Added countatzoom for tileset.

src/TilesMath/Collections/TileTreeSetExtensions.cs

@@ -31,4 +31,34 @@ public static IEnumerable<Tile> ToEnumerableAtZoom(this TileTreeSet set, int zoo
             }
         }
     }
+
+    /// <summary>
+    /// Calculates the number of tiles at the given zoom level.
+    /// </summary>
+    /// <param name="set">The set.</param>
+    /// <param name="zoom">The zoom level.</param>
+    /// <returns>The number of tiles the set represents at the given zoom.</returns>
+    /// <exception cref="Exception">When tiles are found at a higher zoom level in the set it is not possible to enumerate.</exception>
+    public static long CountAtZoom(this TileTreeSet set, int zoom)
+    {
+        var count = 0L;
+        foreach (var tile in set)
+        {
+            if (tile.Zoom == zoom)
+            {
+                count++;
+            }
+            else if (tile.Zoom < zoom)
+            {
+                count += (long)System.Math.Pow(4, zoom - tile.Zoom);
+            }
+            else
+            {
+                throw new Exception(
+                    $"Cannot enumerate this set at {zoom}, found at tile at a higher zoom level: {tile.Zoom}");
+            }
+        }
+
+        return count;
+    }
 }

src/TilesMath/TilesMath.csproj

@@ -4,7 +4,7 @@
     <TargetFramework>net6.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <PackageVersion>0.0.7</PackageVersion>
+    <PackageVersion>0.0.8</PackageVersion>
     <Title>TilesMath</Title>
     <Authors>ANYWAYS BV</Authors>
     <Description>A tiny library for tiles math.</Description>

test/TilesMath.Tests/Collections/TileTreeSetExtensionsTests.cs

@@ -0,0 +1,30 @@
+using TilesMath.Collections;
+
+namespace TilesMath.Tests.Collections;
+
+public class TileTreeSetExtensionsTests
+{
+    [Fact]
+    public void TileTreeSet_SetWithTileZero_CountAtZoom2_ShouldBe16()
+    {
+        var set = new TileTreeSet { Tile.Create(0, 0, 0) };
+
+        Assert.Equal(16, set.CountAtZoom(2));
+    }
+
+    [Fact]
+    public void TileTreeSet_SetWithTileZero_CountAtZoom14_ShouldBe268435456()
+    {
+        var set = new TileTreeSet { Tile.Create(0, 0, 0) };
+
+        Assert.Equal(268435456, set.CountAtZoom(14));
+    }
+
+    [Fact]
+    public void TileTreeSet_SetWithOneZoom14Tile_CountAtZoom14_ShouldBe1()
+    {
+        var set = new TileTreeSet { Tile.Create(0, 0, 14) };
+
+        Assert.Equal(1, set.CountAtZoom(14));
+    }
+}