From 84852a879681034fe7d3dcdba76e9cd7dba52ca7 Mon Sep 17 00:00:00 2001
From: Anton Firszov <anton.firszov@sapagroup.com>
Date: Fri, 18 Aug 2017 16:45:10 +0200
Subject: [PATCH 1/4] good by GenericFactory!

---
 .../Formats/Jpg/JpegDecoderTests.cs           |  4 +--
 .../Formats/Jpg/JpegUtilsTests.cs             | 12 +++----
 .../Image/PixelAccessorTests.cs               |  8 ++---
 .../ImageSharp.Tests/ImageSharp.Tests.csproj  |  3 ++
 .../Attributes/WithMemberFactoryAttribute.cs  |  3 +-
 .../TestUtilities/Factories/GenericFactory.cs | 36 -------------------
 .../TestUtilities/Factories/ImageFactory.cs   | 24 -------------
 .../ImageComparison/ImageSimilarityReport.cs  |  2 +-
 .../ImageProviders/BlankProvider.cs           |  2 +-
 .../ImageProviders/LambdaProvider.cs          |  8 ++---
 .../ImageProviders/TestImageProvider.cs       | 12 ++-----
 .../Tests/TestImageProviderTests.cs           |  4 +--
 .../Tests/TestUtilityExtensionsTests.cs       |  8 ++---
 13 files changed, 31 insertions(+), 95 deletions(-)
 delete mode 100644 tests/ImageSharp.Tests/TestUtilities/Factories/GenericFactory.cs
 delete mode 100644 tests/ImageSharp.Tests/TestUtilities/Factories/ImageFactory.cs

diff --git a/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs b/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs
index 141105c487..682b457c88 100644
--- a/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Jpg/JpegDecoderTests.cs
@@ -76,8 +76,8 @@ namespace ImageSharp.Tests
                     image.Save(ms, encoder);
                 }
             }
-            
-            Image<TPixel> mirror = provider.Factory.CreateImage(data);
+
+            Image<TPixel> mirror = Image.Load<TPixel>(data);
             mirror.DebugSave(provider, $"_{subsample}_Q{quality}");
         }
 
diff --git a/tests/ImageSharp.Tests/Formats/Jpg/JpegUtilsTests.cs b/tests/ImageSharp.Tests/Formats/Jpg/JpegUtilsTests.cs
index f681e1d8f9..1075c46921 100644
--- a/tests/ImageSharp.Tests/Formats/Jpg/JpegUtilsTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Jpg/JpegUtilsTests.cs
@@ -16,19 +16,19 @@ namespace ImageSharp.Tests
 
     public class JpegUtilsTests : TestBase
     {
-        public static Image<TPixel> CreateTestImage<TPixel>(GenericFactory<TPixel> factory)
+        public static Image<TPixel> CreateTestImage<TPixel>()
             where TPixel : struct, IPixel<TPixel>
         {
-            Image<TPixel> image = factory.CreateImage(10, 10);
+            var image = new Image<TPixel>(10, 10);
             using (PixelAccessor<TPixel> pixels = image.Lock())
             {
                 for (int i = 0; i < 10; i++)
                 {
                     for (int j = 0; j < 10; j++)
                     {
-                        Vector4 v = new Vector4(i / 10f, j / 10f, 0, 1);
+                        var v = new Vector4(i / 10f, j / 10f, 0, 1);
 
-                        TPixel color = default(TPixel);
+                        var color = default(TPixel);
                         color.PackFromVector4(v);
 
