Fix misplacement of geometry parts (#30)

* Reset currentX and currentY when encoded data is not written * Add provided unit test slightly modified * Check extent of polygon's interior rings prior to encoding * Add extent test for lineal geometries * Fix failure case * Improve performance when writing MBTiles (#31) * Write encoded geometries directly to the destination list * If id is ulong use it directly * Reset currentX and currentY when encoded data is not written * Add provided unit test slightly modified * Check extent of polygon's interior rings prior to encoding * Add extent test for lineal geometries * Add min[Lineal|Polygonal]Extent to MapBoxTileWriter * Add ExtentInPixels to TileGeometryTransform * Add HasValidExtent functions to EncodeTo functions for lineal and polygonal geometries * Expose default values for min[Lineal|Polygonal]Extent and idAttributeName * Add unit test for min[Lineal|Polygonal]Extent * Fix GitHub Actions criticism * Update README.md * Update frameworks * Update action versions closes #29 --------- Co-authored-by: Dave Leaver <danzel@localhost.geek.nz>
NetTopologySuite · Aug 14, 2024 · 437d29e · 437d29e
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diff --git a/.github/workflows/dotnetcore.yml b/.github/workflows/dotnetcore.yml
@@ -19,10 +19,10 @@ jobs:
 
     steps:
     - name: Get source
-      uses: actions/checkout@v1
+      uses: actions/checkout@v4
 
     - name: Setup .NET Core 6.
-      uses: actions/setup-dotnet@v1
+      uses: actions/setup-dotnet@v4
       with:
         dotnet-version: 6.0.x
 

diff --git a/.github/workflows/prerelease.yml b/.github/workflows/prerelease.yml
@@ -11,11 +11,11 @@ jobs:
 
     steps:
     - name: Get source
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         submodules: 'true'
     - name: Setup .NET Core 6.
-      uses: actions/setup-dotnet@v1
+      uses: actions/setup-dotnet@v4
       with:
         dotnet-version: 6.0.x
     - name: Restore packages.

diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
@@ -11,11 +11,11 @@ jobs:
 
     steps:
     - name: Get source
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
       with:
         submodules: 'true'
     - name: Setup .NET Core 6.
-      uses: actions/setup-dotnet@v1
+      uses: actions/setup-dotnet@v4
       with:
         dotnet-version: 6.0.x
     - name: Restore packages.

diff --git a/README.md b/README.md
@@ -8,7 +8,7 @@ A package that can be used to read or generate vector tiles using NTS.
 
 ## Getting started
 
-This package is somewhat experimental. A NuGet-package is hosted on [Github Packages](https://github.com/orgs/NetTopologySuite/packages?repo_name=NetTopologySuite.IO.VectorTiles) 
+A NuGet-package is hosted on [Github Packages](https://github.com/orgs/NetTopologySuite/packages?repo_name=NetTopologySuite.IO.VectorTiles) 
 
 ### Create a vector tile
 
@@ -34,10 +34,19 @@ vt.Layers.Add(lyr);
 using (var fs = new FileStream(filePath, FileMode.Create))
 {
     //Write the tile to the stream.
-    vt.Write(fs);
+    vt.Write(fs, MapboxTileWriter.DefaultMinLinealExtent, MapboxTileWriter.DefaultMinPolygonalExtent);
 }
 ```
 
+`MapboxTileWriter.Write` method takes two arguments controlling the output of features.
+
+Argument | Default | Meaning
+--- | --- | ---
+minLinealExtent | 1 pixel |This applies to features with lineal geometries. If their scaled geometries for this tile have a bounding box with both edge lengths less than this value will not be written
+minPolygonalExtent | 2 pixel<sup>2</sup> | This applies to polygonal geometries. If their scaled geometries for this tile have a bounding box with an area less than this value will not be exported.
+
+Both constraints apply to parts of geometries, too. Holes in polygons or parts of multi-geometries not meeting the requirement will be omitted.
+
 ### Read a vector tile
 
 The following shows how to read an individual vector tile and access the underlying NTS Features.
@@ -127,10 +136,10 @@ vt.Layers.Add(lyr);
 using (var fs = new FileStream(filePath, FileMode.Create))
 {
     //Write the tile to the stream. This will automatically look for an "id" attribute that is a ulong or integer value as set the tile's feature ID to it.
-    vt.Write(fs);
+    vt.Write(fs, MapboxTileWriter.DefaultMinLinealExtent, MapboxTileWriter.DefaultMinPolygonalExtent);
 
     //Alternatively, pass in a different attribute name to have the vector tiles feature use that ID value.
-    //vt.Write(fs, 4096, "alternateId");
+    //vt.Write(fs, MapboxTileWriter.DefaultMinLinealExtent, MapboxTileWriter.DefaultMinPolygonalExtent, 4096, "alternateId");
 }
 ```
 

