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The Polygon.java Java example source code
/*
* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.awt;
import java.awt.geom.AffineTransform;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import sun.awt.geom.Crossings;
import java.util.Arrays;
/**
* The <code>Polygon class encapsulates a description of a
* closed, two-dimensional region within a coordinate space. This
* region is bounded by an arbitrary number of line segments, each of
* which is one side of the polygon. Internally, a polygon
* comprises of a list of {@code (x,y)}
* coordinate pairs, where each pair defines a <i>vertex of the
* polygon, and two successive pairs are the endpoints of a
* line that is a side of the polygon. The first and final
* pairs of {@code (x,y)} points are joined by a line segment
* that closes the polygon. This <code>Polygon is defined with
* an even-odd winding rule. See
* {@link java.awt.geom.PathIterator#WIND_EVEN_ODD WIND_EVEN_ODD}
* for a definition of the even-odd winding rule.
* This class's hit-testing methods, which include the
* <code>contains, intersects and inside
* methods, use the <i>insideness definition described in the
* {@link Shape} class comments.
*
* @author Sami Shaio
* @see Shape
* @author Herb Jellinek
* @since 1.0
*/
public class Polygon implements Shape, java.io.Serializable {
/**
* The total number of points. The value of <code>npoints
* represents the number of valid points in this <code>Polygon
* and might be less than the number of elements in
* {@link #xpoints xpoints} or {@link #ypoints ypoints}.
* This value can be NULL.
*
* @serial
* @see #addPoint(int, int)
* @since 1.0
*/
public int npoints;
/**
* The array of X coordinates. The number of elements in
* this array might be more than the number of X coordinates
* in this <code>Polygon. The extra elements allow new points
* to be added to this <code>Polygon without re-creating this
* array. The value of {@link #npoints npoints} is equal to the
* number of valid points in this <code>Polygon.
*
* @serial
* @see #addPoint(int, int)
* @since 1.0
*/
public int xpoints[];
/**
* The array of Y coordinates. The number of elements in
* this array might be more than the number of Y coordinates
* in this <code>Polygon. The extra elements allow new points
* to be added to this <code>Polygon without re-creating this
* array. The value of <code>npoints is equal to the
* number of valid points in this <code>Polygon.
*
* @serial
* @see #addPoint(int, int)
* @since 1.0
*/
public int ypoints[];
/**
* The bounds of this {@code Polygon}.
* This value can be null.
*
* @serial
* @see #getBoundingBox()
* @see #getBounds()
* @since 1.0
*/
protected Rectangle bounds;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = -6460061437900069969L;
/*
* Default length for xpoints and ypoints.
*/
private static final int MIN_LENGTH = 4;
/**
* Creates an empty polygon.
* @since 1.0
*/
public Polygon() {
xpoints = new int[MIN_LENGTH];
ypoints = new int[MIN_LENGTH];
}
/**
* Constructs and initializes a <code>Polygon from the specified
* parameters.
* @param xpoints an array of X coordinates
* @param ypoints an array of Y coordinates
* @param npoints the total number of points in the
* <code>Polygon
* @exception NegativeArraySizeException if the value of
* <code>npoints is negative.
* @exception IndexOutOfBoundsException if <code>npoints is
* greater than the length of <code>xpoints
* or the length of <code>ypoints.
* @exception NullPointerException if <code>xpoints or
* <code>ypoints is null.
* @since 1.0
*/
public Polygon(int xpoints[], int ypoints[], int npoints) {
// Fix 4489009: should throw IndexOutofBoundsException instead
// of OutofMemoryException if npoints is huge and > {x,y}points.length
if (npoints > xpoints.length || npoints > ypoints.length) {
throw new IndexOutOfBoundsException("npoints > xpoints.length || "+
"npoints > ypoints.length");
}
// Fix 6191114: should throw NegativeArraySizeException with
// negative npoints
if (npoints < 0) {
throw new NegativeArraySizeException("npoints < 0");
}
// Fix 6343431: Applet compatibility problems if arrays are not
// exactly npoints in length
this.npoints = npoints;
this.xpoints = Arrays.copyOf(xpoints, npoints);
this.ypoints = Arrays.copyOf(ypoints, npoints);
}
/**
* Resets this <code>Polygon object to an empty polygon.
* The coordinate arrays and the data in them are left untouched
* but the number of points is reset to zero to mark the old
* vertex data as invalid and to start accumulating new vertex
* data at the beginning.
* All internally-cached data relating to the old vertices
* are discarded.