                         pixels[i, j] = color;
@@ -45,7 +45,7 @@ namespace ImageSharp.Tests
             where TPixel : struct, IPixel<TPixel>
         {
             using (Image<TPixel> src = provider.GetImage())
-            using (Image<TPixel> dest = provider.Factory.CreateImage(8, 8))
+            using (Image<TPixel> dest = new Image<TPixel>(8,8))
             using (PixelArea<TPixel> area = new PixelArea<TPixel>(8, 8, ComponentOrder.Xyz))
             using (PixelAccessor<TPixel> s = src.Lock())
             using (PixelAccessor<TPixel> d = dest.Lock())
@@ -68,7 +68,7 @@ namespace ImageSharp.Tests
         {
             using (Image<TPixel> src = provider.GetImage())
             using (PixelArea<TPixel> area = new PixelArea<TPixel>(8, 8, ComponentOrder.Xyz))
-            using (Image<TPixel> dest = provider.Factory.CreateImage(8, 8))
+            using (Image<TPixel> dest = new Image<TPixel>(8, 8))
             using (PixelAccessor<TPixel> s = src.Lock())
             using (PixelAccessor<TPixel> d = dest.Lock())
             {
diff --git a/tests/ImageSharp.Tests/Image/PixelAccessorTests.cs b/tests/ImageSharp.Tests/Image/PixelAccessorTests.cs
index 98f316f439..37333576b5 100644
--- a/tests/ImageSharp.Tests/Image/PixelAccessorTests.cs
+++ b/tests/ImageSharp.Tests/Image/PixelAccessorTests.cs
@@ -17,20 +17,20 @@ namespace ImageSharp.Tests
     /// </summary>
     public class PixelAccessorTests
     {
-        public static Image<TPixel> CreateTestImage<TPixel>(GenericFactory<TPixel> factory)
+        public static Image<TPixel> CreateTestImage<TPixel>()
             where TPixel : struct, IPixel<TPixel>
         {
-            Image<TPixel> image = factory.CreateImage(10, 10);
+            var image = new Image<TPixel>(10, 10);
             using (PixelAccessor<TPixel> pixels = image.Lock())
             {
                 for (int i = 0; i < 10; i++)
                 {
                     for (int j = 0; j < 10; j++)
                     {
-                        Vector4 v = new Vector4(i, j, 0, 1);
+                        var v = new Vector4(i, j, 0, 1);
                         v /= 10;
 
-                        TPixel color = default(TPixel);
+                        var color = default(TPixel);
                         color.PackFromVector4(v);
 
                         pixels[i, j] = color;
diff --git a/tests/ImageSharp.Tests/ImageSharp.Tests.csproj b/tests/ImageSharp.Tests/ImageSharp.Tests.csproj
index 491b245bc4..03805ae32a 100644
--- a/tests/ImageSharp.Tests/ImageSharp.Tests.csproj
+++ b/tests/ImageSharp.Tests/ImageSharp.Tests.csproj
@@ -28,4 +28,7 @@
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </None>
   </ItemGroup>
+  <ItemGroup>
+    <Folder Include="TestUtilities\Factories\" />
+  </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/Attributes/WithMemberFactoryAttribute.cs b/tests/ImageSharp.Tests/TestUtilities/Attributes/WithMemberFactoryAttribute.cs
index 6c6198c38d..53faff640a 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Attributes/WithMemberFactoryAttribute.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Attributes/WithMemberFactoryAttribute.cs
@@ -39,9 +39,8 @@ namespace ImageSharp.Tests
             Type colorType = args.Single();
 
             Type imgType = typeof(Image<>).MakeGenericType(colorType);
-            Type genericFactoryType = (typeof(GenericFactory<>)).MakeGenericType(colorType);
 
-            Type funcType = typeof(Func<,>).MakeGenericType(genericFactoryType, imgType);
+            Type funcType = typeof(Func<>).MakeGenericType(imgType);
 
             MethodInfo genericMethod = m.MakeGenericMethod(args);
 
