From 3f238c619eb1e8afbe0da3ecd2eb9fd524d1d8b0 Mon Sep 17 00:00:00 2001
From: jracek <racek.janek@gmail.com>
Date: Tue, 14 Jan 2025 20:47:01 +0100
Subject: [PATCH] Added dithering option to textures

---
 Editor/QuantizedPreviewWindow.cs |  9 +++++-
 Runtime/PSXTexture.cs            | 53 ++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 1 deletion(-)

diff --git a/Editor/QuantizedPreviewWindow.cs b/Editor/QuantizedPreviewWindow.cs
index 1d56d23..fc7589b 100644
--- a/Editor/QuantizedPreviewWindow.cs
+++ b/Editor/QuantizedPreviewWindow.cs
@@ -14,8 +14,9 @@ public class QuantizedPreviewWindow : EditorWindow
     private int bpp = 4;
     private int targetWidth = 128;
     private int targetHeight = 128;
+    public bool dithering = true;
     private int maxKMeans = 100;
-    private int previewSize = 256;
+    private readonly int previewSize = 256;
 
     [MenuItem("Window/Quantized Preview")]
     public static void ShowWindow()
@@ -33,6 +34,8 @@ public class QuantizedPreviewWindow : EditorWindow
         targetWidth = EditorGUILayout.IntField("Target Width", targetWidth);
         targetHeight = EditorGUILayout.IntField("Target Height", targetHeight);
 
+        dithering = EditorGUILayout.Toggle("Dithering", dithering);
+
         bpp = EditorGUILayout.IntPopup("Bits Per Pixel", bpp, new[] { "4 bpp", "8 bpp", "16 bpp" }, new[] { 4, 8, 16 });
         maxKMeans = EditorGUILayout.IntField("Max K-Means", maxKMeans);
 
@@ -132,6 +135,10 @@ public class QuantizedPreviewWindow : EditorWindow
     {
         Texture2D resizedTexture = PSXTexture.ResizeTexture(originalTexture, targetWidth, targetHeight);
 
+        if(dithering) {
+            resizedTexture = PSXTexture.DitherTexture(resizedTexture);
+        }
+
         if (bpp == 16)
         {
             quantizedTexture = null;
diff --git a/Runtime/PSXTexture.cs b/Runtime/PSXTexture.cs
index e126cf9..cd99f14 100644
--- a/Runtime/PSXTexture.cs
+++ b/Runtime/PSXTexture.cs
@@ -44,6 +44,10 @@ namespace PSXSplash.RuntimeCode
                     Texture2D originalTexture = (Texture2D)texture;
 
                     Texture2D newTexture = ResizeTexture(originalTexture, Width, Height);
+                    if (Dithering)
+                    {
+                        newTexture = DitherTexture(newTexture);
+                    }
                     if (TextureType == PSXTextureType.TEX16_BPP)
                     {
                         ushort[] converted = ConvertTo16Bpp(newTexture);
@@ -138,6 +142,55 @@ namespace PSXSplash.RuntimeCode
             return packedData;
         }
 
+        public static Texture2D DitherTexture(Texture2D sourceTexture, float threshold = 0.2f, float errorDiffusionStrength = 0.1f)
+        {
+            int width = sourceTexture.width;
+            int height = sourceTexture.height;
+            Color[] pixels = sourceTexture.GetPixels();
+            Color[] ditheredPixels = new Color[pixels.Length];
+
+            for (int y = 0; y < height; y++)
+            {
+                for (int x = 0; x < width; x++)
+                {
+                    int index = y * width + x;
+                    Color pixel = pixels[index];
+
+                    // Convert the pixel to grayscale
+                    float gray = pixel.grayscale;
+
+                    // Apply threshold to determine if it's black or white
+                    int dithered = (gray > threshold) ? 1 : 0;
+
+                    // Calculate the error as the difference between the grayscale value and the dithered result
+                    float error = gray - dithered;
+
+                    // Store the dithered pixel
+                    ditheredPixels[index] = new Color(dithered, dithered, dithered);
+
+                    // Spread the error to neighboring pixels with customizable error diffusion strength
+                    if (x + 1 < width) pixels[(y * width) + (x + 1)] += new Color(error * 7f / 16f * errorDiffusionStrength, error * 7f / 16f * errorDiffusionStrength, error * 7f / 16f * errorDiffusionStrength);
+                    if (y + 1 < height) pixels[((y + 1) * width) + x] += new Color(error * 3f / 16f * errorDiffusionStrength, error * 3f / 16f * errorDiffusionStrength, error * 3f / 16f * errorDiffusionStrength);
+                    if (x - 1 >= 0 && y + 1 < height) pixels[((y + 1) * width) + (x - 1)] += new Color(error * 5f / 16f * errorDiffusionStrength, error * 5f / 16f * errorDiffusionStrength, error * 5f / 16f * errorDiffusionStrength);
+                    if (x + 1 < width && y + 1 < height) pixels[((y + 1) * width) + (x + 1)] += new Color(error * 1f / 16f * errorDiffusionStrength, error * 1f / 16f * errorDiffusionStrength, error * 1f / 16f * errorDiffusionStrength);
+                }
+            }
+
+            // Clamp the final pixel values to ensure they are valid colors
+            for (int i = 0; i < pixels.Length; i++)
+            {
+                pixels[i].r = Mathf.Clamp01(pixels[i].r);
+                pixels[i].g = Mathf.Clamp01(pixels[i].g);
+                pixels[i].b = Mathf.Clamp01(pixels[i].b);
+            }
+
+            // Create the resulting dithered texture
+            Texture2D ditheredTexture = new Texture2D(width, height);
+            ditheredTexture.SetPixels(pixels);
+            ditheredTexture.Apply();
+
+            return ditheredTexture;
+        }
 
     }
 }