Class to manipulate a line segment The class is parametrized in terms the position of the centre, its length and orientation. This is thus compatible with the output of the Berkeley edge detector. We store also the start point, the end point and the line parameters describing this line segment (for more details on how the line parameters work, please see the class line). This is redundant information, but it is convenient to have all these parameters precomputed and at hand. More...

#include <gr_line_segment.h>

Inheritance diagram for kjb::Line_segment:

Public Member Functions
	Line_segment ()
	Constructor without initializations. More...

	Line_segment (double icentre_x, double icentre_y, double iorientation, double ilength)
	Constructs a new Line_segment from centre, orientation, length. More...

	Line_segment (const Vector &start, const Vector &end)
	Constructs a new Line_segment from a starting and ending point. More...

	Line_segment (std::istream &in)
	Constructs this line segment by reading from an input stream. More...

	Line_segment (const Line_segment &ls)
	Copy constructor. More...

Line_segment &	operator= (const Line_segment &ls)
	Assignment operator. More...

bool	operator== (const Line_segment &ls) const

bool	operator< (const Line_segment &ls) const

void	init_from_slope_and_intercept (double x_start, double x_end, double islope, double iintercept)
	Initialize from x_start, x_end, slope, y_axis intercept. More...

void	init_vertical_segment (double y_start, double y_end, double x)
	Initialize a vertical Line_segment from y_start, y_end, x coord. More...

void	init_from_end_points (double x_1, double y_1, double x_2, double y_2)
	Initialize a new Line_segment from position of its end points. More...

void	init_from_centre_and_orientation (double icentre_x, double icentre_y, double iorientation, double ilength)

double	get_centre_x () const
	Returns the x-coordinate of the mid-point. More...

double	get_centre_y () const
	Returns the y-coordinate of the mid-point. More...

bool	point_outside_segment (const Vector &point) const
	Check whether point is inside the ending points of this segment Note point is collinear with this line segment. More...

const kjb::Vector &	get_centre () const
	Returns the mid-point. More...

double	get_start_x () const
	Returns the x-coordinate of the leftmost point of the segment. More...

double	get_start_y () const
	Returns the y-coordinate of the leftmost point of the segment. More...

const kjb::Vector &	get_start () const
	Returns the leftmost point of the segment. More...

double	get_end_x () const
	Returns the x-coordinate of the rightmost point of the segment. More...

double	get_end_y () const
	Returns the y-coordinate of the rightmost point of the segment. More...

const kjb::Vector &	get_end () const
	Returns the rightmost point of the segment. More...

double	get_slope () const
	Returns the slope of the line segment. More...

double	get_y_intercept () const
	Returns the y-intercept of the line segment. More...

double	get_x_intercept () const
	Returns the x-intercept of the line segment. More...

const Vector &	get_line_params () const

const Line &	get_line () const

double	get_orientation () const
	Returns the orientation. More...

double	get_length () const
	Returns the length. More...

void	read (std::istream &in)
	Reads this Line segment from an input stream. More...

void	write (std::ostream &out) const
	Writes this Line segment to an output stream. More...

void	draw (kjb::Image &img, double ir, double ig, double ib, double width=1.0) const
	Draws this line segment. More...

void	randomly_color (kjb::Image &img, double width=1.0) const
	Randomly colors this line segment on an image. More...

bool	get_intersection (const Line_segment &line, kjb::Vector &point) const
	Finds the intersection point of the this line_segment and the input Line_segment line. Return false if these two lines are parallel and therefore do not intersect. More...

double	get_distance_from_point (const kjb::Vector &point) const
	Returns distance between this line segment and the input point. More...

double	get_angle_between_line (const Line_segment &line) const
	Returns the angle between this line segment and the input line. More...

double	find_t (const kjb::Vector &point) const

double	get_distance_from_point (const kjb::Vector &point, double *perp_dist) const
	Returns distance between this line segment and the input point. More...

double	get_dx () const
	Returns the dx of this segment. More...