diff --git a/tests/ImageSharp.Tests/TestUtilities/Factories/GenericFactory.cs b/tests/ImageSharp.Tests/TestUtilities/Factories/GenericFactory.cs
deleted file mode 100644
index efe548ee88..0000000000
--- a/tests/ImageSharp.Tests/TestUtilities/Factories/GenericFactory.cs
+++ /dev/null
@@ -1,36 +0,0 @@
-// <copyright file="GenericFactory.cs" company="James Jackson-South">
-// Copyright (c) James Jackson-South and contributors.
-// Licensed under the Apache License, Version 2.0.
-// </copyright>
-
-namespace ImageSharp.Tests
-{
-    using System;
-
-    using ImageSharp.PixelFormats;
-
-    /// <summary>
-    /// TODO: Non-generic 'Image' class has been removed. We no longer need the factory pattern here!
-    /// 
-    /// Utility class to create specialized subclasses of generic classes (eg. <see cref="Image"/>)
-    /// Used as parameter for <see cref="WithMemberFactoryAttribute"/> -based factory methods
-    /// </summary>
-    public class GenericFactory<TPixel>
-        where TPixel : struct, IPixel<TPixel>
-    {
-        public virtual Image<TPixel> CreateImage(int width, int height)
-        {
-            return new Image<TPixel>(width, height);
-        }
-
-        public virtual Image<TPixel> CreateImage(byte[] bytes)
-        {
-            return Image.Load<TPixel>(bytes);
-        }
-
-        public virtual Image<TPixel> CreateImage(Image<TPixel> other)
-        {
-            return other.Clone();
-        }
-    }
-}
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/Factories/ImageFactory.cs b/tests/ImageSharp.Tests/TestUtilities/Factories/ImageFactory.cs
deleted file mode 100644
index efa08c736f..0000000000
--- a/tests/ImageSharp.Tests/TestUtilities/Factories/ImageFactory.cs
+++ /dev/null
@@ -1,24 +0,0 @@
-// <copyright file="ImageFactory.cs" company="James Jackson-South">
-// Copyright (c) James Jackson-South and contributors.
-// Licensed under the Apache License, Version 2.0.
-// </copyright>
-
-namespace ImageSharp.Tests
-{
-    using ImageSharp.PixelFormats;
-
-    /// <summary>
-    /// TODO: Non-generic 'Image' class has been removed. We no longer need the factory pattern here!
-    /// </summary>
-    public class ImageFactory : GenericFactory<Rgba32>
-    {
-        public override Image<Rgba32> CreateImage(byte[] bytes) => Image.Load<Rgba32>(bytes);
-
-        public override Image<Rgba32> CreateImage(int width, int height) => new Image<Rgba32>(width, height);
-
-        public override Image<Rgba32> CreateImage(Image<Rgba32> other)
-        {
-            return other.Clone();
-        }
-    }
-}
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageSimilarityReport.cs b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageSimilarityReport.cs
index 74995537e6..313d7ffb87 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageSimilarityReport.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageSimilarityReport.cs
@@ -42,7 +42,7 @@
             var sb = new StringBuilder();
             if (this.TotalNormalizedDifference.HasValue)
             {
-                sb.AppendLine($"Total difference: {this.TotalNormalizedDifference.Value * 100:0.00}%");
+                sb.AppendLine($"Total difference: {this.TotalNormalizedDifference.Value * 100:0.0000}%");
             }
             int max = Math.Min(5, this.Differences.Length);
 
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
index 4252a60b5e..af5e838755 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/BlankProvider.cs
@@ -33,7 +33,7 @@ namespace ImageSharp.Tests
 
             protected int Width { get; private set; }
 
-            public override Image<TPixel> GetImage() => this.Factory.CreateImage(this.Width, this.Height);
+            public override Image<TPixel> GetImage() => new Image<TPixel>(this.Width, this.Height);
 
 
             public override void Deserialize(IXunitSerializationInfo info)
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/LambdaProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/LambdaProvider.cs
index 30e7a63b50..ee150adc7c 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/LambdaProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/LambdaProvider.cs
@@ -18,14 +18,14 @@ namespace ImageSharp.Tests
     {
         private class LambdaProvider : TestImageProvider<TPixel>
         {
-            private readonly Func<GenericFactory<TPixel>, Image<TPixel>> creator;
+            private readonly Func<Image<TPixel>> factoryFunc;
 
-            public LambdaProvider(Func<GenericFactory<TPixel>, Image<TPixel>> creator)
+            public LambdaProvider(Func<Image<TPixel>> factoryFunc)
             {
-                this.creator = creator;
+                this.factoryFunc = factoryFunc;
             }
 
-            public override Image<TPixel> GetImage() => this.creator(this.Factory);
+            public override Image<TPixel> GetImage() => this.factoryFunc();
         }
     }
 }
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs
index 99d1125d72..cc8c453c80 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/TestImageProvider.cs
@@ -33,7 +33,6 @@ namespace ImageSharp.Tests
         /// </summary>
         public ImagingTestCaseUtility Utility { get; private set; }
 
-        public GenericFactory<TPixel> Factory { get; private set; } = new GenericFactory<TPixel>();
         public string TypeName { get; private set; }
         public string MethodName { get; private set; }
 
@@ -60,10 +59,10 @@ namespace ImageSharp.Tests
         }
 
         public static TestImageProvider<TPixel> Lambda(
-                Func<GenericFactory<TPixel>, Image<TPixel>> func,
+                Func<Image<TPixel>> factoryFunc,
                 MethodInfo testMethod = null,
                 PixelTypes pixelTypeOverride = PixelTypes.Undefined)
-            => new LambdaProvider(func).Init(testMethod, pixelTypeOverride);
+            => new LambdaProvider(factoryFunc).Init(testMethod, pixelTypeOverride);
 
