最小外接矩形

外接矩形計算

對一個凸多邊形進行外接矩形計算，需要知道當前面的最大xy 和最小xy值，即可獲得外接矩形

最小外接矩形計算

對凸多邊形的每一條邊都繪制一個外接矩形求最小面積。下圖展示了計算流程

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計算流程

旋轉基礎算法實現

• 旋轉點基礎

/*** 旋轉點** @param point 被旋轉的點* @param center 旋轉中心* @param angle 角度* @return 旋轉后坐標*/public static Coordinate get(Coordinate point, Coordinate center, double angle) {double cos = Math.cos(angle);double sin = Math.sin(angle);double x = point.x;double y = point.y;double centerX = center.x;double centerY = center.y;return new Coordinate(centerX + cos * (x - centerX) - sin * (y - centerY),centerY + sin * (x - centerX) + cos * (y - centerY));}

凸包算法實現

Geometry hull = (new ConvexHull(geom)).getConvexHull();

獲得結果

public static Polygon get(Geometry geom, GeometryFactory gf) {Geometry hull = (new ConvexHull(geom)).getConvexHull();if (!(hull instanceof Polygon)) {return null;}Polygon convexHull = (Polygon) hull;System.out.println(convexHull);// 直接使用中心值Coordinate c = geom.getCentroid().getCoordinate();System.out.println("==============旋轉基點==============");System.out.println(new GeometryFactory().createPoint(c));System.out.println("==============旋轉基點==============");Coordinate[] coords = convexHull.getExteriorRing().getCoordinates();double minArea = Double.MAX_VALUE;double minAngle = 0;Polygon ssr = null;Coordinate ci = coords[0];Coordinate cii;for (int i = 0; i < coords.length - 1; i++) {cii = coords[i + 1];double angle = Math.atan2(cii.y - ci.y, cii.x - ci.x);Polygon rect = (Polygon) Rotation.get(convexHull, c, -1 * angle, gf).getEnvelope();double area = rect.getArea(); // 此處可以將 rotationPolygon 放到list中求最小值 // Polygon rotationPolygon = Rotation.get(rect, c, angle, gf); // System.out.println(rotationPolygon);if (area < minArea) {minArea = area;ssr = rect;minAngle = angle;}ci = cii;}return Rotation.get(ssr, c, minAngle, gf);}

測試類

@Testpublic void test() throws Exception{GeometryFactory gf = new GeometryFactory();String wkt = "POLYGON ((87623.0828822501 73753.4143904365,87620.1073981973 73739.213216548,87629.1690996309 73730.4220136646,87641.882531493 73727.3112803367,87643.0997749692 73714.8683470248,87662.0346734872 73725.0120426595,87669.0676357939 73735.1557382941,87655.9484561064 73735.9672339449,87676.9120937514 73747.4634223308,87651.8909778525 73740.8362078495,87659.4649372597 73755.4431295634,87644.4522677204 73748.680665807,87645.5342619215 73760.7178512935,87635.2553170117 73750.9799034842,87630.5215923822 73760.3121034681,87623.0828822501 73753.4143904365))";Polygon read = (Polygon) new WKTReader().read(wkt);Polygon polygon = MinimumBoundingRectangle.get(read, gf);// System.out.println(polygon); // System.out.println(polygon.getArea());}

注

本文代碼及可視化代碼均放在 gitee 碼云上 歡迎star & fork

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