org.argeo.app.core/src/org/argeo/app/geo/GpxUtils.java

   1 package org.argeo.app.geo;
   2
   3 import java.io.IOException;
   4 import java.io.InputStream;
   5 import java.io.OutputStream;
   6 import java.io.OutputStreamWriter;
   7 import java.io.Writer;
   8 import java.nio.charset.StandardCharsets;
   9 import java.util.ArrayList;
  10 import java.util.List;
  11 import java.util.Objects;
  12 import java.util.StringTokenizer;
  13
  14 import javax.xml.parsers.ParserConfigurationException;
  15 import javax.xml.parsers.SAXParser;
  16 import javax.xml.parsers.SAXParserFactory;
  17
  18 import org.geotools.data.DataUtilities;
  19 import org.geotools.feature.SchemaException;
  20 import org.geotools.feature.simple.SimpleFeatureBuilder;
  21 import org.geotools.geometry.jts.JTSFactoryFinder;
  22 import org.locationtech.jts.geom.Coordinate;
  23 import org.locationtech.jts.geom.GeometryFactory;
  24 import org.locationtech.jts.geom.Polygon;
  25 import org.opengis.feature.simple.SimpleFeature;
  26 import org.opengis.feature.simple.SimpleFeatureType;
  27 import org.xml.sax.Attributes;
  28 import org.xml.sax.SAXException;
  29 import org.xml.sax.helpers.DefaultHandler;
  30
  31 /** Utilities around the GPX format. */
  32 public class GpxUtils {
  33
  34         public static SimpleFeature parseGpxToPolygon(InputStream in) throws IOException {
  35                 try {
  36                         final SimpleFeatureType TYPE = DataUtilities.createType("Area", "the_geom:Polygon:srid=4326");
  37                         SimpleFeatureBuilder featureBuilder = new SimpleFeatureBuilder(TYPE);
  38
  39                         GeometryFactory geometryFactory = JTSFactoryFinder.getGeometryFactory();
  40                         List<Coordinate> coordinates = new ArrayList<>();
  41                         SAXParserFactory factory = SAXParserFactory.newInstance();
  42                         SAXParser saxParser = factory.newSAXParser();
  43
  44                         saxParser.parse(in, new DefaultHandler() {
  45
  46                                 @Override
  47                                 public void startElement(String uri, String localName, String qName, Attributes attributes)
  48                                                 throws SAXException {
  49                                         if ("trkpt".equals(qName)) {
  50                                                 Double latitude = Double.parseDouble(attributes.getValue("lat"));
  51                                                 Double longitude = Double.parseDouble(attributes.getValue("lon"));
  52                                                 Coordinate coordinate = new Coordinate(longitude, latitude);
  53                                                 coordinates.add(coordinate);
  54                                         }
  55                                 }
  56
  57                         });
  58                         // close the line string
  59                         coordinates.add(coordinates.get(0));
  60
  61                         Polygon polygon = geometryFactory.createPolygon(coordinates.toArray(new Coordinate[coordinates.size()]));
  62                         featureBuilder.add(polygon);
  63                         SimpleFeature area = featureBuilder.buildFeature(null);
  64                         return area;
  65                 } catch (ParserConfigurationException | SAXException | SchemaException e) {
  66                         throw new RuntimeException("Cannot convert GPX", e);
  67                 }
  68         }
  69
  70         public static void writeGeoShapeAsGpx(String geoShape, OutputStream out) throws IOException {
  71                 Objects.requireNonNull(geoShape);
  72                 Writer writer = new OutputStreamWriter(out, StandardCharsets.UTF_8);
  73                 writer.append("<gpx><trk><trkseg>");
  74                 StringTokenizer stSeg = new StringTokenizer(geoShape.trim(), ";");
  75                 while (stSeg.hasMoreTokens()) {
  76                         StringTokenizer stPt = new StringTokenizer(stSeg.nextToken().trim(), " ");
  77                         String lat = stPt.nextToken();
  78                         String lng = stPt.nextToken();
  79                         String alt = stPt.nextToken();
  80                         // String precision = stPt.nextToken();
  81                         writer.append("<trkpt");
  82                         writer.append(" lat=\"").append(lat).append('\"');
  83                         writer.append(" lon=\"").append(lng).append('\"');
  84                         if (!alt.equals("0.0")) {
  85                                 writer.append('>');
  86                                 writer.append("<ele>").append(alt).append("</ele>");
  87                                 writer.append("</trkpt>");
  88                         } else {
  89                                 writer.append("/>");
  90                         }
  91                 }
  92                 writer.append("</trkseg></trk></gpx>");
  93                 writer.flush();
  94         }
  95
  96         /** Singleton. */
  97         private GpxUtils() {
  98         }
  99 }