         public static TestImageProvider<TPixel> Solid(
             int width,
@@ -122,12 +121,7 @@ namespace ImageSharp.Tests
             }
             this.TypeName = typeName;
             this.MethodName = methodName;
-
-            if (pixelTypeOverride == PixelTypes.Rgba32)
-            {
-                this.Factory = new ImageFactory() as GenericFactory<TPixel>;
-            }
-
+            
             this.Utility = new ImagingTestCaseUtility
             {
                 SourceFileOrDescription = this.SourceFileOrDescription,
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageProviderTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageProviderTests.cs
index e9c4fc3d3d..f10ebeb301 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageProviderTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/TestImageProviderTests.cs
@@ -165,10 +165,10 @@ namespace ImageSharp.Tests
         /// <typeparam name="TPixel"></typeparam>
         /// <param name="factory"></param>
         /// <returns></returns>
-        public static Image<TPixel> CreateTestImage<TPixel>(GenericFactory<TPixel> factory)
+        public static Image<TPixel> CreateTestImage<TPixel>()
             where TPixel : struct, IPixel<TPixel>
         {
-            return factory.CreateImage(3, 3);
+            return new Image<TPixel>(3, 3);
         }
 
         [Theory]
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
index edee09c909..9a468da678 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
@@ -27,10 +27,10 @@ namespace ImageSharp.Tests
 
         private ITestOutputHelper Output { get; }
 
-        public static Image<TPixel> CreateTestImage<TPixel>(GenericFactory<TPixel> factory)
+        public static Image<TPixel> CreateTestImage<TPixel>()
             where TPixel : struct, IPixel<TPixel>
         {
-            Image<TPixel> image = factory.CreateImage(10, 10);
+            var image = new Image<TPixel>(10, 10);
 
             using (PixelAccessor<TPixel> pixels = image.Lock())
             {
@@ -38,10 +38,10 @@ namespace ImageSharp.Tests
                 {
                     for (int j = 0; j < 10; j++)
                     {
-                        Vector4 v = new Vector4(i, j, 0, 1);
+                        var v = new Vector4(i, j, 0, 1);
                         v /= 10;
 
-                        TPixel color = default(TPixel);
+                        var color = default(TPixel);
                         color.PackFromVector4(v);
 
                         pixels[i, j] = color;

From 1562e32046c0b6dd57e2cddcf5e5a5dbf9d3725f Mon Sep 17 00:00:00 2001
From: Anton Firszov <anton.firszov@sapagroup.com>
Date: Fri, 18 Aug 2017 18:09:18 +0200
Subject: [PATCH 2/4] Using Corecompat.System.Drawing as reference
 encoder/decoder for PNG. (Optimizing PNG-s with external tools from now.)

---
 src/ImageSharp/Configuration.cs               |  2 +-
 src/ImageSharp/Image/ImageExtensions.cs       |  2 +-
 .../Processors/Convolution/DetectEdgesTest.cs |  6 +-
 .../ImageProviders/FileProvider.cs            | 13 +----
 .../TestUtilities/ImagingTestCaseUtility.cs   | 42 +++++++-------
 ...er.cs => SystemDrawingReferenceDecoder.cs} |  4 +-
 ...er.cs => SystemDrawingReferenceEncoder.cs} |  6 +-
 .../TestUtilities/TestEnvironment.cs          | 58 +++++++++++++++++--
 .../TestUtilities/TestImageExtensions.cs      |  4 +-
 ...{TestUtilityExtensions.cs => TestUtils.cs} |  7 ++-
 .../Tests/ReferenceCodecTests.cs              |  4 +-
 .../Tests/TestEnvironmentTests.cs             | 24 ++++++++
 .../Tests/TestUtilityExtensionsTests.cs       |  2 +-
 tests/Images/External                         |  2 +-
 14 files changed, 117 insertions(+), 59 deletions(-)
 rename tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/{ReferenceDecoder.cs => SystemDrawingReferenceDecoder.cs} (90%)
 rename tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/{ReferenceEncoder.cs => SystemDrawingReferenceEncoder.cs} (72%)
 rename tests/ImageSharp.Tests/TestUtilities/{TestUtilityExtensions.cs => TestUtils.cs} (97%)

diff --git a/src/ImageSharp/Configuration.cs b/src/ImageSharp/Configuration.cs
index f169822858..12ceca0b28 100644
--- a/src/ImageSharp/Configuration.cs
+++ b/src/ImageSharp/Configuration.cs
@@ -140,7 +140,7 @@ namespace ImageSharp
         /// </summary>
         /// <param name="extension">The extension to discover</param>
         /// <returns>The <see cref="IImageFormat"/> if found otherwise null</returns>
-        public IImageFormat FindFormatByFileExtensions(string extension)
+        public IImageFormat FindFormatByFileExtension(string extension)
         {
             return this.imageFormats.FirstOrDefault(x => x.FileExtensions.Contains(extension, StringComparer.OrdinalIgnoreCase));
         }
diff --git a/src/ImageSharp/Image/ImageExtensions.cs b/src/ImageSharp/Image/ImageExtensions.cs
index 6095b49e3a..0eb3e2cab8 100644
--- a/src/ImageSharp/Image/ImageExtensions.cs
+++ b/src/ImageSharp/Image/ImageExtensions.cs
@@ -52,7 +52,7 @@ namespace ImageSharp
             Guard.NotNullOrEmpty(filePath, nameof(filePath));
 
