planetiler-openmaptiles/src/main/java/org/openmaptiles/layers/Landuse.java

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*/
package org.openmaptiles.layers;

import static org.openmaptiles.util.Utils.coalesce;
import static org.openmaptiles.util.Utils.nullIfEmpty;

import com.onthegomap.planetiler.FeatureCollector;
import com.onthegomap.planetiler.FeatureMerge;
import com.onthegomap.planetiler.ForwardingProfile;
import com.onthegomap.planetiler.VectorTile;
import com.onthegomap.planetiler.config.PlanetilerConfig;
import com.onthegomap.planetiler.geo.GeometryException;
import com.onthegomap.planetiler.reader.SourceFeature;
import com.onthegomap.planetiler.stats.Stats;
import com.onthegomap.planetiler.util.Parse;
import com.onthegomap.planetiler.util.Translations;
import com.onthegomap.planetiler.util.ZoomFunction;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;
import org.openmaptiles.OpenMapTilesProfile;
import org.openmaptiles.generated.OpenMapTilesSchema;
import org.openmaptiles.generated.Tables;

/**
 * Defines the logic for generating map elements for man-made land use polygons like cemeteries, zoos, and hospitals in
 * the {@code landuse} layer from source features.
 * <p>
 * This class is ported to Java from
 * <a href="https://github.com/openmaptiles/openmaptiles/tree/master/layers/landuse">OpenMapTiles landuse sql files</a>.
 */
public class Landuse implements
  OpenMapTilesSchema.Landuse,
  OpenMapTilesProfile.NaturalEarthProcessor,
  ForwardingProfile.LayerPostProcessor,
  Tables.OsmLandusePolygon.Handler {

  private static final ZoomFunction<Number> MIN_PIXEL_SIZE_THRESHOLDS = ZoomFunction.fromMaxZoomThresholds(Map.of(
    13, 4,
    7, 2,
    6, 1
  ));
  private static final TreeMap<Integer, Double> MINDIST_AND_BUFFER_SIZES = new TreeMap<>(Map.of(
    5, 0.1,
    // there is quite huge jump between Z5:NE and Z6:OSM => bigger generalization needed to make the transition more smooth
    6, 0.5,
    7, 0.25,
    8, 0.125,
    Integer.MAX_VALUE, 0.1
  ));
  private static final Set<String> Z6_CLASSES = Set.of(
    FieldValues.CLASS_RESIDENTIAL,
    FieldValues.CLASS_SUBURB,
    FieldValues.CLASS_QUARTER,
    FieldValues.CLASS_NEIGHBOURHOOD
  );

  public Landuse(Translations translations, PlanetilerConfig config, Stats stats) {}

  @Override
  public void processNaturalEarth(String table, SourceFeature feature, FeatureCollector features) {
    if ("ne_50m_urban_areas".equals(table)) {
      Double scalerank = Parse.parseDoubleOrNull(feature.getTag("scalerank"));
      int minzoom = (scalerank != null && scalerank <= 2) ? 4 : 5;
      features.polygon(LAYER_NAME).setBufferPixels(BUFFER_SIZE)
        .setAttr(Fields.CLASS, FieldValues.CLASS_RESIDENTIAL)
        .setZoomRange(minzoom, 5);
    }
  }

  @Override
  public void process(Tables.OsmLandusePolygon element, FeatureCollector features) {
    String clazz = coalesce(
      nullIfEmpty(element.landuse()),
      nullIfEmpty(element.amenity()),
      nullIfEmpty(element.leisure()),
      nullIfEmpty(element.tourism()),
      nullIfEmpty(element.place()),
      nullIfEmpty(element.waterway())
    );
    if (clazz != null) {
      if ("grave_yard".equals(clazz)) {
        clazz = FieldValues.CLASS_CEMETERY;
      }
      var feature = features.polygon(LAYER_NAME).setBufferPixels(BUFFER_SIZE)
        .setAttr(Fields.CLASS, clazz)
        .setMinZoom(Z6_CLASSES.contains(clazz) ? 6 : 9);
      if (FieldValues.CLASS_RESIDENTIAL.equals(clazz)) {
        feature
          .setMinPixelSize(0.1)
          .setPixelTolerance(0.25);
      } else {
        feature
          .setMinPixelSizeOverrides(MIN_PIXEL_SIZE_THRESHOLDS);
      }
    }
  }

  @Override
  public List<VectorTile.Feature> postProcess(int zoom,
    List<VectorTile.Feature> items) throws GeometryException {
    List<VectorTile.Feature> toMerge = new ArrayList<>();
    List<VectorTile.Feature> result = new ArrayList<>();
    for (var item : items) {
      if (FieldValues.CLASS_RESIDENTIAL.equals(item.tags().get(Fields.CLASS))) {
        toMerge.add(item);
      } else {
        result.add(item);
      }
    }
    List<VectorTile.Feature> merged;
    if (zoom <= 12) {
      double minDistAndBuffer = MINDIST_AND_BUFFER_SIZES.ceilingEntry(zoom).getValue();
      merged = FeatureMerge.mergeNearbyPolygons(toMerge, 1, 1, minDistAndBuffer, minDistAndBuffer);
    } else {
      // reduces size of some heavy z13-14 tiles with lots of small polygons
      merged = FeatureMerge.mergeMultiPolygon(toMerge);
    }
    result.addAll(merged);
    return result;
  }
}