AprilTags::Quad Class Reference

Represents four segments that form a loop, and might be a tag. More...

#include <Quad.h>

Detailed Description

Represents four segments that form a loop, and might be a tag.

Definition at line 22 of file Quad.h.

Public Member Functions
	Quad (const std::vector< std::pair< float, float > > &p, const std::pair< float, float > &opticalCenter)
	Constructor.
std::pair< float, float >	interpolate (float x, float y)
	Interpolate given that the lower left corner of the lower left cell is at (-1,-1) and the upper right corner of the upper right cell is at (1,1).
std::pair< float, float >	interpolate01 (float x, float y)
	Same as interpolate, except that the coordinates are interpreted between 0 and 1, instead of -1 and 1.
Static Public Member Functions
static void	search (const FloatImage &fImage, std::vector< Segment * > &path, Segment &parent, int depth, std::vector< Quad > &quads)
	Searches through a vector of Segments to form Quads.
Public Attributes
std::vector< std::pair< float, float > >	quadPoints
	Points for the quad (in pixel coordinates), in counter clockwise order. These points are the intersections of segments.
std::vector< Segment * >	segments
	Segments composing this quad.
float	observedPerimeter
	Total length (in pixels) of the actual perimeter observed for the quad.
Homography33	homography
	Given that the whole quad spans from (0,0) to (1,1) in "quad space", compute the pixel coordinates for a given point within that quad.
Static Public Attributes
static const int	minimumEdgeLength = 6
	Minimum size of a tag (in pixels) as measured along edges and diagonals.
static float const	maxQuadAspectRatio = 32
	Early pruning of quads with insane ratios.
Private Attributes
fmat::Column< 2, float >	p0
fmat::Column< 2, float >	p3
fmat::Column< 2, float >	p01
fmat::Column< 2, float >	p32

Constructor & Destructor Documentation

AprilTags::Quad::Quad	(	const std::vector< std::pair< float, float > > &	p,
		const std::pair< float, float > &	opticalCenter
	)

Constructor.

(x,y) are the optical center of the camera, which is needed to correctly compute the homography.

Definition at line 11 of file Quad.cc.

Member Function Documentation

std::pair< float, float > AprilTags::Quad::interpolate	(	float	x,
		float	y
	)

Interpolate given that the lower left corner of the lower left cell is at (-1,-1) and the upper right corner of the upper right cell is at (1,1).

Definition at line 36 of file Quad.cc.

Referenced by interpolate01().

std::pair<float,float> AprilTags::Quad::interpolate01	(	float	x,
		float	y
	)

Same as interpolate, except that the coordinates are interpreted between 0 and 1, instead of -1 and 1.

Definition at line 36 of file Quad.h.

Referenced by AprilTags::TagDetector::extractTags().

void AprilTags::Quad::search	(	const FloatImage &	fImage,
		std::vector< Segment * > &	path,
		Segment &	parent,
		int	depth,
		std::vector< Quad > &	quads
	)			`[static]`

Searches through a vector of Segments to form Quads.

Definition at line 48 of file Quad.cc.

Referenced by AprilTags::TagDetector::extractTags().

Member Data Documentation

Homography33 AprilTags::Quad::homography

Given that the whole quad spans from (0,0) to (1,1) in "quad space", compute the pixel coordinates for a given point within that quad.

Note that for most of the Quad's existence, we will not know the correct orientation of the tag.

Definition at line 53 of file Quad.h.

Referenced by AprilTags::TagDetector::extractTags(), interpolate(), and Quad().

const float AprilTags::Quad::maxQuadAspectRatio = 32 [static]

Early pruning of quads with insane ratios.

Definition at line 25 of file Quad.h.

Referenced by search().

const int AprilTags::Quad::minimumEdgeLength = 6 [static]

Minimum size of a tag (in pixels) as measured along edges and diagonals.

Definition at line 24 of file Quad.h.

Referenced by search().

float AprilTags::Quad::observedPerimeter

Total length (in pixels) of the actual perimeter observed for the quad.

This is in contrast to the geometric perimeter, some of which may not have been directly observed but rather inferred by intersecting segments. Quads with more observed perimeter are preferred over others.

Definition at line 49 of file Quad.h.

Referenced by AprilTags::TagDetector::extractTags().

fmat::Column<2,float> AprilTags::Quad::p0 [private]

Definition at line 66 of file Quad.h.

Referenced by interpolate(), and Quad().

fmat::Column<2,float> AprilTags::Quad::p01 [private]

Definition at line 66 of file Quad.h.

Referenced by interpolate(), and Quad().

fmat::Column<2,float> AprilTags::Quad::p3 [private]

Definition at line 66 of file Quad.h.

Referenced by interpolate(), and Quad().

fmat::Column<2,float> AprilTags::Quad::p32 [private]