* Note that since the coordinate arrays from before the reset
* are reused, creating a new empty <code>Polygon might
* be more memory efficient than resetting the current one if
* the number of vertices in the new polygon data is significantly
* smaller than the number of vertices in the data from before the
* reset.
* @see java.awt.Polygon#invalidate
* @since 1.4
*/
public void reset() {
npoints = 0;
bounds = null;
}
/**
* Invalidates or flushes any internally-cached data that depends
* on the vertex coordinates of this <code>Polygon.
* This method should be called after any direct manipulation
* of the coordinates in the <code>xpoints or
* <code>ypoints arrays to avoid inconsistent results
* from methods such as <code>getBounds or contains
* that might cache data from earlier computations relating to
* the vertex coordinates.
* @see java.awt.Polygon#getBounds
* @since 1.4
*/
public void invalidate() {
bounds = null;
}
/**
* Translates the vertices of the <code>Polygon by
* <code>deltaX along the x axis and by
* <code>deltaY along the y axis.
* @param deltaX the amount to translate along the X axis
* @param deltaY the amount to translate along the Y axis
* @since 1.1
*/
public void translate(int deltaX, int deltaY) {
for (int i = 0; i < npoints; i++) {
xpoints[i] += deltaX;
ypoints[i] += deltaY;
}
if (bounds != null) {
bounds.translate(deltaX, deltaY);
}
}
/*
* Calculates the bounding box of the points passed to the constructor.
* Sets <code>bounds to the result.
* @param xpoints[] array of <i>x coordinates
* @param ypoints[] array of <i>y coordinates
* @param npoints the total number of points
*/
void calculateBounds(int xpoints[], int ypoints[], int npoints) {
int boundsMinX = Integer.MAX_VALUE;
int boundsMinY = Integer.MAX_VALUE;
int boundsMaxX = Integer.MIN_VALUE;
int boundsMaxY = Integer.MIN_VALUE;
for (int i = 0; i < npoints; i++) {
int x = xpoints[i];
boundsMinX = Math.min(boundsMinX, x);
boundsMaxX = Math.max(boundsMaxX, x);
int y = ypoints[i];
boundsMinY = Math.min(boundsMinY, y);
boundsMaxY = Math.max(boundsMaxY, y);
}
bounds = new Rectangle(boundsMinX, boundsMinY,
boundsMaxX - boundsMinX,
boundsMaxY - boundsMinY);
}
/*
* Resizes the bounding box to accommodate the specified coordinates.
* @param x, y the specified coordinates
*/
void updateBounds(int x, int y) {
if (x < bounds.x) {
bounds.width = bounds.width + (bounds.x - x);
bounds.x = x;
}
else {
bounds.width = Math.max(bounds.width, x - bounds.x);
// bounds.x = bounds.x;
}
if (y < bounds.y) {
bounds.height = bounds.height + (bounds.y - y);
bounds.y = y;
}
else {
bounds.height = Math.max(bounds.height, y - bounds.y);
// bounds.y = bounds.y;
}
}
/**
* Appends the specified coordinates to this <code>Polygon.
* <p>
* If an operation that calculates the bounding box of this
* <code>Polygon has already been performed, such as
* <code>getBounds or contains, then this
* method updates the bounding box.
* @param x the specified X coordinate
* @param y the specified Y coordinate
* @see java.awt.Polygon#getBounds
* @see java.awt.Polygon#contains
* @since 1.0
*/
public void addPoint(int x, int y) {
if (npoints >= xpoints.length || npoints >= ypoints.length) {
int newLength = npoints * 2;
// Make sure that newLength will be greater than MIN_LENGTH and
// aligned to the power of 2
if (newLength < MIN_LENGTH) {
newLength = MIN_LENGTH;
} else if ((newLength & (newLength - 1)) != 0) {
newLength = Integer.highestOneBit(newLength);
}
xpoints = Arrays.copyOf(xpoints, newLength);
ypoints = Arrays.copyOf(ypoints, newLength);
}
xpoints[npoints] = x;
ypoints[npoints] = y;
npoints++;
if (bounds != null) {
updateBounds(x, y);
}
}
/**
* Gets the bounding box of this <code>Polygon.
* The bounding box is the smallest {@link Rectangle} whose
* sides are parallel to the x and y axes of the
* coordinate space, and can completely contain the <code>Polygon.
* @return a <code>Rectangle that defines the bounds of this
* <code>Polygon.
* @since 1.1
*/
public Rectangle getBounds() {
return getBoundingBox();
}
/**
* Returns the bounds of this <code>Polygon.
* @return the bounds of this <code>Polygon.