double	get_dy () const
	Returns the dy of this segment. More...

bool	is_horizontal () const
	Function object of testing whehter a line is horizontal. More...

bool	is_vertical () const
	Function object of testing whehter a line is horizontal. More...

void	get_direction (kjb::Vector &idirection) const
	Returns a vector representing the normalized direction of this line_segment. More...

bool	is_line_segment_consistent ()

bool	is_collinear (const Line_segment &ls, double collinear_threshold) const

Public Member Functions inherited from kjb::Readable
virtual	~Readable ()
	Deletes this Readable. More...

virtual void	read (const char *fname)
	Reads this Readable from a file. More...

Public Member Functions inherited from kjb::Writeable
virtual	~Writeable ()
	Deletes this Writeable. More...

virtual void	write (const char *fname) const
	Writes this Writeable to a file. More...

Static Public Member Functions
static std::pair< Vector, Vector >	project_line_segment_onto_line (const Line_segment &segment, const Line &iline)
	Project a line segment onto a line. More...

static bool	project_line_segment_onto_line_segment (const Line_segment &segment_project, const Line_segment &segment_target, std::pair< Vector, Vector > &projected_points, double &length_inside, double &length_outside)
	Project a line segment onto a line segment. More...

static bool	less_than (const Vector &point1, const Vector &point2)
	Returns true if point1.x < point2.x \|\| (point1.x == point2.x && point1.y < point2.y. More...

static bool	collision_detection (double start_1, double end_1, double start_2, double end_2, int &direction, double &delta)

static bool	collision_detection_with_direction (double start_1, double end_1, double start_2, double end_2, int &direction, double &delta, int idirection)

static double	get_overlap (double start_1, double end_1, double start_2, double end_2)

Static Public Member Functions inherited from kjb::Readable
static const char *	read_field_value (std::istream &in, const char field_name, char field_buf, size_t buf_len, char separator=':')
	Reads a line off in into a buffer and returns a pointer to the field value in the buffer. More...

static const char *	read_field_value (std::istream &in, const char *field_name, char separator=':')
	Reads a line off in into an internal buffer and returns a pointer to the field value in the buffer. More...

Protected Member Functions
void	compute_extrema ()
	Computes the extrema of this line segments from centre, orientation, and length. This information is redundant, but it can be very useful to have them pre-computed. More...

void	compute_line_parameters ()

Protected Attributes
kjb::Vector	centre
	X coordinate of the centre of this line segment. More...

double	orientation
	Orientation of this line segment, defined as the angle between the x axis and the segment, positive angle meaning counter clockwise. Ranges between 0 and 180 degrees. Stored in radian. More...

double	length
	length of the line segment More...

kjb::Vector	start_point

kjb::Vector	end_point

Line	line

Static Protected Attributes
static Matrix	_line_segment_rotation

Friends
std::ostream &	operator<< (std::ostream &, const Line_segment &)

Detailed Description

Class to manipulate a line segment The class is parametrized in terms the position of the centre, its length and orientation. This is thus compatible with the output of the Berkeley edge detector. We store also the start point, the end point and the line parameters describing this line segment (for more details on how the line parameters work, please see the class line). This is redundant information, but it is convenient to have all these parameters precomputed and at hand.

Constructor & Destructor Documentation

kjb::Line_segment::Line_segment ( )

inline

Constructor without initializations.

kjb::Line_segment::Line_segment	(	double	icentre_x,
		double	icentre_y,
		double	iorientation,
		double	ilength
	)

Constructs a new Line_segment from centre, orientation, length.

Parameters

icentre_x	the x coordinate of the centre
icentre_y	the y coordinate of the centre
iorientation	the orientation of the segment, defined as the angle between the x axis and the segment, positive meaning counter clockwise rotation. The value will be converted to the range [0-180] degrees
ilength	the length of the segment

kjb::Line_segment::Line_segment	(	const Vector &	start,
		const Vector &	end
	)

Constructs a new Line_segment from a starting and ending point.

kjb::Line_segment::Line_segment ( std::istream & in )

Constructs this line segment by reading from an input stream.

kjb::Line_segment::Line_segment ( const Line_segment & ls )

Copy constructor.