diff --git a/src/NetTopologySuite.IO.VectorTiles.Mapbox/MapboxTileWriter.cs b/src/NetTopologySuite.IO.VectorTiles.Mapbox/MapboxTileWriter.cs
@@ -9,14 +9,43 @@ namespace NetTopologySuite.IO.VectorTiles.Mapbox
     // see: https://github.com/mapbox/vector-tile-spec/tree/master/2.1
     public static class MapboxTileWriter
     {
+        /// <summary>
+        /// The default minimum edge length (in pixel) of a lineal feature's extent
+        /// </summary>
+        public const uint DefaultMinLinealExtent = 1;
+
+        /// <summary>
+        /// The default minimum area (in square pixel) of a lineal feature's extent
+        /// </summary>
+        public const uint DefaultMinPolygonalExtent = 2;
+
+        /// <summary>
+        /// The default attribute name of a feature's identifier
+        /// </summary>
+        public const string DefaultIdAttributeName = "id";
+
         /// <summary>
         /// Writes the tiles in a /z/x/y.mvt folder structure.
         /// </summary>
         /// <param name="tree">The tree.</param>
         /// <param name="path">The path.</param>
         /// <param name="extent">The extent.</param>
         /// <remarks>Replaces the files if they are already present.</remarks>
+        [Obsolete("Use overload that can specify minLineal- and minPolygonalExtent")]
         public static void Write(this VectorTileTree tree, string path, uint extent = 4096)
+            => Write(tree, path, DefaultMinLinealExtent, DefaultMinPolygonalExtent, extent, DefaultIdAttributeName);
+
+        /// <summary>
+        /// Writes the tiles in a /z/x/y.mvt folder structure.
+        /// </summary>
+        /// <param name="tree">The tree.</param>
+        /// <param name="path">The path.</param>
+        /// <param name="minLinealExtent">The minimum length in pixel one of a lineal feature's extent edges has to have in order for the feature to be written. The default is 1.</param>
+        /// <param name="minPolygonalExtent">The minimum area in pixel one of a polygonal feature's extent has to have in order for the feature to be written. The default is 2.</param>
+        /// <param name="extent">The extent.</param>
+        /// <remarks>Replaces the files if they are already present.</remarks>
+        public static void Write(this VectorTileTree tree, string path, uint minLinealExtent, uint minPolygonalExtent,
+            uint extent = 4096, string idAttributeName = DefaultIdAttributeName)
         {
             IEnumerable<VectorTile> GetTiles()
             {
@@ -26,7 +55,7 @@ IEnumerable<VectorTile> GetTiles()
                 }
             }
 
-            GetTiles().Write(path, extent);
+            GetTiles().Write(path, minLinealExtent, minPolygonalExtent, extent, idAttributeName);
         }
 
