Add comment about pixel layout

4 years ago · c01001fddb
1 changed files with 3 additions and 0 deletions
--- 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)
            {