tested out building merge

src/main/java/com/onthegomap/flatmap/FeatureMerge.java

@@ -31,11 +31,6 @@ import org.slf4j.LoggerFactory;
 public class FeatureMerge {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(FeatureMerge.class);
-  private static final BufferParameters bufferOps = new BufferParameters();
-
-  static {
-    bufferOps.setJoinStyle(BufferParameters.JOIN_MITRE);
-  }
 
   public static List<VectorTileEncoder.Feature> mergeLineStrings(List<VectorTileEncoder.Feature> items,
     double minLength, double tolerance, double clip) throws GeometryException {
@@ -131,6 +126,12 @@ public class FeatureMerge {
     }
   }
 
+  private static final BufferParameters bufferOps = new BufferParameters();
+
+  static {
+    bufferOps.setJoinStyle(BufferParameters.JOIN_MITRE);
+  }
+
   public static List<VectorTileEncoder.Feature> mergePolygons(List<VectorTileEncoder.Feature> features, double minArea,
     double minDist, double buffer) throws GeometryException {
     List<VectorTileEncoder.Feature> result = new ArrayList<>(features.size());

src/main/java/com/onthegomap/flatmap/profiles/OpenMapTilesProfile.java

@@ -2,9 +2,11 @@ package com.onthegomap.flatmap.profiles;
 
 import com.graphhopper.reader.ReaderRelation;
 import com.onthegomap.flatmap.FeatureCollector;
+import com.onthegomap.flatmap.FeatureMerge;
 import com.onthegomap.flatmap.Profile;
 import com.onthegomap.flatmap.SourceFeature;
 import com.onthegomap.flatmap.VectorTileEncoder;
+import com.onthegomap.flatmap.geo.GeometryException;
 import com.onthegomap.flatmap.read.OpenStreetMapReader;
 import java.util.List;
 import org.slf4j.Logger;
@@ -12,6 +14,8 @@ import org.slf4j.LoggerFactory;
 
 public class OpenMapTilesProfile implements Profile {
 
+  private static boolean MERGE_Z13_BUILDINGS = false;
+
   public static final String LAKE_CENTERLINE_SOURCE = "lake_centerlines";
   public static final String WATER_POLYGON_SOURCE = "water_polygons";
   public static final String NATURAL_EARTH_SOURCE = "natural_earth";
@@ -24,7 +28,10 @@ public class OpenMapTilesProfile implements Profile {
 
   @Override
   public List<VectorTileEncoder.Feature> postProcessLayerFeatures(String layer, int zoom,
-    List<VectorTileEncoder.Feature> items) {
+    List<VectorTileEncoder.Feature> items) throws GeometryException {
+    if (MERGE_Z13_BUILDINGS && "building".equals(layer) && zoom == 13) {
+      return FeatureMerge.mergePolygons(items, 4, 0.5, 0.5);
+    }
     return items;
   }
 
@@ -88,7 +95,7 @@ public class OpenMapTilesProfile implements Profile {
         if (sourceFeature.hasTag("building")) {
           features.polygon("building")
             .setZoomRange(13, 14)
-            .setMinPixelSize(4);
+            .setMinPixelSize(MERGE_Z13_BUILDINGS ? 0 : 4);
         }
       }
     }

src/test/java/com/onthegomap/flatmap/FeatureMergeTest.java

@@ -527,9 +527,9 @@ public class FeatureMergeTest {
 
   @ParameterizedTest
   @CsvSource({
-    "2477, 3028, 13, 876",
-    "2481, 3026, 13, 806",
-    "2479, 3028, 13, 884"
+    "2477, 3028, 13, 1026",
+    "2481, 3026, 13, 789",
+    "2479, 3028, 13, 963"
   })
   public void testMergeManyPolygons(int x, int y, int z, int expected)
     throws IOException, GeometryException {
@@ -537,7 +537,7 @@ public class FeatureMergeTest {
       byte[] tileData = db.getTile(x, y, z);
       byte[] gunzipped = TestUtils.gunzip(tileData);
       List<VectorTileEncoder.Feature> features = VectorTileEncoder.decode(gunzipped);
-      List<VectorTileEncoder.Feature> merged = FeatureMerge.mergePolygons(features, 1, 1, 1);
+      List<VectorTileEncoder.Feature> merged = FeatureMerge.mergePolygons(features, 4, 0.5, 0.5);
       int total = 0;
       for (var feature : merged) {
         Geometry geometry = feature.geometry().decode();