Update

Author: evgeniy-polyakov

ArcanumTextureSlicer/ArcanumTextureSlicer/ArcanumTextureSlicer.csproj

@@ -51,6 +51,9 @@
   <ItemGroup>
     <None Include="App.config" />
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Resources\SampleTile.png" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.

ArcanumTextureSlicer/ArcanumTextureSlicer/BitmapExtensions.cs

@@ -1,20 +1,37 @@
 using System;
 using System.Drawing;
 using System.Drawing.Imaging;
+using System.Reflection;
 using System.Runtime.InteropServices;
 
 namespace ArcanumTextureSlicer
 {
     public static class BitmapExtensions
     {
+        private static Bitmap _sampleTile;
+
+        public static readonly Color AlphaColor = Color.Blue;
+
+        public static Bitmap SampleTile =>
+            _sampleTile ??
+            (_sampleTile = new Bitmap(Assembly.GetExecutingAssembly()
+                .GetManifestResourceStream("ArcanumTextureSlicer.Resources.SampleTile.png")));
+
+        public static Bitmap CreateTile(this Bitmap source, int x, int y)
+        {
+            var tile = CloneRegion(source, new Rectangle(x, y, SampleTile.Width, SampleTile.Height));
+            tile.DrawAlpha(SampleTile);
+            return tile;
+        }
+
         public static Bitmap CloneRegion(this Bitmap source, Rectangle rect)
         {
             if (rect.X >= 0 && rect.Y >= 0 && rect.Right <= source.Width && rect.Bottom <= source.Height)
             {
                 return source.Clone(rect, source.PixelFormat);
             }
             var bitmap = source.Clone(new Rectangle(0, 0, rect.Width, rect.Height), source.PixelFormat);
-            bitmap.SetColor(Color.Blue);
+            bitmap.SetColor(AlphaColor);
             bitmap.DrawImage(source,
                 Math.Max(-rect.X, 0),
                 Math.Max(-rect.Y, 0),
@@ -38,6 +55,42 @@ public static void SetColor(this Bitmap canvas, Color color)
             canvas.UnlockBits(data);
         }
 
+        public static void DrawAlpha(this Bitmap canvas, Bitmap sample)
+        {
+            var rect = new Rectangle(0, 0, canvas.Width, canvas.Height);
+
+            var sampleData = sample.LockBits(rect, ImageLockMode.ReadOnly, sample.PixelFormat);
+            var canvasData = canvas.LockBits(rect, ImageLockMode.WriteOnly, canvas.PixelFormat);
+            try
+            {
+                var sampleAlphaIndex = sample.GetColorIndex(AlphaColor);
+                var canvasAlphaIndex = canvas.GetColorIndex(AlphaColor);
+
+                var sampleBytes = new byte[sampleData.Height*sampleData.Stride];
+                var canvasBytes = new byte[canvasData.Height*canvasData.Stride];
+                Marshal.Copy(sampleData.Scan0, sampleBytes, 0, sampleBytes.Length);
+                Marshal.Copy(canvasData.Scan0, canvasBytes, 0, canvasBytes.Length);
+
+                for (var y = 0; y < canvasData.Height; y++)
+                {
+                    for (var x = 0; x < canvasData.Width; x++)
+                    {
+                        if (sampleBytes[x + y*sampleData.Stride] == sampleAlphaIndex)
+                        {
+                            canvasBytes[x + y*canvasData.Stride] = canvasAlphaIndex;
+                        }
+                    }
+                }
+
+                Marshal.Copy(canvasBytes, 0, canvasData.Scan0, canvasBytes.Length);
+            }
+            finally
+            {
+                sample.UnlockBits(sampleData);
+                canvas.UnlockBits(canvasData);
+            }
+        }
+
         public static void DrawImage(this Bitmap canvas, Bitmap source, int canvasX, int canvasY, Rectangle sourceRect)
         {
             var sourceData = source.LockBits(sourceRect, ImageLockMode.ReadOnly, source.PixelFormat);

ArcanumTextureSlicer/ArcanumTextureSlicer/Program.cs

@@ -18,10 +18,10 @@ public static void Main(string[] args)
             var inputFile = args[0];
             var outputFolder = args[1];
 
-            const int tileWidth = 78;
-            const int tileHeight = 40;
-            const int halfTileWidth = 39;
-            const int halfTileHeight = 20;
+            var tileWidth = BitmapExtensions.SampleTile.Width;
+            var tileHeight = BitmapExtensions.SampleTile.Height;
+            var halfTileWidth = tileWidth/2;
+            var halfTileHeight = tileHeight/2;
 
             try
             {
@@ -33,10 +33,9 @@ public static void Main(string[] args)
                     {
                         for (var j = 0; j < m; j++)
                         {
-                            using (var outputBitmap = inputBitmap.CloneRegion(new Rectangle(
+                            using (var outputBitmap = inputBitmap.CreateTile(
                                 i*tileWidth - halfTileWidth*(1 - j%2),
-                                j*tileHeight/2,
-                                tileWidth, tileHeight)))
+                                j*halfTileHeight - halfTileHeight))
                             {
                                 try
                                 {