说说geotools中坐标转换那点事

概述：
本文说说geotools中坐标转换的那点事情，以WGS84和web墨卡托相互转换为例。
效果：
转换前
转换后
单个Geometry转换
实现代码：
package com.lzugis.geotools;

import java.io.File;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;

import org.geotools.data.FeatureWriter;
import org.geotools.data.FileDataStoreFactorySpi;
import org.geotools.data.Transaction;
import org.geotools.data.shapefile.ShapefileDataStore;
import org.geotools.data.shapefile.ShapefileDataStoreFactory;
import org.geotools.data.simple.SimpleFeatureIterator;
import org.geotools.data.simple.SimpleFeatureSource;
import org.geotools.feature.simple.SimpleFeatureTypeBuilder;
import org.geotools.geometry.jts.JTS;
import org.geotools.geometry.jts.JTSFactoryFinder;
import org.geotools.referencing.CRS;
import org.geotools.referencing.crs.DefaultGeographicCRS;
import org.opengis.feature.simple.SimpleFeature;
import org.opengis.feature.simple.SimpleFeatureType;
import org.opengis.referencing.crs.CoordinateReferenceSystem;
import org.opengis.referencing.operation.MathTransform;

import com.vividsolutions.jts.geom.Geometry;
import com.vividsolutions.jts.geom.GeometryFactory;
import com.vividsolutions.jts.io.WKTReader;
import com.vividsolutions.jts.io.WKTWriter;

public class ProjectTrans {
	private static GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory( null );  
	private static WKTReader reader = new WKTReader( geometryFactory ); 
	private static WKTWriter write = new WKTWriter();  
	static ProjectTrans proj = new ProjectTrans();
	
	
	final String strWKTMercator = "PROJCS["World_Mercator","
            + "GEOGCS["GCS_WGS_1984","
            + "DATUM["WGS_1984","
            + "SPHEROID["WGS_1984",6378137,298.257223563]],"
            + "PRIMEM["Greenwich",0],"
            + "UNIT["Degree",0.017453292519943295]],"
            + "PROJECTION["Mercator_1SP"],"
            + "PARAMETER["False_Easting",0],"
            + "PARAMETER["False_Northing",0],"
            + "PARAMETER["Central_Meridian",0],"
            + "PARAMETER["latitude_of_origin",0],"
            + "UNIT["Meter",1]]";
	/**
	 * 经纬度转WEB墨卡托
	 * @param geom
	 * @return
	 */
	public Geometry lonlat2WebMactor(Geometry geom){
		try{
			//这里是以OGC WKT形式定义的是World Mercator投影，网页地图一般使用该投影
	        
//			CoordinateReferenceSystem crsTarget = CRS.parseWKT(strWKTMercator);
	        CoordinateReferenceSystem crsTarget = CRS.decode("EPSG:3857");
	        
	        // 投影转换
	        MathTransform transform = CRS.findMathTransform(DefaultGeographicCRS.WGS84, crsTarget);
	        return JTS.transform(geom, transform);
		}
		catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
			return null;
		}
	}
	
	public void projectShape(String inputShp, String outputShp){
		try {
			//源shape文件
			ShapefileDataStore shapeDS = (ShapefileDataStore) new ShapefileDataStoreFactory().createDataStore(new File(inputShp).toURI().toURL());
			//创建目标shape文件对象
			Map<String, Serializable> params = new HashMap<String, Serializable>();
	        FileDataStoreFactorySpi factory = new ShapefileDataStoreFactory();
	        params.put(ShapefileDataStoreFactory.URLP.key, new File(outputShp).toURI().toURL());
	        ShapefileDataStore ds = (ShapefileDataStore) factory.createNewDataStore(params);
	        // 设置属性
	        SimpleFeatureSource fs = shapeDS.getFeatureSource(shapeDS.getTypeNames()[0]);
	        //下面这行还有其他写法，根据源shape文件的simpleFeatureType可以不用retype，而直接用fs.getSchema设置
	        CoordinateReferenceSystem crs = CRS.parseWKT(strWKTMercator);
	        ds.createSchema(SimpleFeatureTypeBuilder.retype(fs.getSchema(), crs));
	        
	        //设置writer
	        FeatureWriter<SimpleFeatureType, SimpleFeature> writer = ds.getFeatureWriter(ds.getTypeNames()[0], Transaction.AUTO_COMMIT);
	        
	        //写记录
	        SimpleFeatureIterator it = fs.getFeatures().features();
	        try {
	            while (it.hasNext()) {
	                SimpleFeature f = it.next();
	                SimpleFeature fNew = writer.next();
	                fNew.setAttributes(f.getAttributes());
	                Geometry geom = proj.lonlat2WebMactor((Geometry)f.getAttribute("the_geom"));
	                fNew.setAttribute("the_geom", geom);
	            }
	        } 
	        finally {
	            it.close();
	        }
	        writer.write();
	        writer.close();
	        ds.dispose();
	        shapeDS.dispose();
		} 
		catch (Exception e) { 
			e.printStackTrace();	
		}
	}
	
	
	/**
	 * 工具类测试方法
	 * @param args
	 */
	public static void main(String[] args){
		String wktPoint = "POINT(100.02715479879 33.462715497945)";  
		String wktLine = "LINESTRING(108.32803893589 41.306670233001,99.950999898452 25.84722546391)";  
		String wktPolygon = "POLYGON((100.02715479879 32.168082192159,102.76873121104 37.194305614622,107.0334056301 34.909658604412,105.96723702534 30.949603786713,100.02715479879 32.168082192159))";  
		try {
			long start = System.currentTimeMillis();
			
			Geometry geom1 = (Geometry) reader.read(wktPoint);
			Geometry geom1T = proj.lonlat2WebMactor(geom1);
			
			Geometry geom2 = (Geometry) reader.read(wktLine);
			Geometry geom2T = proj.lonlat2WebMactor(geom2);
			
			Geometry geom3 = (Geometry) reader.read(wktPolygon);
			Geometry geom3T = proj.lonlat2WebMactor(geom3);
			
			System.out.println(write.write(geom1T));  
			System.out.println(write.write(geom2T));
			System.out.println(write.write(geom3T));
			String inputShp = "D:\data\beijing\China4326.shp",
					outputShp = "D:\data\beijing\China3857.shp";
			proj.projectShape(inputShp, outputShp);
			System.out.println("坐标转换完成，共耗时"+(System.currentTimeMillis() - start)+"ms");
		} 
		catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}