Parameters

ls	the line segment to copy into this one

Member Function Documentation

bool kjb::Line_segment::collision_detection	(	double	start_1,
		double	end_1,
		double	start_2,
		double	end_2,
		int &	direction,
		double &	delta
	)

static

bool kjb::Line_segment::collision_detection_with_direction	(	double	start_1,
		double	end_1,
		double	start_2,
		double	end_2,
		int &	direction,
		double &	delta,
		int	idirection
	)

static

void kjb::Line_segment::compute_extrema ( )

protected

Computes the extrema of this line segments from centre, orientation, and length. This information is redundant, but it can be very useful to have them pre-computed.

Computes the extrema from the line segment parameters. It initializes the extrema so that the segment is aligned with the x axis , centred int the origin and has the correct length. It then rotates it so that it has the correct orientation, and finally translates it to the reight position

void kjb::Line_segment::compute_line_parameters ( )

protected

Computes the slope and the y-axis intercept of this segment This information is redundant, but it can be very useful to have it pre-computed.

Computes the slope and the y-axis intercept of this segment

void kjb::Line_segment::draw	(	kjb::Image &	img,
		double	ir,
		double	ig,
		double	ib,
		double	width = `1.0`
	)		const

Draws this line segment.

Draws the line segment on an image

Parameters

img	the image
ir	the red channel
ig	the green channel
ib	the blue channel
width	the width of the segment to be drawn (in pixel)

double kjb::Line_segment::find_t ( const kjb::Vector & point ) const

If we interpret the end points p1 and p2 of this line segment as the two points defining the parametric equation of a line, given an input point p, this function returns the parameter t such that: p = p2 + t (p2 -p1) Notice that this works even if p is not on the line, its projection on it will be considered.

Parameters

point The point to compute t for

double kjb::Line_segment::get_angle_between_line ( const Line_segment & line_segment ) const

Returns the angle between this line segment and the input line.

Calculate the angle between this line segment and the input line_segment.

Returns: the calculated angle

const kjb::Vector& kjb::Line_segment::get_centre ( ) const

inline

Returns the mid-point.

double kjb::Line_segment::get_centre_x ( ) const

inline

Returns the x-coordinate of the mid-point.

double kjb::Line_segment::get_centre_y ( ) const

inline

Returns the y-coordinate of the mid-point.

void kjb::Line_segment::get_direction ( kjb::Vector & idirection ) const

Returns a vector representing the normalized direction of this line_segment.

Returns a vector representing the normalized direction of this line_segment

Parameters

idirection This will contain the line segment direction

double kjb::Line_segment::get_distance_from_point ( const kjb::Vector & point ) const

Returns distance between this line segment and the input point.

Returns the distance between this line segment and the input point. There are two case: 1) The perpendicular projection of the point onto the line the segment lies on falls onto the line segment. In this case we return this perpendicular distance 2) Otherwise, we return the smallest distance between one of the segment end points and the input point

Parameters

point the input point

double kjb::Line_segment::get_distance_from_point	(	const kjb::Vector &	point,
		double *	perp_dist
	)		const

Returns distance between this line segment and the input point.

Returns the distance between this line segment and the input point. There are two case: 1) The perpendicular projection of the point onto the line the segment lies on falls onto the line segment. In this case we return this perpendicular distance 2) Otherwise, we return the smallest distance between one of the segment end points and the input point

Parameters

point the input point

Returns: the perpendicular distance between the line the segment lies on and the point. If we are in case (1) these two distances are the same

double kjb::Line_segment::get_dx ( ) const

inline

Returns the dx of this segment.

double kjb::Line_segment::get_dy ( ) const

inline

Returns the dy of this segment.

const kjb::Vector& kjb::Line_segment::get_end ( ) const

inline

Returns the rightmost point of the segment.

double kjb::Line_segment::get_end_x ( ) const

inline

Returns the x-coordinate of the rightmost point of the segment.

double kjb::Line_segment::get_end_y ( ) const

inline

Returns the y-coordinate of the rightmost point of the segment.

bool kjb::Line_segment::get_intersection	(	const Line_segment &	_line,
		kjb::Vector &	point_p
	)		const

Finds the intersection point of the this line_segment and the input Line_segment line. Return false if these two lines are parallel and therefore do not intersect.

