sprite helper classes

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)];
+}