             string ext = Path.GetExtension(filePath).Trim('.');
-            IImageFormat format = source.Configuration.FindFormatByFileExtensions(ext);
+            IImageFormat format = source.Configuration.FindFormatByFileExtension(ext);
             if (format == null)
             {
                 var stringBuilder = new StringBuilder();
diff --git a/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs b/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
index c753528f38..ee6650e55c 100644
--- a/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
+++ b/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
@@ -40,7 +40,7 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.Mutate(x => x.DetectEdges(detector));
-                image.DebugSave(provider, detector.ToString(), grayscale: true);
+                image.DebugSave(provider, detector.ToString());
             }
         }
 
@@ -52,7 +52,7 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
             using (Image<TPixel> image = provider.GetImage())
             {
                 image.Mutate(x => x.DetectEdges());
-                image.DebugSave(provider, grayscale: true);
+                image.DebugSave(provider);
             }
         }
 
@@ -79,7 +79,7 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
                 var bounds = new Rectangle(10, 10, image.Width / 2, image.Height / 2);
 
                 image.Mutate(x => x.DetectEdges(bounds));
-                image.DebugSave(provider, grayscale: true);
+                image.DebugSave(provider);
 
                 // TODO: We don't need this any longer after switching to ReferenceImages
                 ImageComparer.Tolerant().EnsureProcessorChangesAreConstrained(source, image, bounds);
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs
index 7ae103cd29..db30bb65d4 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageProviders/FileProvider.cs
@@ -45,17 +45,8 @@ namespace ImageSharp.Tests
 
             public override Image<TPixel> GetImage()
             {
-                Key key = new Key(this.PixelType, this.FilePath);
-
-                Image<TPixel> cachedImage = cache.GetOrAdd(
-                    key,
-                    fn =>
-                        {
-                            TestFile testFile = TestFile.Create(this.FilePath);
-                            return Image.Load<TPixel>(testFile.Bytes);
-                        });
-
-                return cachedImage.Clone();
+                IImageDecoder decoder = TestEnvironment.GetReferenceDecoder(this.FilePath);
+                return this.GetImage(decoder);
             }
 
             public override Image<TPixel> GetImage(IImageDecoder decoder)
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs b/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
index edb8bafac5..b157042b6e 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImagingTestCaseUtility.cs
@@ -138,13 +138,11 @@ namespace ImageSharp.Tests
             string extension = null,
             IImageEncoder encoder = null,
             object testOutputDetails = null,
-            bool grayscale = false,
             bool appendPixelTypeToFileName = true)
             where TPixel : struct, IPixel<TPixel>
         {
             string path = this.GetTestOutputFileName(extension, testOutputDetails, appendPixelTypeToFileName);
-            string extension1 = Path.GetExtension(path);
-            encoder = encoder ?? GetImageFormatByExtension(extension1, grayscale);
+            encoder = encoder ?? TestEnvironment.GetReferenceEncoder(path);
             
             using (FileStream stream = File.OpenWrite(path))
             {
@@ -173,26 +171,26 @@ namespace ImageSharp.Tests
             this.Init(method.DeclaringType.Name, method.Name);
         }
 
-        private static IImageEncoder GetImageFormatByExtension(string extension, bool grayscale)
-        {
-            extension = extension?.TrimStart('.');
-            var format = Configuration.Default.FindFormatByFileExtensions(extension);
-            IImageEncoder encoder = Configuration.Default.FindEncoder(format);
-            PngEncoder pngEncoder = encoder as PngEncoder;
-            if (pngEncoder != null)
-            {
-                pngEncoder = new PngEncoder();
-                encoder = pngEncoder;
-                pngEncoder.CompressionLevel = 9;
-
-                if (grayscale)
-                {
-                    pngEncoder.PngColorType = PngColorType.Grayscale;
-                }
-            }
+        //private static IImageEncoder GetEncoderByExtension(string extension, bool grayscale)
+        //{
+        //    extension = extension?.TrimStart('.');
+        //    var format = Configuration.Default.FindFormatByFileExtension(extension);
+        //    IImageEncoder encoder = Configuration.Default.FindEncoder(format);
+        //    PngEncoder pngEncoder = encoder as PngEncoder;
+        //    if (pngEncoder != null)
+        //    {
+        //        pngEncoder = new PngEncoder();
+        //        encoder = pngEncoder;
+        //        pngEncoder.CompressionLevel = 9;
+
+        //        if (grayscale)
+        //        {
+        //            pngEncoder.PngColorType = PngColorType.Grayscale;
+        //        }
+        //    }
             