Parameters

line	input Line_segment
point	the intersection point

Finds the intersection between the line this line_segment lies ont and the line the input line_segment lies on. Return false if these two lines are parallel and therefore do not intersect

Parameters

_line	The input line_segment
point_p	Will contain the intersection point

Returns: false if the lines do not intesect

double kjb::Line_segment::get_length ( ) const

inline

Returns the length.

const Line& kjb::Line_segment::get_line ( ) const

inline

const Vector& kjb::Line_segment::get_line_params ( ) const

inline

double kjb::Line_segment::get_orientation ( ) const

inline

Returns the orientation.

double kjb::Line_segment::get_overlap	(	double	start_1,
		double	end_1,
		double	start_2,
		double	end_2
	)

static

double kjb::Line_segment::get_slope ( ) const

inline

Returns the slope of the line segment.

If the segment is vertical, the slope tends to infinity.

const kjb::Vector& kjb::Line_segment::get_start ( ) const

inline

Returns the leftmost point of the segment.

double kjb::Line_segment::get_start_x ( ) const

inline

Returns the x-coordinate of the leftmost point of the segment.

double kjb::Line_segment::get_start_y ( ) const

inline

Returns the y-coordinate of the leftmost point of the segment.

double kjb::Line_segment::get_x_intercept ( ) const

inline

Returns the x-intercept of the line segment.

If the segment is horizontal there is not such interception.

double kjb::Line_segment::get_y_intercept ( ) const

inline

Returns the y-intercept of the line segment.

If the segment is vertical there is not such interception.

void kjb::Line_segment::init_from_centre_and_orientation	(	double	icentre_x,
		double	icentre_y,
		double	iorientation,
		double	ilength
	)

Parameters

icentre_x	the x coordinate of the centre
icentre_y	the y coordinate of the centre
iorientation	the orientation of the segment, defined as the angle between the x axis and the segment, positive meaning counter clockwise rotation. The value will be converted to the range [0-180] degrees
ilength	the length of the segment

void kjb::Line_segment::init_from_end_points	(	double	x_1,
		double	y_1,
		double	x_2,
		double	y_2
	)

Initialize a new Line_segment from position of its end points.

Parameters

x_1	the x coordinate of the first end point
y_1	the y coordinate of the first end point
x_2	the x coordinate of the second end point
y_2	the y coordinate of the second end point

void kjb::Line_segment::init_from_slope_and_intercept	(	double	x_start,
		double	x_end,
		double	islope,
		double	iintercept
	)

Initialize from x_start, x_end, slope, y_axis intercept.

Notice that a vertical segment cannot be initialized with this function.

Parameters

x_start	the x coordinate of the first endpoint
x_end	the x coordinate of the second endpoint
im	slope of the line segment
ib	y intercept

void kjb::Line_segment::init_vertical_segment	(	double	y_start,
		double	y_end,
		double	x
	)

Initialize a vertical Line_segment from y_start, y_end, x coord.

This function inits this line segment as a vertical segment defined by the x location and a start and end point along the y direction.

