From 6d9a04d38cec01db10ff9197a92489adbe33ad81 Mon Sep 17 00:00:00 2001
From: Anton Firszov <antonfir@gmail.com>
Date: Tue, 5 Oct 2021 14:27:27 +0200
Subject: [PATCH] Premultiply only if alpha representation is unknown or
 Unassociated

---
 .../Transforms/Resize/ResizeProcessor{TPixel}.cs           | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor{TPixel}.cs b/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor{TPixel}.cs
index 1daed9ee63..c5e53318d2 100644
--- a/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor{TPixel}.cs
+++ b/src/ImageSharp/Processing/Processors/Transforms/Resize/ResizeProcessor{TPixel}.cs
@@ -188,8 +188,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
             bool compand,
             bool premultiplyAlpha)
         {
-            bool pixelHasNoAlpha = PixelOperations<TPixel>.Instance.GetPixelTypeInfo()?.AlphaRepresentation == PixelAlphaRepresentation.None;
-            premultiplyAlpha &= !pixelHasNoAlpha;
+            PixelAlphaRepresentation? alphaRepresentation = PixelOperations<TPixel>.Instance.GetPixelTypeInfo()?.PixelAlphaRepresentation;
+
+            // Premultiply only if alpha representation is unknown or Unassociated:
+            bool needsPremultiplication = alphaRepresentation == null || alphaRepresentation.Value == PixelAlphaRepresentation.Unassociated;
+            premultiplyAlpha &= needsPremultiplication;
             PixelConversionModifiers conversionModifiers = GetModifiers(compand, premultiplyAlpha);
 
             Buffer2DRegion<TPixel> sourceRegion = source.PixelBuffer.GetRegion(sourceRectangle);