-            return encoder;
-        }
+        //    return encoder;
+        //}
 
         private string GetTestOutputDir()
         {
diff --git a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceDecoder.cs b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceDecoder.cs
similarity index 90%
rename from tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceDecoder.cs
rename to tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceDecoder.cs
index 3ed3248b26..493866170a 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceDecoder.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceDecoder.cs
@@ -8,9 +8,9 @@ namespace ImageSharp.Tests.TestUtilities.ReferenceCodecs
     using ImageSharp.Formats;
     using ImageSharp.PixelFormats;
 
-    public class ReferenceDecoder : IImageDecoder
+    public class SystemDrawingReferenceDecoder : IImageDecoder
     {
-        public static ReferenceDecoder Instance { get; } = new ReferenceDecoder();
+        public static SystemDrawingReferenceDecoder Instance { get; } = new SystemDrawingReferenceDecoder();
 
         public Image<TPixel> Decode<TPixel>(Configuration configuration, Stream stream)
             where TPixel : struct, IPixel<TPixel>
diff --git a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceEncoder.cs b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceEncoder.cs
similarity index 72%
rename from tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceEncoder.cs
rename to tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceEncoder.cs
index 9018d66f7f..c1c10c469a 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/ReferenceEncoder.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/SystemDrawingReferenceEncoder.cs
@@ -9,16 +9,16 @@ namespace ImageSharp.Tests.TestUtilities.ReferenceCodecs
     using ImageSharp.Formats;
     using ImageSharp.PixelFormats;
 
-    public class ReferenceEncoder : IImageEncoder
+    public class SystemDrawingReferenceEncoder : IImageEncoder
     {
         private readonly System.Drawing.Imaging.ImageFormat imageFormat;
 
-        public ReferenceEncoder(ImageFormat imageFormat)
+        public SystemDrawingReferenceEncoder(ImageFormat imageFormat)
         {
             this.imageFormat = imageFormat;
         }
 
-        public static ReferenceEncoder Png { get; } = new ReferenceEncoder(System.Drawing.Imaging.ImageFormat.Png);
+        public static SystemDrawingReferenceEncoder Png { get; } = new SystemDrawingReferenceEncoder(System.Drawing.Imaging.ImageFormat.Png);
 
         public void Encode<TPixel>(Image<TPixel> image, Stream stream)
             where TPixel : struct, IPixel<TPixel>
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
index 728cf45696..7cfc5c6e40 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
@@ -1,12 +1,13 @@
 namespace ImageSharp.Tests
 {
     using System;
-    using System.Collections.Generic;
     using System.IO;
     using System.Linq;
     using System.Reflection;
-    using System.Security;
 
+    using ImageSharp.Formats;
+    using ImageSharp.Tests.TestUtilities.ReferenceCodecs;
+    
     public static class TestEnvironment
     {
         private const string ImageSharpSolutionFileName = "ImageSharp.sln";
@@ -26,6 +27,8 @@ namespace ImageSharp.Tests
                     return bool.TryParse(Environment.GetEnvironmentVariable("CI"), out isCi) && isCi;
                 });
 
+        private static Lazy<Configuration> configuration = new Lazy<Configuration>(CreateDefaultConfiguration);
+        
         // ReSharper disable once InconsistentNaming
         /// <summary>
         /// Gets a value indicating whether test execution runs on CI.
@@ -34,6 +37,24 @@ namespace ImageSharp.Tests
 
         internal static string SolutionDirectoryFullPath => solutionDirectoryFullPath.Value;
 
