Fix ResizeProcessor Compand UnPremultiply bug + tests

src/ImageSharp/Common/Helpers/ImageMaths.cs

@@ -2,9 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
-using System.Numerics;
 using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
 
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.Primitives;
@@ -33,6 +31,7 @@ namespace SixLabors.ImageSharp
 
         /// <summary>
         /// Determine the Least Common Multiple (LCM) of two numbers.
+        /// TODO: This method might be useful for building a more compact <see cref="Processing.Processors.Transforms.KernelMap"/>
         /// </summary>
         public static int LeastCommonMultiple(int a, int b)
         {

src/ImageSharp/Processing/Processors/Transforms/ResizeProcessor.cs

@@ -263,7 +263,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Transforms
                                         ResizeKernel window = this.horizontalKernelMap.Kernels[x - startX];
 
                                         Unsafe.Add(ref firstPassBaseRef, x * sourceHeight) =
-                                            window.ConvolveExpand(tempRowSpan, sourceX).UnPremultiply();
+                                            window.ConvolveExpand(tempRowSpan, sourceX);
                                     }
                                 }
                                 else

tests/ImageSharp.Tests/Processing/Processors/Transforms/ResizeTests.cs

@@ -18,8 +18,8 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
     {
         public static readonly string[] CommonTestImages = { TestImages.Png.CalliphoraPartial };
 
-        private static readonly ImageComparer ValidatorComparer = ImageComparer.TolerantPercentage(0.069F);
+        private static readonly ImageComparer ValidatorComparer = ImageComparer.TolerantPercentage(0.07F);
-
+        
         public static readonly TheoryData<string, IResampler> AllReSamplers =
             new TheoryData<string, IResampler>
             {
@@ -65,20 +65,16 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
         public void Resize_WorksWithAllParallelismLevels<TPixel>(TestImageProvider<TPixel> provider, int maxDegreeOfParallelism)
             where TPixel : struct, IPixel<TPixel>
         {
-            if (maxDegreeOfParallelism >= 0)
+            provider.Configuration.MaxDegreeOfParallelism =
-            {
+                maxDegreeOfParallelism > 0 ? maxDegreeOfParallelism : Environment.ProcessorCount;
-                provider.Configuration.MaxDegreeOfParallelism = maxDegreeOfParallelism;
-            }
 
-            using (Image<TPixel> image = provider.GetImage())
+            FormattableString details = $"MDP{maxDegreeOfParallelism}";
-            {
-                SizeF newSize = image.Size() * 0.5f;
-                image.Mutate(x => x.Resize((Size)newSize, false));
-                FormattableString details = $"MDP{maxDegreeOfParallelism}";
 
-                image.DebugSave(provider, details);
+            provider.RunValidatingProcessorTest(
-                //image.CompareToReferenceOutput(ImageComparer.TolerantPercentage(0.005f), provider, details);
+                x => x.Resize(x.GetCurrentSize() / 2),
-            }
+                details,
+                appendPixelTypeToFileName: false,
+                appendSourceFileOrDescription: false);
         }
 
         [Theory]
@@ -100,16 +96,9 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
         public void Resize_IsNotBoundToSinglePixelType<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
+            provider.RunValidatingProcessorTest(x => x.Resize(x.GetCurrentSize() / 2), comparer: ValidatorComparer);
-            {
-                image.Mutate(x => x.Resize(image.Width / 2, image.Height / 2, true));
-
-                image.DebugSave(provider);
-                image.CompareToReferenceOutput(ValidatorComparer, provider);
-            }
         }
 
-
         [Theory]
         [WithFileCollection(nameof(CommonTestImages), DefaultPixelType)]
         public void Resize_ThrowsForWrappedMemoryImage<TPixel>(TestImageProvider<TPixel> provider)
@@ -130,32 +119,21 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Transforms
             }
         }
 
-
         [Theory]
-        [WithFile(TestImages.Png.Kaboom, DefaultPixelType)]
+        [WithFile(TestImages.Png.Kaboom, DefaultPixelType, false)]
-        public void Resize_DoesNotBleedAlphaPixels<TPixel>(TestImageProvider<TPixel> provider)
+        [WithFile(TestImages.Png.Kaboom, DefaultPixelType, true)]
+        public void Resize_DoesNotBleedAlphaPixels<TPixel>(TestImageProvider<TPixel> provider, bool compand)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
+            string details = compand ? "Compand" : "";
-            {
-                image.Mutate(x => x.Resize(image.Width / 2, image.Height / 2));
-                image.DebugSave(provider);
-                image.CompareToReferenceOutput(ValidatorComparer, provider);
-            }
-        }
 
-        [Theory]
+            provider.RunValidatingProcessorTest(
-        [WithFile(TestImages.Png.Kaboom, DefaultPixelType)]
+                x => x.Resize(x.GetCurrentSize() / 2, compand),
-        public void Resize_Compand_DoesNotBleedAlphaPixels<TPixel>(TestImageProvider<TPixel> provider)
+                details,
-            where TPixel : struct, IPixel<TPixel>
+                appendPixelTypeToFileName: false,
-        {
+                appendSourceFileOrDescription: false);
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Resize(image.Width / 2, image.Height / 2, true));
-                image.DebugSave(provider);
-            }
         }
-
+        
         [Theory]
         [WithFile(TestImages.Gif.Giphy, DefaultPixelType)]
         public void Resize_IsAppliedToAllFrames<TPixel>(TestImageProvider<TPixel> provider)

tests/Images/External

@@ -1 +1 @@
-Subproject commit c0627f384c1d3d2f8d914c9578ae31354c35fd2c
+Subproject commit 03c7fa7582dea75cea0d49514ccb7e1b6dc9e780