Added option to get children and parent tiles.

src/TilesMath/Tile.cs

@@ -54,6 +54,52 @@ private Tile(int x, int y, byte zoom)
     /// </summary>
     public TileNeighbours Neighbours => new TileNeighbours(this);
 
+    /// <summary>
+    /// The parent tile, if any.
+    /// </summary>
+    public Tile? Parent
+    {
+        get
+        {
+            if (this.Zoom == 0) return null;
+
+            return Tile.Create(this.X / 2, this.Y / 2, this.Zoom - 1);
+        }
+    }
+
+    /// <summary>
+    /// The children.
+    /// </summary>
+    public TileChildren Children => new TileChildren(this);
+
+    public IEnumerable<Tile> ChildrenAtZoom(int zoom)
+    {
+        if (zoom < this.Zoom) throw new Exception("Cannot calculate sub tiles for a smaller zoom level");
+
+        if (zoom == this.Zoom)
+        {
+            yield return this;
+            yield break;
+        }
+
+        if (zoom - 1 == this.Zoom)
+        {
+            foreach (var child in this.Children)
+            {
+                yield return child;
+            }
+            yield break;
+        }
+
+        foreach (var childOneLevelLess in this.ChildrenAtZoom(zoom - 1))
+        {
+            foreach (var child in childOneLevelLess.Children)
+            {
+                yield return child;
+            }
+        }
+    }
+
     /// <summary>
     /// Creates a new tile from x-y coordinate and zoom level.
     /// </summary>

src/TilesMath/TileChildren.cs

@@ -0,0 +1,31 @@
+using System.Collections;
+
+namespace TilesMath;
+
+public struct TileChildren : IEnumerable<Tile>
+{
+    private readonly int _x;
+    private readonly int _y;
+    private readonly int _z;
+
+    internal TileChildren(Tile tile)
+    {
+        _x = tile.X * 2;
+        _y = tile.Y * 2;
+        _z = tile.Zoom + 1;
+    }
+
+
+    public IEnumerator<Tile> GetEnumerator()
+    {
+        yield return Tile.Create(_x, _y, _z);
+        yield return Tile.Create(_x + 1, _y, _z);
+        yield return Tile.Create(_x + 1, _y + 1, _z);
+        yield return Tile.Create(_x, _y + 1, _z);
+    }
+
+    IEnumerator IEnumerable.GetEnumerator()
+    {
+        return GetEnumerator();
+    }
+}

src/TilesMath/TilesMath.csproj

@@ -4,7 +4,7 @@
     <TargetFramework>net6.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <PackageVersion>0.0.1</PackageVersion>
+    <PackageVersion>0.0.2</PackageVersion>
     <Title>TilesMath</Title>
     <Authors>ANYWAYS BV</Authors>
     <Description>A tiny library for tiles math.</Description>