java GeoTools实现Geometry对象转换成MultiPolygon

GeoTools是一套操作和显示地图的开源Java 代码库，提供了一系列符合规范的操作地理空间数据的方法，GeoTools被许多项目使用，在地理信息领域有着广泛的应用。

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会跑的小鹿

1051人浏览 · 2023-06-03 16:48:40

会跑的小鹿 · 2023-06-03 16:48:40 发布

一.GeoTools介绍

二.背景

本文介绍的是如何使用GeoTools将Geometry对象转换成MultiPolygon，因为Geometry可以包含点线面多种几何图形，而在进行几何分析时，通常需要面要素，因此我们需要将Geometry中的面提取出来，转换成MultiPolygon，便于后续进行空间分析查询使用。

三.实现代码

1.常规转换

下面定义了一个geometryToMultiPolygon，调用这个方法即可实现Geometry对象转换成MultiPolygon。

public static MultiPolygon geometryToMultiPolygon(Geometry geometry){
       if (geometry == null){
           return null;
       }
       Integer srid = geometry.getSRID();
       String geometryType = geometry.getGeometryType();
       if (geometryType.equals("Polygon")){
           return polygonToMultipolygon((Polygon) geometry);
       }else if (geometryType.equals("MultiPolygon")){
            return (MultiPolygon) geometry;
       }else if (geometryType.equals("GeometryCollection")){
            int numGeometries = geometry.getNumGeometries();
           Geometry geometryChird = null;
           String geoType = null;
           Geometry geometryUnion = null;
           for (int i = 0;i < numGeometries;i++){
                geometryChird = geometry.getGeometryN(i);
               geoType = geometryChird.getGeometryType();
               if (geoType.equals("Polygon") || geoType.equals("MultiPolygon") ){
                   if (geometryUnion == null){
                       geometryUnion = geometryChird;
                   }else {
                       geometryUnion = geometryUnion.union(geometryChird);
                   }
               }
           }
           if (geometryUnion != null){
               geometryUnion.setSRID(srid);
               if (geometryUnion.getGeometryType().equals("MultiPolygon")){
                   return (MultiPolygon) geometryUnion;
               }else {
                   return polygonToMultipolygon((Polygon) geometryUnion);
               }
           }
       }
       return null;
   }

2.设定最小面积转换

在前面的常规简单进行Geometry对象转换成MultiPolygon的情况下，我们还可以指定一个最小面积，是Geometry中达到最小面积的面和微小面实现分离提取。代码如下

public static List<MultiPolygon> geometryToMultiPolygon(Geometry geometry,double minArea){
       List<MultiPolygon> list = new ArrayList<>();
       String geometryType = geometry.getGeometryType();
       if (geometryType.equals("Polygon")){
            Polygon polygon = (Polygon) geometry;
           MultiPolygon multiPolygon = polygonToMultipolygon(polygon);
           if (multiPolygon.getArea() >= minArea){
               list.add(multiPolygon);
               list.add(null);
           }else {
               list.add(null);
               list.add(multiPolygon);
           }
       }else if (geometryType.equals("MultiPolygon")){
            MultiPolygon multiPolygon = (MultiPolygon) geometry;
           if (multiPolygon.getArea() >= minArea){
               list.add(multiPolygon);
               list.add(null);
           }else {
               list.add(null);
               list.add(multiPolygon);
           }
       }else if (geometryType.equals("GeometryCollection")){
            int numGeometries = geometry.getNumGeometries();
           Geometry geometryChird = null;
           String geoType = null;
           Geometry geometryUnionBig = null;
           Geometry geometryUnionSmall = null;
           for (int i = 0;i < numGeometries;i++){
                geometryChird = geometry.getGeometryN(i);
               geoType = geometryChird.getGeometryType();
               if (geoType.equals("Polygon") || geoType.equals("MultiPolygon") ){
                   if (geometryChird.getArea() >= minArea){
                       if (geometryUnionBig == null){
                           geometryUnionBig = geometryChird;
                       }else {
                           geometryUnionBig = geometryUnionBig.union(geometryChird);
                       }
                   }else {
                       if (geometryUnionSmall == null){
                           geometryUnionSmall = geometryChird;
                       }else {
                           geometryUnionSmall = geometryUnionSmall.union(geometryChird);
                       }
                   }
               }
           }
           if (geometryUnionBig != null){
               if (geometryUnionBig.getGeometryType().equals("MultiPolygon")){
                   list.add((MultiPolygon) geometryUnionBig);
               }else {
                   list.add(polygonToMultipolygon((Polygon) geometryUnionBig));
               }
           }else {
               list.add(null);
           }
           if (geometryUnionSmall != null){
               if (geometryUnionSmall.getGeometryType().equals("MultiPolygon")){
                   list.add((MultiPolygon) geometryUnionSmall);
               }else {
                   list.add(polygonToMultipolygon((Polygon) geometryUnionSmall));
               }
           }else {
               list.add(null);
           }
       }else {
           list.add(null);
           list.add(null);
       }
       return list;
   }