Class pinside (o2scl)

O2scl : Class List

class pinside

Test line intersection and point inside polygon.

This is a fast and dirty implementation of the point inside polygon test from Jerome L. Lewis, SIGSCE Bulletin, 34 (2002) 81.

Note that an error in that article (“count-” should have been “count–”) has been corrected here.

Idea for Future:

The inside() functions actually copy the points twice. This can be made more efficient.

Public Types

typedef boost::numeric::ublas::vector<double> ubvector

Public Functions

inline int intersect(double x1, double y1, double x2, double y2, double x3, double y3, double x4, double y4)

Determine if two line segments intersect.

The function returns 1 if the line segment determined by the endpoints \( (x_1,y_1) \) and \( (x_2,y_2) \) and the line segment determined by the endpoints \( (x_3,y_3) \) and \( (x_4,y_4) \) intersect, and 0 otherwise.

int inside(double x, double y, const ubvector &xa, const ubvector &ya)

Determine if point (x,y) is inside a polygon.

This returns 1 if the point (x,y) is inside the polygon defined by xa and ya, and 0 otherwise.

Note that if the point (x,y) is exactly on the polygon, then the result of this function is not well-defined and it will return either 0 or 1.

template<class vec_t>
inline int inside(double x, double y, size_t n, const vec_t &xa, const vec_t &ya)

Determine if point (x,y) is inside a polygon.

This returns 1 if the point (x,y) is inside the polygon defined by xa and ya, and 0 otherwise.

The parameter n should be the number of polygon points specified in vectors xa and ya.

Note that if the point (x,y) is exactly on the polygon, then the result of this function is not well-defined and it will return either 0 or 1.

int test(test_mgr &t)

Perform some simple testing.

Protected Functions

int intersect(line P, line Q)

Test if line segments P and Q intersect.

int inside(point t, point p[], int N)

Test if point t is inside polygon p of size N.

struct line

Internal line definition for pinside.

Public Members

point p1

point p2

struct point

Internal point definition for pinside.

Public Members

double x

double y