.

Rothwell's EdgeDetector. That is theta = (180/M_PI)*atan2(dI/dy, dI/dx)

Definition at line 1809 of file gevd_contour.cxx.

void gevd_contour::SubPixelAccuracy	(	vcl_vector< vtol_edge_2d_sptr > &	edges,
		vcl_vector< vtol_vertex_2d_sptr > &	vertices,
		const gevd_bufferxy &	locationx,
		const gevd_bufferxy &	locationy
	)

Insert subpixel accuracy into the pixels on the edges/vertices.

Truncating float locations with int(xy) should map to the original pixel locations. No interpolation is done at junctions of 3 or more contours, so a junction can have location error up to 1-2 pixel, tangential to the strong contour.

Definition at line 1232 of file gevd_contour.cxx.

void gevd_contour::Translate	(	vcl_vector< vtol_edge_2d_sptr > &	edges,
		vcl_vector< vtol_vertex_2d_sptr > &	vertices,
		const float	tx = `0.5`,
		const float	ty = `0.5`
	)		`[static]`

Translate all the pixels in the edges and vertices by (tx, ty).

If the image is extracted from an ROI, a translation of (roi->GetOrigX(), roi->GetOrigY()) must be done to have coordinates in the reference frame of the original image. Add 0.5 if you want to display location at center of pixel instead of upper-left corner.

Definition at line 1709 of file gevd_contour.cxx.