射线法判断点是否在多边形内-JAVA

1、定义点

public class Point {private BigDecimal x;private BigDecimal y;public Point() {};@Overridepublic String toString() {DecimalFormat df = new DecimalFormat("#.000000000000000000000000000000");return "Point [x=" + df.format(x) + ", y=" + df.format(y) + "]";}public Point(BigDecimal x, BigDecimal y) {this.x = x;this.y = y;}public BigDecimal getX() {return x;}public void setX(BigDecimal x) {this.x = x;}public BigDecimal getY() {return y;}public void setY(BigDecimal y) {this.y = y;}
}

2、定义线（多边形的边）


public class Line {private Point apoint;private Point zpoint;private BigDecimal k;private BigDecimal b;public Line() {}public Line(Point a, Point z) {this.apoint = a;this.zpoint = z;}public Line(BigDecimal x1, BigDecimal y1, BigDecimal x2, BigDecimal y2) {this.apoint = new Point(x1, y1);this.zpoint = new Point(x2, y2);}/*** 计算中点* * @return*/public Point getMidPoint() {Point midPoint = null;if (apoint != null && zpoint != null) {BigDecimal x = (apoint.getX().add(zpoint.getX())).divide(new BigDecimal(2), PolygonUtil.ACCURACY,BigDecimal.ROUND_HALF_UP);BigDecimal y = (apoint.getY().add(zpoint.getY())).divide(new BigDecimal(2), PolygonUtil.ACCURACY,BigDecimal.ROUND_HALF_UP);midPoint = new Point(x, y);}return midPoint;}/*** 获取斜率* * @return*/public BigDecimal getK() {// k = (y1 - y2) / (x1 - x2)if (k == null) {k = BigDecimal.ZERO;if (apoint != null && zpoint != null) {if (apoint.getX().compareTo(zpoint.getX()) != 0) {k = (apoint.getY().subtract(zpoint.getY())).divide(apoint.getX().subtract(zpoint.getX()),PolygonUtil.ACCURACY, BigDecimal.ROUND_HALF_UP);}}}return k;}public BigDecimal getB() {// b = y - kxif (b == null) {b = BigDecimal.ZERO;if (apoint != null && zpoint != null) {BigDecimal k = getK();if (k.compareTo(BigDecimal.ZERO) == 0) {b = apoint.getY();} else {b = apoint.getY().subtract(apoint.getX().multiply(k));}}}return b;}@Overridepublic String toString() {DecimalFormat df = new DecimalFormat("#.000000000000000000000000000000");return "Line [apoint=" + apoint + ", zpoint=" + zpoint+ ", getMidPoint()=" + getMidPoint() + ", getK()="+ df.format(getK()) + ", getB()=" + df.format(getB())+ ", getApoint()=" + getApoint() + ", getZpoint()="+ getZpoint() + ", getClass()=" + getClass() + ", hashCode()="+ hashCode() + ", toString()=" + super.toString() + "]";}public Point getApoint() {return apoint;}public void setApoint(Point apoint) {this.apoint = apoint;}public Point getZpoint() {return zpoint;}public void setZpoint(Point zpoint) {this.zpoint = zpoint;}
}