+        internal static Configuration Configuration => configuration.Value;
+
+        private static Configuration CreateDefaultConfiguration()
+        {
+            var configuration = new Configuration(
+                new PngConfigurationModule(),
+                new JpegConfigurationModule(),
+                new GifConfigurationModule(),
+                new BmpConfigurationModule()
+                );
+
+            configuration.SetDecoder(ImageFormats.Png, SystemDrawingReferenceDecoder.Instance);
+            configuration.SetEncoder(ImageFormats.Png, SystemDrawingReferenceEncoder.Png);
+            configuration.AddImageFormatDetector(new PngImageFormatDetector());
+
+            return configuration;
+        }
+
         private static string GetSolutionDirectoryFullPathImpl()
         {
             string assemblyLocation = typeof(TestFile).GetTypeInfo().Assembly.Location;
@@ -62,23 +83,48 @@ namespace ImageSharp.Tests
 
             return directory.FullName;
         }
-       
+
         /// <summary>
         /// Gets the correct full path to the Input Images directory.
         /// </summary>
-        internal static string InputImagesDirectoryFullPath => Path.Combine(SolutionDirectoryFullPath, InputImagesRelativePath);
+        internal static string InputImagesDirectoryFullPath =>
+            Path.Combine(SolutionDirectoryFullPath, InputImagesRelativePath);
 
         /// <summary>
         /// Gets the correct full path to the Actual Output directory. (To be written to by the test cases.)
         /// </summary>
-        internal static string ActualOutputDirectoryFullPath => Path.Combine(SolutionDirectoryFullPath, ActualOutputDirectoryRelativePath);
+        internal static string ActualOutputDirectoryFullPath => Path.Combine(
+            SolutionDirectoryFullPath,
+            ActualOutputDirectoryRelativePath);
 
         /// <summary>
         /// Gets the correct full path to the Expected Output directory. (To compare the test results to.)
         /// </summary>
-        internal static string ReferenceOutputDirectoryFullPath => Path.Combine(SolutionDirectoryFullPath, ReferenceOutputDirectoryRelativePath);
+        internal static string ReferenceOutputDirectoryFullPath => Path.Combine(
+            SolutionDirectoryFullPath,
+            ReferenceOutputDirectoryRelativePath);
 
         internal static string GetReferenceOutputFileName(string actualOutputFileName) =>
             actualOutputFileName.Replace("ActualOutput", @"External\ReferenceOutput");
+
+        internal static IImageDecoder GetReferenceDecoder(string filePath)
+        {
+            IImageFormat format = GetImageFormat(filePath);
+            return Configuration.FindDecoder(format);
+        }
+
+        internal static IImageEncoder GetReferenceEncoder(string filePath)
+        {
+            IImageFormat format = GetImageFormat(filePath);
+            return Configuration.FindEncoder(format);
+        }
+
+        private static IImageFormat GetImageFormat(string filePath)
+        {
+            string extension = Path.GetExtension(filePath).ToLower();
+            if (extension[0] == '.') extension = extension.Substring(1);
+            IImageFormat format = Configuration.FindFormatByFileExtension(extension);
+            return format;
+        }
     }
 }
\ No newline at end of file
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
index 35a7d17d40..e4563df4fd 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
@@ -29,7 +29,6 @@ namespace ImageSharp.Tests
             ITestImageProvider provider,
             object testOutputDetails = null,
             string extension = "png",
-            bool grayscale = false,
             bool appendPixelTypeToFileName = true)
             where TPixel : struct, IPixel<TPixel>
         {
@@ -43,7 +42,6 @@ namespace ImageSharp.Tests
                 image,
                 extension,
                 testOutputDetails: testOutputDetails,
-                grayscale: grayscale,
                 appendPixelTypeToFileName: appendPixelTypeToFileName);
             return image;
         }
@@ -139,7 +137,7 @@ namespace ImageSharp.Tests
 
             var testFile = TestFile.Create(path);
 
-            using (var original = Image.Load<TPixel>(testFile.Bytes, ReferenceDecoder.Instance))
+            using (var original = Image.Load<TPixel>(testFile.Bytes, SystemDrawingReferenceDecoder.Instance))
             {
                 //original.DebugSave(provider, "__SYSTEMDRAWING__");
                 comparer.VerifySimilarity(original, image);
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestUtilityExtensions.cs b/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
similarity index 97%
rename from tests/ImageSharp.Tests/TestUtilities/TestUtilityExtensions.cs
rename to tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
index 835561fe0f..21ef03fa6f 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestUtilityExtensions.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestUtils.cs
@@ -11,12 +11,13 @@ namespace ImageSharp.Tests
     using System.Linq;
     using System.Reflection;
 
+    using ImageSharp.Formats;
     using ImageSharp.PixelFormats;
 
     /// <summary>
-    /// Extension methods for TestUtilities
+    /// Various utility and extension methods.
     /// </summary>
-    public static class TestUtilityExtensions
+    public static class TestUtils
     {
         private static readonly Dictionary<Type, PixelTypes> ClrTypes2PixelTypes = new Dictionary<Type, PixelTypes>();
 
