From c01001fddb1eee22d316ce8648db295a37a7f26c Mon Sep 17 00:00:00 2001
From: Brian Popow <popow@gmx.de>
Date: Wed, 23 Feb 2022 20:07:09 +0100
Subject: [PATCH] Add comment about pixel layout

---
 src/ImageSharp/Formats/Png/Filters/AverageFilter.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs b/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs
index 7747d14ea2..a99b93adb5 100644
--- a/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs
+++ b/src/ImageSharp/Formats/Png/Filters/AverageFilter.cs
@@ -32,6 +32,9 @@ namespace SixLabors.ImageSharp.Formats.Png.Filters
 
             // The Avg filter predicts each pixel as the (truncated) average of a and b:
             // Average(x) + floor((Raw(x-bpp)+Prior(x))/2)
+            // With pixels positioned like this:
+            //  prev:  c b
+            //  row:   a d
 #if SUPPORTS_RUNTIME_INTRINSICS
             if (Sse2.IsSupported && bytesPerPixel is 4)
             {