sprite helper classes

tanks-backend/TanksServer/Graphics/DrawPowerUpsStep.cs

@@ -1,37 +1,14 @@
-using System.Diagnostics;
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
 using TanksServer.GameLogic;
 
 namespace TanksServer.Graphics;
 
-internal sealed class DrawPowerUpsStep : IDrawStep
+internal sealed class DrawPowerUpsStep(MapEntityManager entityManager) : IDrawStep
 {
-    private readonly MapEntityManager _entityManager;
+    private readonly Sprite _explosiveSprite = Sprite.FromImageFile("assets/powerup_explosive.png");
-    private readonly bool?[,] _explosiveSprite;
-
-    public DrawPowerUpsStep(MapEntityManager entityManager)
-    {
-        _entityManager = entityManager;
-
-        using var tankImage = Image.Load<Rgba32>("assets/powerup_explosive.png");
-        Debug.Assert(tankImage.Width == tankImage.Height && tankImage.Width == MapService.TileSize);
-        _explosiveSprite = new bool?[tankImage.Width, tankImage.Height];
-
-        var whitePixel = new Rgba32(byte.MaxValue, byte.MaxValue, byte.MaxValue, byte.MaxValue);
-        for (var y = 0; y < tankImage.Height; y++)
-        for (var x = 0; x < tankImage.Width; x++)
-        {
-            var pixelValue = tankImage[x, y];
-            _explosiveSprite[x, y] = pixelValue.A == 0
-                ? null
-                : pixelValue == whitePixel;
-        }
-    }
 
     public void Draw(GamePixelGrid pixels)
     {
-        foreach (var powerUp in _entityManager.PowerUps)
+        foreach (var powerUp in entityManager.PowerUps)
         {
             var position = powerUp.Bounds.TopLeft;
 

tanks-backend/TanksServer/Graphics/DrawTanksStep.cs

@@ -1,12 +1,11 @@
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
 using TanksServer.GameLogic;
 
 namespace TanksServer.Graphics;
 
 internal sealed class DrawTanksStep(MapEntityManager entityManager) : IDrawStep
 {
-    private readonly bool[,] _tankSprite = LoadTankSprite();
+    private readonly SpriteSheet _tankSprites =
+        SpriteSheet.FromImageFile("assets/tank.png", MapService.TileSize, MapService.TileSize);
 
     public void Draw(GamePixelGrid pixels)
     {
@@ -17,7 +16,8 @@ internal sealed class DrawTanksStep(MapEntityManager entityManager) : IDrawStep
             for (byte dy = 0; dy < MapService.TileSize; dy++)
             for (byte dx = 0; dx < MapService.TileSize; dx++)
             {
-                if (!TankSpriteAt(dx, dy, tank.Orientation))
+                var pixel = _tankSprites[tank.Orientation][dx, dy];
+                if (!pixel.HasValue || !pixel.Value)
                     continue;
 
                 var (x, y) = tankPosition.GetPixelRelative(dx, dy);
@@ -26,26 +26,4 @@ internal sealed class DrawTanksStep(MapEntityManager entityManager) : IDrawStep
             }
         }
     }
-
-    private bool TankSpriteAt(int dx, int dy, int tankRotation)
-    {
-        var x = tankRotation % 4 * (MapService.TileSize + 1);
-        var y = (int)Math.Floor(tankRotation / 4d) * (MapService.TileSize + 1);
-
-        return _tankSprite[x + dx, y + dy];
-    }
-
-    private static bool[,] LoadTankSprite()
-    {
-        using var tankImage = Image.Load<Rgba32>("assets/tank.png");
-        var tankSprite = new bool[tankImage.Width, tankImage.Height];
-
-        var whitePixel = new Rgba32(byte.MaxValue, byte.MaxValue, byte.MaxValue, byte.MaxValue);
-
-        for (var y = 0; y < tankImage.Height; y++)
-        for (var x = 0; x < tankImage.Width; x++)
-            tankSprite[x, y] = tankImage[x, y] == whitePixel;
-
-        return tankSprite;
-    }
 }

tanks-backend/TanksServer/Graphics/Sprite.cs

@@ -0,0 +1,27 @@
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace TanksServer.Graphics;
+
+internal sealed class Sprite(bool?[,] data)
+{
+    public static Sprite FromImageFile(string filePath)
+    {
+        using var image = Image.Load<Rgba32>(filePath);
+        var data = new bool?[image.Width, image.Height];
+
+        var whitePixel = new Rgba32(byte.MaxValue, byte.MaxValue, byte.MaxValue, byte.MaxValue);
+        for (var y = 0; y < image.Height; y++)
+        for (var x = 0; x < image.Width; x++)
+        {
+            var pixelValue = image[x, y];
+            data[x, y] = pixelValue.A == 0
+                ? null
+                : pixelValue == whitePixel;
+        }
+
+        return new Sprite(data);
+    }
+
+    public bool? this[int x, int y] => data[x, y];
+}

tanks-backend/TanksServer/Graphics/SpriteSheet.cs

@@ -0,0 +1,48 @@
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace TanksServer.Graphics;
+
+internal sealed class SpriteSheet(Sprite[,] sprites)
+{
+    public static SpriteSheet FromImageFile(string filePath, int spriteWidth, int spriteHeight)
+    {
+        using var image = Image.Load<Rgba32>(filePath);
+
+        var spritesPerRow = image.Width / spriteWidth;
+        if (image.Width % spriteWidth != 0)
+            throw new InvalidOperationException("invalid sprite dimensions");
+
+        var spritesPerColumn = image.Height / spriteHeight;
+        if (image.Height % spriteHeight != 0)
+            throw new InvalidOperationException("invalid sprite dimensions");
+
+        var sprites = new Sprite[spritesPerRow, spritesPerColumn];
+
+        var whitePixel = new Rgba32(byte.MaxValue, byte.MaxValue, byte.MaxValue, byte.MaxValue);
+        for (var spriteY = 0; spriteY < spritesPerColumn; spriteY++)
+        for (var spriteX = 0; spriteX < spritesPerRow; spriteX++)
+        {
+            var data = new bool?[spriteWidth, spriteHeight];
+            for (var dy = 0; dy < spriteHeight; dy++)
+            for (var dx = 0; dx < spriteWidth; dx++)
+            {
+                var x = spriteX * spriteWidth + dx;
+                var y = spriteY * spriteHeight + dy;
+
+                var pixelValue = image[x, y];
+                data[dx, dy] = pixelValue.A == 0
+                    ? null
+                    : pixelValue == whitePixel;
+            }
+
+            sprites[spriteX, spriteY] = new Sprite(data);
+        }
+
+        return new SpriteSheet(sprites);
+    }
+
+    public Sprite this[int x, int y] => sprites[x, y];
+
+    public Sprite this[int index] => sprites[index % sprites.GetLength(1), index / sprites.GetLength(1)];
+}