From 396cd8d2cb3c7f325518075cb6d2101301ec1562 Mon Sep 17 00:00:00 2001
From: winscripter <142818255+winscripter@users.noreply.github.com>
Date: Thu, 16 Jul 2026 13:53:33 +0400
Subject: [PATCH] Implement JxlAnsHelper.GetPopulationCountPrecision

See ans_common.h
---
 src/ImageSharp/Formats/Jxl/IO/JxlAnsHelper.cs | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100644 src/ImageSharp/Formats/Jxl/IO/JxlAnsHelper.cs

diff --git a/src/ImageSharp/Formats/Jxl/IO/JxlAnsHelper.cs b/src/ImageSharp/Formats/Jxl/IO/JxlAnsHelper.cs
new file mode 100644
index 0000000000..babbfe8fd5
--- /dev/null
+++ b/src/ImageSharp/Formats/Jxl/IO/JxlAnsHelper.cs
@@ -0,0 +1,25 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Buffers;
+using System.Diagnostics;
+using System.Runtime.CompilerServices;
+using static SixLabors.ImageSharp.Formats.Jxl.IO.JxlAnsConstants;
+
+namespace SixLabors.ImageSharp.Formats.Jxl.IO;
+
+internal static class JxlAnsHelper
+{
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static int GetPopulationCountPrecision(int logCount, int shift)
+    {
+        int r = Math.Min(logCount, shift - ((AnsLogTableSize - logCount) >> 1));
+
+        if (r < 0)
+        {
+            return 0;
+        }
+
+        return r;
+    }
+}