Package org.locationtech.jts.noding.snapround

Class HotPixel

java.lang.Object

org.locationtech.jts.noding.snapround.HotPixel

public class HotPixel
extends java.lang.Object

Implements a "hot pixel" as used in the Snap Rounding algorithm. A hot pixel contains the interior of the tolerance square and the boundary minus the top and right segments.

The hot pixel operations are all computed in the integer domain to avoid rounding problems.

Version:

1.7

Field Summary

Fields

Modifier and Type	Field	Description
private Coordinate[]	corner	The corners of the hot pixel, in the order: 10 23
private LineIntersector	li
private double	maxx
private double	maxy
private double	minx
private double	miny
private Coordinate	originalPt
private Coordinate	p0Scaled
private Coordinate	p1Scaled
private Coordinate	pt
private Coordinate	ptScaled
private static double	SAFE_ENV_EXPANSION_FACTOR
private Envelope	safeEnv
private double	scaleFactor

Constructor Summary

Constructors

Constructor	Description
HotPixel(Coordinate pt, double scaleFactor, LineIntersector li)	Creates a new hot pixel, using a given scale factor.

Method Summary

Modifier and Type	Method	Description
boolean	addSnappedNode(NodedSegmentString segStr, int segIndex)	Adds a new node (equal to the snap pt) to the specified segment if the segment passes through the hot pixel
private void	copyScaled(Coordinate p, Coordinate pScaled)
Coordinate	getCoordinate()	Gets the coordinate this hot pixel is based at.
Envelope	getSafeEnvelope()	Returns a "safe" envelope that is guaranteed to contain the hot pixel.
private void	initCorners(Coordinate pt)
boolean	intersects(Coordinate p0, Coordinate p1)	Tests whether the line segment (p0-p1) intersects this hot pixel.
private boolean	intersectsPixelClosure(Coordinate p0, Coordinate p1)	Test whether the given segment intersects the closure of this hot pixel.
private boolean	intersectsScaled(Coordinate p0, Coordinate p1)
private boolean	intersectsToleranceSquare(Coordinate p0, Coordinate p1)	Tests whether the segment p0-p1 intersects the hot pixel tolerance square.
private double	scale(double val)

Methods inherited from class java.lang.Object

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

Field Detail

li

private LineIntersector li

pt

private Coordinate pt

originalPt

private Coordinate originalPt

ptScaled

private Coordinate ptScaled

p0Scaled

private Coordinate p0Scaled

p1Scaled

private Coordinate p1Scaled

scaleFactor

private double scaleFactor

minx

private double minx

maxx

private double maxx

miny

private double miny

maxy

private double maxy

corner

private Coordinate[] corner

The corners of the hot pixel, in the order: 10 23

safeEnv

private Envelope safeEnv

SAFE_ENV_EXPANSION_FACTOR

private static final double SAFE_ENV_EXPANSION_FACTOR

See Also:

Constant Field Values

Constructor Detail

HotPixel

public HotPixel(Coordinate pt,
                double scaleFactor,
                LineIntersector li)

Creates a new hot pixel, using a given scale factor. The scale factor must be strictly positive (non-zero).

Parameters:

pt - the coordinate at the centre of the pixel

scaleFactor - the scaleFactor determining the pixel size. Must be > 0

li - the intersector to use for testing intersection with line segments

Method Detail

getCoordinate

public Coordinate getCoordinate()

Gets the coordinate this hot pixel is based at.

Returns:

the coordinate of the pixel

getSafeEnvelope

public Envelope getSafeEnvelope()

Returns a "safe" envelope that is guaranteed to contain the hot pixel. The envelope returned will be larger than the exact envelope of the pixel.

Returns:

an envelope which contains the hot pixel

initCorners

private void initCorners(Coordinate pt)

scale

private double scale(double val)

intersects

public boolean intersects(Coordinate p0,
                          Coordinate p1)

Tests whether the line segment (p0-p1) intersects this hot pixel.

Parameters:

p0 - the first coordinate of the line segment to test

p1 - the second coordinate of the line segment to test

Returns:

true if the line segment intersects this hot pixel

copyScaled

private void copyScaled(Coordinate p,
                        Coordinate pScaled)

intersectsScaled

private boolean intersectsScaled(Coordinate p0,
                                 Coordinate p1)

intersectsToleranceSquare

private boolean intersectsToleranceSquare(Coordinate p0,
                                          Coordinate p1)

Tests whether the segment p0-p1 intersects the hot pixel tolerance square. Because the tolerance square point set is partially open (along the top and right) the test needs to be more sophisticated than simply checking for any intersection. However, it can take advantage of the fact that the hot pixel edges do not lie on the coordinate grid. It is sufficient to check if any of the following occur:

• a proper intersection between the segment and any hot pixel edge
• an intersection between the segment and both the left and bottom hot pixel edges (which detects the case where the segment intersects the bottom left hot pixel corner)
• an intersection between a segment endpoint and the hot pixel coordinate

Parameters:

p0 -

p1 -

Returns:

intersectsPixelClosure

private boolean intersectsPixelClosure(Coordinate p0,
                                       Coordinate p1)

Test whether the given segment intersects the closure of this hot pixel. This is NOT the test used in the standard snap-rounding algorithm, which uses the partially closed tolerance square instead. This routine is provided for testing purposes only.

Parameters:

p0 - the start point of a line segment

p1 - the end point of a line segment

Returns:

true if the segment intersects the closure of the pixel's tolerance square

addSnappedNode

public boolean addSnappedNode(NodedSegmentString segStr,
                              int segIndex)

Adds a new node (equal to the snap pt) to the specified segment if the segment passes through the hot pixel

Parameters:

segStr -

segIndex -

Returns:

true if a node was added to the segment