         /// <summary>
@@ -36,7 +65,21 @@ IEnumerable<VectorTile> GetTiles()
         /// <param name="path">The path.</param>
         /// <param name="extent">The extent.</param>
         /// <remarks>Replaces the files if they are already present.</remarks>
+        [Obsolete("Use overload that can specify minLineal- and minPolygonalExtent")]
         public static void Write(this IEnumerable<VectorTile> vectorTiles, string path, uint extent = 4096)
+            => Write(vectorTiles, path, DefaultMinLinealExtent, DefaultMinPolygonalExtent, extent, DefaultIdAttributeName);
+
+        /// <summary>
+        /// Writes the tiles in a /z/x/y.mvt folder structure.
+        /// </summary>
+        /// <param name="vectorTiles">The tiles.</param>
+        /// <param name="path">The path.</param>
+        /// <param name="minLinealExtent">The minimum length in pixel one of a lineal feature's extent edges has to have in order for the feature to be written. The default is 1.</param>
+        /// <param name="minPolygonalExtent">The minimum area in pixel one of a polygonal feature's extent has to have in order for the feature to be written. The default is 2.</param>
+        /// <param name="extent">The extent.</param>
+        /// <remarks>Replaces the files if they are already present.</remarks>
+        public static void Write(this IEnumerable<VectorTile> vectorTiles, string path, uint minLinealExtent, uint minPolygonalExtent,
+            uint extent = 4096, string idAttributeName = DefaultIdAttributeName)
         {
             foreach (var vectorTile in vectorTiles)
             {
@@ -54,7 +97,7 @@ public static void Write(this IEnumerable<VectorTile> vectorTiles, string path,
                 string file = Path.Combine(xFolder, $"{tile.Y}.mvt");
 
                 using var stream = File.Open(file, FileMode.Create);
-                vectorTile.Write(stream, extent);
+                vectorTile.Write(stream, minLinealExtent, minPolygonalExtent, extent, idAttributeName);
             }
         }
 
@@ -65,8 +108,25 @@ public static void Write(this IEnumerable<VectorTile> vectorTiles, string path,
         /// <param name="stream">The stream to write to.</param>
         /// <param name="extent">The extent.</param>
         /// <param name="idAttributeName">The name of an attribute property to use as the ID for the Feature. Vector tile feature ID's should be integer or ulong numbers.</param>
+        [Obsolete("Use overload that can specify minLineal- and minPolygonalExtent")]
         public static void Write(this VectorTile vectorTile, Stream stream, uint extent = 4096, string idAttributeName = "id")
+            => Write(vectorTile, stream, DefaultMinLinealExtent, DefaultMinPolygonalExtent, extent, idAttributeName);
+
+        /// <summary>
+        /// Writes the tile to the given stream.
+        /// </summary>
+        /// <param name="vectorTile">The vector tile.</param>
+        /// <param name="stream">The stream to write to.</param>
+        /// <param name="minLinealExtent">The minimum length in pixel one of a lineal feature's extent edges has to have in order for the feature to be written. The default is 1.</param>
+        /// <param name="minPolygonalExtent">The minimum area in pixel one of a polygonal feature's extent has to have in order for the feature to be written. The default is 2.</param>
+        /// <param name="extent">The extent.</param>
+        /// <param name="idAttributeName">The name of an attribute property to use as the ID for the Feature. Vector tile feature ID's should be integer or ulong numbers.</param>
+        public static void Write(this VectorTile vectorTile, Stream stream, uint minLinealExtent, uint minPolygonalExtent,
+            uint extent = 4096, string idAttributeName = "id")
         {
+            // ensure valid minimal polygonal extent
+            if (minPolygonalExtent < 1) minPolygonalExtent = 1;
+
             var tile = new Tiles.Tile(vectorTile.TileId);
             var tgt = new TileGeometryTransform(tile, extent);
 
@@ -95,11 +155,11 @@ public static void Write(this VectorTile vectorTile, Stream stream, uint extent
                             break;
                         case ILineal lineal:
                             feature.Type = Tile.GeomType.LineString;
-                            EncodeTo(feature.Geometry, lineal, tgt);
+                            EncodeTo(feature.Geometry, lineal, minLinealExtent, tgt);
                             break;
                         case IPolygonal polygonal:
                             feature.Type = Tile.GeomType.Polygon;
-                            EncodeTo(feature.Geometry, polygonal, tgt, tile.Zoom);
+                            EncodeTo(feature.Geometry, polygonal, minPolygonalExtent, tgt);
                             break;
                         default:
                             feature.Type = Tile.GeomType.Unknown;
@@ -236,37 +296,49 @@ private static void EncodeTo(List<uint> destination, IPuntal puntal, TileGeometr
             destination[moveToIndex] = GenerateCommandInteger(MapboxCommandType.MoveTo, (destination.Count - moveToIndex) / 2);
         }
 
