From 57eadbb3f94ced32b2500a1c2bfd45463b90d1d3 Mon Sep 17 00:00:00 2001
From: winscripter <142818255+winscripter@users.noreply.github.com>
Date: Fri, 17 Jul 2026 00:51:42 +0400
Subject: [PATCH] Implement noise shared logic

---
 .../Formats/Jxl/Processing/JxlNoiseHelper.cs  | 28 +++++++++++++++++++
 .../Processing/JxlNoiseIndexAndFraction.cs    | 14 ++++++++++
 .../Formats/Jxl/Processing/JxlNoiseLevel.cs   | 14 ++++++++++
 .../Jxl/Processing/JxlNoiseParameters.cs      | 15 ++++++++++
 4 files changed, 71 insertions(+)
 create mode 100644 src/ImageSharp/Formats/Jxl/Processing/JxlNoiseHelper.cs
 create mode 100644 src/ImageSharp/Formats/Jxl/Processing/JxlNoiseIndexAndFraction.cs
 create mode 100644 src/ImageSharp/Formats/Jxl/Processing/JxlNoiseLevel.cs
 create mode 100644 src/ImageSharp/Formats/Jxl/Processing/JxlNoiseParameters.cs

diff --git a/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseHelper.cs b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseHelper.cs
new file mode 100644
index 0000000000..f6432e24db
--- /dev/null
+++ b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseHelper.cs
@@ -0,0 +1,28 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+
+namespace SixLabors.ImageSharp.Formats.Jxl.Processing;
+
+internal static class JxlNoiseHelper
+{
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static JxlNoiseIndexAndFraction IndexAndFraction(float x)
+    {
+        const int scaleNumerator = JxlNoiseParameters.NoisePoints - 2;
+        const float scale = scaleNumerator / 1.0f;
+
+        float scaledX = MathF.Max(0f, x * scale);
+        float floorX = MathF.Floor(scaledX);
+        float fractionalX = scaledX - floorX;
+
+        if (scaledX >= scaleNumerator + 1)
+        {
+            floorX = scaleNumerator;
+            fractionalX = 1f;
+        }
+
+        return new((int)floorX, fractionalX);
+    }
+}
diff --git a/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseIndexAndFraction.cs b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseIndexAndFraction.cs
new file mode 100644
index 0000000000..c3ec1437c8
--- /dev/null
+++ b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseIndexAndFraction.cs
@@ -0,0 +1,14 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.InteropServices;
+
+namespace SixLabors.ImageSharp.Formats.Jxl.Processing;
+
+[StructLayout(LayoutKind.Sequential)]
+internal struct JxlNoiseIndexAndFraction(int index, float fraction)
+{
+    public int Index = index;
+
+    public float Fraction = fraction;
+}
diff --git a/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseLevel.cs b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseLevel.cs
new file mode 100644
index 0000000000..d5feebd52b
--- /dev/null
+++ b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseLevel.cs
@@ -0,0 +1,14 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.InteropServices;
+
+namespace SixLabors.ImageSharp.Formats.Jxl.Processing;
+
+[StructLayout(LayoutKind.Sequential)]
+internal struct JxlNoiseLevel(float noiseLevel, float intensity)
+{
+    public float NoiseLevel = noiseLevel;
+
+    public float Intensity = intensity;
+}
diff --git a/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseParameters.cs b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseParameters.cs
new file mode 100644
index 0000000000..3f51f85379
--- /dev/null
+++ b/src/ImageSharp/Formats/Jxl/Processing/JxlNoiseParameters.cs
@@ -0,0 +1,15 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Jxl.Processing;
+
+internal sealed class JxlNoiseParameters
+{
+    public const int NoisePoints = 8;
+
+    public float[] Lookup { get; set; } = new float[NoisePoints];
+
+    public bool ContainsAny => this.Lookup.Any(x => MathF.Abs(x) > 1e-3f);
+
+    public void Clear() => Array.Fill(this.Lookup, 0f);
+}