3、判断线是否在多边形内

public class PolygonUtil {private final static Logger logger = LoggerFactory.getLogger(GeoService.class);public static final int ACCURACY = 30;/*** 将多边形拆除多条边（此处为超图多边形模型，可根据具体模型修改此方法）* @param polygon* @return*/public List<Line> getLineList(GeoRegion polygon) {List<Line> lines = new ArrayList<Line>();Point2D apt = null;Point2D zpt = null;Point2Ds pts = null;Line line = null;for (int i = 0; i < polygon.getPartCount(); i++) {pts = polygon.getPart(i);for (int j = 0; j < pts.getCount() - 1; j++) {apt = pts.getItem(j);zpt = pts.getItem(j + 1);line = new Line(new BigDecimal(apt.getX()), new BigDecimal(apt.getY()), new BigDecimal(zpt.getX()),new BigDecimal(zpt.getY()));lines.add(line);}}return lines;}/*** 判断点是否在多边形内* * @param point* @param lines* @return*/public boolean withIn(Point point, List<Line> lines) {// 根据面第一条边中点确认射线Line ray = new Line(point, lines.get(0).getMidPoint());Line line = null;Point meetPoint = null;// logger.info(ray.toString());// logger.info(lines.get(0).getMidPoint().toString());// 因为第一条边必定与射线相交，则从第二条边开始判断int count = 1;for (int i = 1; i < lines.size(); i++) {// logger.info("---------------------");line = lines.get(i);meetPoint = getMeetPoint(ray, line);if (line.getK().compareTo(ray.getK()) != 0) {if (isInline(meetPoint, line) && isInRay(meetPoint, ray)) {count++;}}// logger.info(line.toString());// logger.info(meetPoint.toString());}return count % 2 == 0 ? false : true;}/*** 获取交汇点* * @param ray* @param line* @return*/public Point getMeetPoint(Line ray, Line line) {// x = (b1 - b2) / (k2 - k1)// y = kx + bPoint point = null;BigDecimal x = BigDecimal.ZERO;BigDecimal y = BigDecimal.ZERO;// logger.info("KK:{}", line.getK().compareTo(ray.getK()));if (line.getK().compareTo(ray.getK()) != 0) {if (line.getK().compareTo(BigDecimal.ONE) == 0) {x = line.getApoint().getX();} else {x = (ray.getB().subtract(line.getB())).divide(line.getK().subtract(ray.getK()), PolygonUtil.ACCURACY,BigDecimal.ROUND_HALF_UP);}if (line.getK().compareTo(BigDecimal.ZERO) == 0) {y = line.getApoint().getY();} else {y = ray.getK().multiply(x).add(ray.getB());}point = new Point(x, y);}return point;}/*** 判断交汇点是否在线段上* * @param point* @param line* @return*/public boolean isInline(Point point, Line line) {boolean result = false;if (point == null || point.getX() == null || point.getY() == null) {result = false;} else if ((line.getApoint().getX().compareTo(point.getX()) == -1 && line.getZpoint().getX().compareTo(point.getX()) == -1)|| (line.getApoint().getX().compareTo(point.getX()) == 1 && line.getZpoint().getX().compareTo(point.getX()) == 1)|| (line.getApoint().getY().compareTo(point.getY()) == -1 && line.getZpoint().getY().compareTo(point.getY()) == -1)|| (line.getApoint().getY().compareTo(point.getY()) == 1 && line.getZpoint().getY().compareTo(point.getY()) == 1)) {result = false;} else {result = true;}// logger.info("AX:{}",// line.getApoint().getX().compareTo(point.getX()));// logger.info("ZX:{}",// line.getZpoint().getX().compareTo(point.getX()));// logger.info("AY:{}",// line.getApoint().getY().compareTo(point.getY()));// logger.info("ZY:{}",// line.getZpoint().getY().compareTo(point.getY()));// logger.info("RESULT:{}", result);return result;}/*** 判断点是否在射线上* * @param point* @param ray* @return*/public boolean isInRay(Point point, Line ray) {boolean result = false;if (point == null || point.getX() == null || point.getY() == null) {result = false;} else {BigDecimal x = (ray.getApoint().getX().subtract(ray.getZpoint().getX())).multiply(ray.getApoint().getX().subtract(point.getX()));BigDecimal y = (ray.getApoint().getY().subtract(ray.getZpoint().getY())).multiply(ray.getApoint().getY().subtract(point.getY()));if (x.compareTo(new BigDecimal(0)) < 0|| y.compareTo(new BigDecimal(0)) < 0) {result = false;} else {result = true;}}return result;}/*** 测试* @param args*/public static void main(String[] args) {// 组成多边形的边集合List<Line> lines = new ArrayList<Line>();Point a = new Point(new BigDecimal(1D), new BigDecimal(1D));Point b = new Point(new BigDecimal(2D), new BigDecimal(5D));Point c = new Point(new BigDecimal(5D), new BigDecimal(6D));Point d = new Point(new BigDecimal(4D), new BigDecimal(2D));lines.add(new Line(a, b));lines.add(new Line(b, c));lines.add(new Line(c, d));lines.add(new Line(d, a));List<Point> pointList = new ArrayList<Point>();pointList.add(new Point(new BigDecimal(3.1D), new BigDecimal(3.1D)));pointList.add(new Point(new BigDecimal(7D), new BigDecimal(7D)));PolygonUtil test = new PolygonUtil();for (Point point: pointList) {if (test.withIn(point, lines)) {System.out.printf("点在多边形内:%s\n", point.toString());} else {System.out.printf("点不在多边形内:%s\n", point.toString());}}}
}

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