-        private static void EncodeTo(List<uint> destination, ILineal lineal, TileGeometryTransform tgt)
+        private static void EncodeTo(List<uint> destination, ILineal lineal, uint minLinealExtent, TileGeometryTransform tgt)
         {
+            bool HasValidLength((long x, long y) tpl) 
+                => tpl.x >= minLinealExtent || tpl.y >= minLinealExtent;
+
             var geometry = (Geometry)lineal;
             int currentX = 0, currentY = 0;
             for (int i = 0; i < geometry.NumGeometries; i++)
             {
                 var lineString = (LineString)geometry.GetGeometryN(i);
-                EncodeTo(destination, lineString.CoordinateSequence, tgt, ref currentX, ref currentY, false);
+                if (HasValidLength(tgt.ExtentInPixel(lineString.EnvelopeInternal)))
+                    EncodeTo(destination, lineString.CoordinateSequence, tgt, ref currentX, ref currentY, false);
             }
         }
 
-        private static void EncodeTo(List<uint> destination, IPolygonal polygonal, TileGeometryTransform tgt, int zoom)
+        private static void EncodeTo(List<uint> destination, IPolygonal polygonal, uint minPolygonalExtent, TileGeometryTransform tgt)
         {
+            bool HasValidExtent((long x, long y) tpl)
+                => (tpl.x >= minPolygonalExtent && tpl.y > 0) ||
+                   (tpl.x > 0 && tpl.y >= minPolygonalExtent);
+
             var geometry = (Geometry)polygonal;
 
-            //Test the whole polygon geometry is larger than a single pixel.
-            if (tgt.IsGreaterThanOnePixelOfTile(geometry))
+            //Test the whole polygonal geometry has a valid extent.
+            if (HasValidExtent(tgt.ExtentInPixel(geometry.EnvelopeInternal)))
             {
                 int currentX = 0, currentY = 0;
                 for (int i = 0; i < geometry.NumGeometries; i++)
                 {
                     var polygon = (Polygon)geometry.GetGeometryN(i);
 
-                    //Test that individual polygons are larger than a single pixel.
-                    if (!tgt.IsGreaterThanOnePixelOfTile(polygon))
+                    // Test that the exterior ring has a valid extent
+                    if (!HasValidExtent(tgt.ExtentInPixel(polygon.ExteriorRing.EnvelopeInternal)))
                         continue;
 
-                    EncodeTo(destination, polygon.Shell.CoordinateSequence, tgt, ref currentX, ref currentY, true, false);
-                    foreach (var hole in polygon.InteriorRings)
+                    EncodeTo(destination, polygon.ExteriorRing.CoordinateSequence, tgt, ref currentX, ref currentY, true, false);
+                    foreach (var interiorRing in polygon.InteriorRings)
                     {
-                        EncodeTo(destination, hole.CoordinateSequence, tgt, ref currentX, ref currentY, true, true);
+                        // Test that the interior ring has a valid extent.
+                        if (!HasValidExtent(tgt.ExtentInPixel(interiorRing.EnvelopeInternal)))
+                            continue;
+
+                        EncodeTo(destination, interiorRing.CoordinateSequence, tgt, ref currentX, ref currentY, true, true);
                     }
                 }
             }
@@ -284,14 +356,16 @@ private static void EncodeTo(List<uint> destination, CoordinateSequence sequence
             if (count == 0)
                 return;
 
+            // In case we decide to ditch encoded data, we must reset currentX and currentY
+            // or subsequent geometry items will not be positioned correctly.
+            int initialCurrentX = currentX;
+            int initialCurrentY = currentY;
+
             // if we have a ring we need to check orientation
             if (ring)
             {
                 if (ccw != Algorithm.Orientation.IsCCW(sequence))
-                {
-                    sequence = sequence.Copy();
-                    CoordinateSequences.Reverse(sequence);
-                }
+                    sequence = sequence.Reversed();
             }
 
             int initialSize = destination.Count;
@@ -335,6 +409,13 @@ private static void EncodeTo(List<uint> destination, CoordinateSequence sequence
                 if (destination.Count - initialSize - 2 < 4)
                     destination.RemoveRange(initialSize, destination.Count - initialSize);
             }
+
+            // Reset currentX and currentY to intital values if there is no encoded data to return
+            if (destination.Count == initialSize)
+            {
+                currentX = initialCurrentX;
+                currentY = initialCurrentY;
+            }
         }
 
