Module org.jhotdraw8.geom

Package org.jhotdraw8.geom.intersect

Class IntersectLinePoint

java.lang.Object

org.jhotdraw8.geom.intersect.IntersectLinePoint

public class IntersectLinePoint
extends Object

Method Summary

Modifier and Type	Method	Description
static double	argumentOnLine(double x1, double y1, double x2, double y2, double px, double py)	Given a point p on a line, computes the value of the argument 't'.
static @NonNull IntersectionResult	intersectLinePoint(double x0, double y0, double x1, double y1, double cx, double cy, double r)	Computes the intersection between a line and a point with tolerance radius r.
static @NonNull IntersectionResultEx	intersectLinePointEx(double x0, double y0, double x1, double y1, double cx, double cy, double r)
static boolean	lineContainsPoint(double x1, double y1, double x2, double y2, double px, double py)
static boolean	lineContainsPoint(double x1, double y1, double x2, double y2, double px, double py, double tolerance)	Tests if a point is inside a line segment.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

intersectLinePoint

public static @NonNull IntersectionResult intersectLinePoint(double x0,
 double y0,
 double x1,
 double y1,
 double cx,
 double cy,
 double r)

Computes the intersection between a line and a point with tolerance radius r.

The returned intersection contain the parameters 't1' of the line in range [0,1].

The intersection will have one of the following status:

• IntersectionStatus.INTERSECTION
• IntersectionStatus.NO_INTERSECTION

This method solves the last equation shown in the list below.

1. p0 + (p1 - p0) · t1 , 0 ≤ t1 ≤ 1
   : line equation in vector form
2. x0 + (x1 - x0) · t1, y0 + (y1 - y0) · t1
   : line equation in matrix form
3. x0 + Δx · t1, y0 + Δy · t1
   : partially compacted coefficients
4. fx, fy
   : compacted coefficients in matrix form
5. (fx - cx)² + (fy - cy)² = 0
   : distance to point equation with fx, fy coefficients inserted
6. Δx²·Δy²·t1²
   + 2·(Δx·(x0 - cx)+Δy·(y0 - cy))·t1
   - 2·(x0·cx + y0·cy) + cx² + cy² + x0² + y0² = 0
   : fx, fy coefficients expanded and equation reordered
7. a·t1² + b·t1 + c = 0, 0 ≤ t1 ≤ 1
   : final quadratic polynomial
8. 2·a·t1 + b = 0, 0 ≤ t1 ≤ 1
   : derivative

Parameters:

x0 - point 0 of the line

y0 - point 0 of the line

x1 - point 1 of the line

y1 - point 1 of the line

cx - the center of the point p.x

cy - the center of the point p.y

r - the tolerance radius

Returns:

computed intersection

intersectLinePointEx

public static @NonNull IntersectionResultEx intersectLinePointEx(double x0,
 double y0,
 double x1,
 double y1,
 double cx,
 double cy,
 double r)

lineContainsPoint

public static boolean lineContainsPoint(double x1,
 double y1,
 double x2,
 double y2,
 double px,
 double py)

lineContainsPoint

public static boolean lineContainsPoint(double x1,
 double y1,
 double x2,
 double y2,
 double px,
 double py,
 double tolerance)

Tests if a point is inside a line segment.

Parameters:

x1 - the x coordinate of point 1 on the line

y1 - the y coordinate of point 1 on the line

x2 - the x coordinate of point 2 on the line

y2 - the y coordinate of point 2 on the line

px - the x coordinate of the point

py - the y coordinate of the point

tolerance - the maximal distance that the point may stray from the line

Returns:

true if the line contains the point within the given tolerance

argumentOnLine

public static double argumentOnLine(double x1,
 double y1,
 double x2,
 double y2,
 double px,
 double py)

Given a point p on a line, computes the value of the argument 't'.

If the point p is not on the line it is projected perpendicularly on the line. In this case 't' may be outside of the range [0,1].

Parameters:

x1 - start of line

y1 - start of line

x2 - end of line

y2 - end of line

px - point

py - point

Returns:

argument 't' at point px,py on the line.