* @deprecated As of JDK version 1.1,
* replaced by <code>getBounds().
* @since 1.0
*/
@Deprecated
public Rectangle getBoundingBox() {
if (npoints == 0) {
return new Rectangle();
}
if (bounds == null) {
calculateBounds(xpoints, ypoints, npoints);
}
return bounds.getBounds();
}
/**
* Determines whether the specified {@link Point} is inside this
* <code>Polygon.
* @param p the specified <code>Point to be tested
* @return <code>true if the Polygon contains the
* <code>Point; false otherwise.
* @see #contains(double, double)
* @since 1.0
*/
public boolean contains(Point p) {
return contains(p.x, p.y);
}
/**
* Determines whether the specified coordinates are inside this
* <code>Polygon.
* <p>
* @param x the specified X coordinate to be tested
* @param y the specified Y coordinate to be tested
* @return {@code true} if this {@code Polygon} contains
* the specified coordinates {@code (x,y)};
* {@code false} otherwise.
* @see #contains(double, double)
* @since 1.1
*/
public boolean contains(int x, int y) {
return contains((double) x, (double) y);
}
/**
* Determines whether the specified coordinates are contained in this
* <code>Polygon.
* @param x the specified X coordinate to be tested
* @param y the specified Y coordinate to be tested
* @return {@code true} if this {@code Polygon} contains
* the specified coordinates {@code (x,y)};
* {@code false} otherwise.
* @see #contains(double, double)
* @deprecated As of JDK version 1.1,
* replaced by <code>contains(int, int).
* @since 1.0
*/
@Deprecated
public boolean inside(int x, int y) {
return contains((double) x, (double) y);
}
/**
* {@inheritDoc}
* @since 1.2
*/
public Rectangle2D getBounds2D() {
return getBounds();
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean contains(double x, double y) {
if (npoints <= 2 || !getBoundingBox().contains(x, y)) {
return false;
}
int hits = 0;
int lastx = xpoints[npoints - 1];
int lasty = ypoints[npoints - 1];
int curx, cury;
// Walk the edges of the polygon
for (int i = 0; i < npoints; lastx = curx, lasty = cury, i++) {
curx = xpoints[i];
cury = ypoints[i];
if (cury == lasty) {
continue;
}
int leftx;
if (curx < lastx) {
if (x >= lastx) {
continue;
}
leftx = curx;
} else {
if (x >= curx) {
continue;
}
leftx = lastx;
}
double test1, test2;
if (cury < lasty) {
if (y < cury || y >= lasty) {
continue;
}
if (x < leftx) {
hits++;
continue;
}
test1 = x - curx;
test2 = y - cury;
} else {
if (y < lasty || y >= cury) {
continue;
}
if (x < leftx) {
hits++;
continue;
}
test1 = x - lastx;
test2 = y - lasty;
}
if (test1 < (test2 / (lasty - cury) * (lastx - curx))) {
hits++;
}
}
return ((hits & 1) != 0);
}
private Crossings getCrossings(double xlo, double ylo,
double xhi, double yhi)
{
Crossings cross = new Crossings.EvenOdd(xlo, ylo, xhi, yhi);
int lastx = xpoints[npoints - 1];
int lasty = ypoints[npoints - 1];
int curx, cury;
// Walk the edges of the polygon
for (int i = 0; i < npoints; i++) {
curx = xpoints[i];
cury = ypoints[i];
if (cross.accumulateLine(lastx, lasty, curx, cury)) {
return null;
}
lastx = curx;
lasty = cury;
}
return cross;
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean contains(Point2D p) {
return contains(p.getX(), p.getY());
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean intersects(double x, double y, double w, double h) {
if (npoints <= 0 || !getBoundingBox().intersects(x, y, w, h)) {
return false;
}
Crossings cross = getCrossings(x, y, x+w, y+h);
return (cross == null || !cross.isEmpty());
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean intersects(Rectangle2D r) {
return intersects(r.getX(), r.getY(), r.getWidth(), r.getHeight());
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean contains(double x, double y, double w, double h) {
if (npoints <= 0 || !getBoundingBox().intersects(x, y, w, h)) {
return false;
}
Crossings cross = getCrossings(x, y, x+w, y+h);
return (cross != null && cross.covers(y, y+h));
}
/**
* {@inheritDoc}
* @since 1.2
*/
public boolean contains(Rectangle2D r) {
return contains(r.getX(), r.getY(), r.getWidth(), r.getHeight());
}
/**
* Returns an iterator object that iterates along the boundary of this
* <code>Polygon and provides access to the geometry
* of the outline of this <code>Polygon. An optional
* {@link AffineTransform} can be specified so that the coordinates
* returned in the iteration are transformed accordingly.