         /*

diff --git a/src/NetTopologySuite.IO.VectorTiles.Mapbox/TileGeometryTransform.cs b/src/NetTopologySuite.IO.VectorTiles.Mapbox/TileGeometryTransform.cs
@@ -105,18 +105,27 @@ public bool IsPointInExtent(int x, int y)
         /// </summary>
         /// <param name="polygon">Polygon to test.</param>
         /// <returns>true if the <paramref name="polygon"/> is greater than 1 pixel in the tile pixel coordinates</returns>
-        public bool IsGreaterThanOnePixelOfTile(Geometry polygon)
+        public bool IsGreaterThanOnePixelOfTile(Geometry geometry)
         {
-            if (polygon.IsEmpty) return false;
+            if (geometry.IsEmpty) return false;
 
-            (double x1, double y1) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(polygon.EnvelopeInternal.MinY, polygon.EnvelopeInternal.MinX), ZoomResolution);
-            (double x2, double y2) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(polygon.EnvelopeInternal.MaxY, polygon.EnvelopeInternal.MaxX), ZoomResolution);
+            var env = geometry.EnvelopeInternal;
+            (double x1, double y1) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(env.MinY, env.MinX), ZoomResolution);
+            (double x2, double y2) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(env.MaxY, env.MaxX), ZoomResolution);
 
             double dx = Math.Abs(x2 - x1);
             double dy = Math.Abs(y2 - y1);
 
             // Both must be greater than 0, and at least one of them needs to be larger than 1. 
             return dx > 0 && dy > 0 && (dx > 1 || dy > 1);
         }
+
+        public (long x, long y) ExtentInPixel(Envelope env)
+        {
+            (long minX, long minY) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(env.MinY, env.MinX), ZoomResolution);
+            (long maxX, long maxY) = WebMercatorHandler.FromMetersToPixels(WebMercatorHandler.LatLonToMeters(env.MaxY, env.MaxX), ZoomResolution);
+
+            return (maxX - minX, maxY - minY);
+        }
     }
 }
diff --git a/test/NetTopologySuite.IO.VectorTiles.Samples/NetTopologySuite.IO.VectorTiles.Samples.csproj b/test/NetTopologySuite.IO.VectorTiles.Samples/NetTopologySuite.IO.VectorTiles.Samples.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
     <CopyRefAssembliesToPublishDirectory>false</CopyRefAssembliesToPublishDirectory>
   </PropertyGroup>
 
@@ -34,7 +34,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="5.0.7" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Razor.RuntimeCompilation" Version="6.0.28" />
     <PackageReference Include="NetTopologySuite.IO.GeoJSON" Version="2.0.2" />
   </ItemGroup>
 

diff --git a/test/NetTopologySuite.IO.VectorTiles.Samples/Startup.cs b/test/NetTopologySuite.IO.VectorTiles.Samples/Startup.cs
@@ -113,7 +113,7 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
 
             tree.GetExtents(out Pages.IndexModel._BBox, out Pages.IndexModel._MinZoom, out Pages.IndexModel._MaxZoom);
 
-            tree.Write("wwwroot/tiles");
+            tree.Write("wwwroot/tiles", MapboxTileWriter.DefaultMinLinealExtent, MapboxTileWriter.DefaultMinPolygonalExtent);
         }
     }
 }
diff --git a/test/NetTopologySuite.IO.VectorTiles.Tests.Functional/Program.cs b/test/NetTopologySuite.IO.VectorTiles.Tests.Functional/Program.cs
@@ -56,7 +56,7 @@ private static void RunTest(string fileName, int minZoom, int maxZoom, string st
             };
 
             // write the tiles to disk as mvt.
-            Mapbox.MapboxTileWriter.Write(tree, "tiles");
+            Mapbox.MapboxTileWriter.Write(tree, "tiles", 1, 2);
 
             stopwatch.Stop();