Parameters

y_start	the y coordinate of the bottom of this segment
y_end	the y coordinate of the first endpoint
x	the x coordinate of the second endpoint

bool kjb::Line_segment::is_collinear	(	const Line_segment &	ls,
		double	collinear_threshold
	)		const

bool kjb::Line_segment::is_horizontal ( ) const

inline

Function object of testing whehter a line is horizontal.

bool kjb::Line_segment::is_line_segment_consistent ( )

For debug purposes, checks this line segment is consistent

For debugging purposes. It checks that the line segment parameters are consistent

bool kjb::Line_segment::is_vertical ( ) const

inline

Function object of testing whehter a line is horizontal.

bool kjb::Line_segment::less_than	(	const Vector &	point1,
		const Vector &	point2
	)

static

Returns true if point1.x < point2.x || (point1.x == point2.x && point1.y < point2.y.

bool kjb::Line_segment::operator< ( const Line_segment & ls ) const

inline

Line_segment & kjb::Line_segment::operator= ( const Line_segment & ls )

Assignment operator.

Parameters

ls	the line segment to assign to this one

bool kjb::Line_segment::operator== ( const Line_segment & ls ) const

Parameters

ls	the line segment to compare to this one

bool kjb::Line_segment::point_outside_segment ( const Vector & point ) const

Check whether point is inside the ending points of this segment Note point is collinear with this line segment.

std::pair< Vector, Vector > kjb::Line_segment::project_line_segment_onto_line	(	const Line_segment &	segment,
		const Line &	iline
	)

static

Project a line segment onto a line.

Returns: The projected two ending points of the line segment; std::pair<Vector, Vector> The projected two ending points of the line segment

(not fully tested)

bool kjb::Line_segment::project_line_segment_onto_line_segment	(	const Line_segment &	segment_project,
		const Line_segment &	segment_target,
		std::pair< Vector, Vector > &	projected_points,
		double &	length_inside,
		double &	length_outside
	)

static

Project a line segment onto a line segment.

Parameters

segment_project	The line segment that is being projected
segment_target	The line segment that is being projected to
projected_points	The projected two ending points of the line segment.

Returns: True If both projected_points are inside the ending points of segment_target, False If one or both the projected_points are outside the ending points the segment_target.

Parameters

segment_project	The line segment that is being projected
segment_target	The line segment that is being projected to
projected_points	The projected two ending points of the line segment

Returns: True If both projected_points are inside the ending points of segment_target, False If one or both the projected_points are outside the ending points the segment_target

void kjb::Line_segment::randomly_color	(	kjb::Image &	img,
		double	width = `1.0`
	)		const

Randomly colors this line segment on an image.

Draws the line segment using a random color

Parameters

img	the image
width	the width of the segment to be drawn (in pixel)

void kjb::Line_segment::read ( std::istream & in )

virtual

Reads this Line segment from an input stream.

Reads this Line_segment from an input stream.

Implements kjb::Readable.

Reimplemented in kjb::Model_edge.

void kjb::Line_segment::write ( std::ostream & out ) const

virtual

Writes this Line segment to an output stream.

Writes this Line_segment to an output stream.

Implements kjb::Writeable.

Reimplemented in kjb::Model_edge.

Friends And Related Function Documentation

std::ostream& operator<<	(	std::ostream &	,
		const Line_segment &
	)

friend

Member Data Documentation

Matrix kjb::Line_segment::_line_segment_rotation

staticprotected

kjb::Vector kjb::Line_segment::centre

protected

X coordinate of the centre of this line segment.

kjb::Vector kjb::Line_segment::end_point

protected

double kjb::Line_segment::length

protected

length of the line segment

Line kjb::Line_segment::line

protected

Line parameters. The following parameters are redundant, but it can be helpful to have them pre-computed.

double kjb::Line_segment::orientation

protected

Orientation of this line segment, defined as the angle between the x axis and the segment, positive angle meaning counter clockwise. Ranges between 0 and 180 degrees. Stored in radian.

kjb::Vector kjb::Line_segment::start_point

protected

Start and end point of the line segment. The following fields are redundant, but it can be helpful to have them pre-computed.

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

/work/kobus/src/lib/gr_cpp/gr_line_segment.h
/work/kobus/src/lib/gr_cpp/gr_line_segment.cpp

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Static Protected Attributes

Friends

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Friends And Related Function Documentation

Member Data Documentation