* @param at an optional <code>AffineTransform to be applied to the
* coordinates as they are returned in the iteration, or
* <code>null if untransformed coordinates are desired
* @return a {@link PathIterator} object that provides access to the
* geometry of this <code>Polygon.
* @since 1.2
*/
public PathIterator getPathIterator(AffineTransform at) {
return new PolygonPathIterator(this, at);
}
/**
* Returns an iterator object that iterates along the boundary of
* the <code>Shape and provides access to the geometry of the
* outline of the <code>Shape. Only SEG_MOVETO, SEG_LINETO, and
* SEG_CLOSE point types are returned by the iterator.
* Since polygons are already flat, the <code>flatness parameter
* is ignored. An optional <code>AffineTransform can be specified
* in which case the coordinates returned in the iteration are transformed
* accordingly.
* @param at an optional <code>AffineTransform to be applied to the
* coordinates as they are returned in the iteration, or
* <code>null if untransformed coordinates are desired
* @param flatness the maximum amount that the control points
* for a given curve can vary from colinear before a subdivided
* curve is replaced by a straight line connecting the
* endpoints. Since polygons are already flat the
* <code>flatness parameter is ignored.
* @return a <code>PathIterator object that provides access to the
* <code>Shape object's geometry.
* @since 1.2
*/
public PathIterator getPathIterator(AffineTransform at, double flatness) {
return getPathIterator(at);
}
class PolygonPathIterator implements PathIterator {
Polygon poly;
AffineTransform transform;
int index;
public PolygonPathIterator(Polygon pg, AffineTransform at) {
poly = pg;
transform = at;
if (pg.npoints == 0) {
// Prevent a spurious SEG_CLOSE segment
index = 1;
}
}
/**
* Returns the winding rule for determining the interior of the
* path.
* @return an integer representing the current winding rule.
* @see PathIterator#WIND_NON_ZERO
*/
public int getWindingRule() {
return WIND_EVEN_ODD;
}
/**
* Tests if there are more points to read.
* @return <code>true if there are more points to read;
* <code>false otherwise.
*/
public boolean isDone() {
return index > poly.npoints;
}
/**
* Moves the iterator forwards, along the primary direction of
* traversal, to the next segment of the path when there are
* more points in that direction.
*/
public void next() {
index++;
}
/**
* Returns the coordinates and type of the current path segment in
* the iteration.
* The return value is the path segment type:
* SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
* A <code>float array of length 2 must be passed in and
* can be used to store the coordinates of the point(s).
* Each point is stored as a pair of <code>float x, y
* coordinates. SEG_MOVETO and SEG_LINETO types return one
* point, and SEG_CLOSE does not return any points.
* @param coords a <code>float array that specifies the
* coordinates of the point(s)
* @return an integer representing the type and coordinates of the
* current path segment.
* @see PathIterator#SEG_MOVETO
* @see PathIterator#SEG_LINETO
* @see PathIterator#SEG_CLOSE
*/
public int currentSegment(float[] coords) {
if (index >= poly.npoints) {
return SEG_CLOSE;
}
coords[0] = poly.xpoints[index];
coords[1] = poly.ypoints[index];
if (transform != null) {
transform.transform(coords, 0, coords, 0, 1);
}
return (index == 0 ? SEG_MOVETO : SEG_LINETO);
}
/**
* Returns the coordinates and type of the current path segment in
* the iteration.
* The return value is the path segment type:
* SEG_MOVETO, SEG_LINETO, or SEG_CLOSE.
* A <code>double array of length 2 must be passed in and
* can be used to store the coordinates of the point(s).
* Each point is stored as a pair of <code>double x, y
* coordinates.
* SEG_MOVETO and SEG_LINETO types return one point,
* and SEG_CLOSE does not return any points.
* @param coords a <code>double array that specifies the
* coordinates of the point(s)
* @return an integer representing the type and coordinates of the
* current path segment.
* @see PathIterator#SEG_MOVETO
* @see PathIterator#SEG_LINETO
* @see PathIterator#SEG_CLOSE
*/
public int currentSegment(double[] coords) {
if (index >= poly.npoints) {
return SEG_CLOSE;
}
coords[0] = poly.xpoints[index];
coords[1] = poly.ypoints[index];
if (transform != null) {
transform.transform(coords, 0, coords, 0, 1);
}
return (index == 0 ? SEG_MOVETO : SEG_LINETO);
}
}
}
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