@@ -28,7 +29,7 @@ namespace ImageSharp.Tests
             .Except(new[] { PixelTypes.Undefined, PixelTypes.All })
             .ToArray();
 
-        static TestUtilityExtensions()
+        static TestUtils()
         {
             // Add Rgba32 Our default.
             Type defaultPixelFormatType = typeof(Rgba32);
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/ReferenceCodecTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/ReferenceCodecTests.cs
index 51b5f49b61..6e3afbcae2 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/ReferenceCodecTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/ReferenceCodecTests.cs
@@ -52,7 +52,7 @@ namespace ImageSharp.Tests
             where TPixel : struct, IPixel<TPixel>
         {
             string path = TestFile.GetInputFileFullPath(TestImages.Png.Splash);
-            using (Image<TPixel> image = Image.Load<TPixel>(path, ReferenceDecoder.Instance))
+            using (Image<TPixel> image = Image.Load<TPixel>(path, SystemDrawingReferenceDecoder.Instance))
             {
                 image.DebugSave(dummyProvider);
             }
@@ -65,7 +65,7 @@ namespace ImageSharp.Tests
         {
             using (Image<TPixel> image = provider.GetImage())
             {
-                provider.Utility.SaveTestOutputFile(image, "png", ReferenceEncoder.Png);
+                provider.Utility.SaveTestOutputFile(image, "png", SystemDrawingReferenceEncoder.Png);
             }
         }
     }
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs
index ac537b3c39..10e08b5de0 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/TestEnvironmentTests.cs
@@ -6,8 +6,12 @@
 // ReSharper disable InconsistentNaming
 namespace ImageSharp.Tests
 {
+    using System;
     using System.IO;
 
+    using ImageSharp.Formats;
+    using ImageSharp.Tests.TestUtilities.ReferenceCodecs;
+
     using Xunit;
     using Xunit.Abstractions;
     
@@ -59,5 +63,25 @@ namespace ImageSharp.Tests
             this.Output.WriteLine(expected);
             Assert.Contains(TestEnvironment.ReferenceOutputDirectoryFullPath, expected);
         }
+
+        [Theory]
+        [InlineData("lol/foo.png", typeof(SystemDrawingReferenceEncoder))]
+        [InlineData("lol/Baz.JPG", typeof(JpegEncoder))]
+        [InlineData("lol/Baz.gif", typeof(GifEncoder))]
+        public void GetReferenceEncoder_ReturnsCorrectEncoders(string fileName, Type expectedEncoderType)
+        {
+            IImageEncoder encoder = TestEnvironment.GetReferenceEncoder(fileName);
+            Assert.IsType(expectedEncoderType, encoder);
+        }
+
+        [Theory]
+        [InlineData("lol/foo.png", typeof(SystemDrawingReferenceDecoder))]
+        [InlineData("lol/Baz.JPG", typeof(JpegDecoder))]
+        [InlineData("lol/Baz.gif", typeof(GifDecoder))]
+        public void GetReferenceDecoder_ReturnsCorrectEncoders(string fileName, Type expectedDecoderType)
+        {
+            IImageDecoder decoder = TestEnvironment.GetReferenceDecoder(fileName);
+            Assert.IsType(expectedDecoderType, decoder);
+        }
     }
 }
diff --git a/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs b/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
index 9a468da678..8651d246bc 100644
--- a/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/Tests/TestUtilityExtensionsTests.cs
@@ -147,7 +147,7 @@ namespace ImageSharp.Tests
         {
             KeyValuePair<PixelTypes, Type>[] expanded = PixelTypes.All.ExpandAllTypes().ToArray();
 
-            Assert.True(expanded.Length >= TestUtilityExtensions.GetAllPixelTypes().Length - 2);
+            Assert.True(expanded.Length >= TestUtils.GetAllPixelTypes().Length - 2);
             AssertContainsPixelType<Rgba32>(PixelTypes.Rgba32, expanded);
             AssertContainsPixelType<Rgba32>(PixelTypes.Rgba32, expanded);
         }
diff --git a/tests/Images/External b/tests/Images/External
index 6996009ff5..4929cbe0d7 160000
--- a/tests/Images/External
+++ b/tests/Images/External
@@ -1 +1 @@
-Subproject commit 6996009ff537d1c9cbc2b93d692cd89bf8f2a5c7
+Subproject commit 4929cbe0d743fe3c67a9b4d0c71fb3eed8b5537d

From 02eb5f2f135ed2568a03bdfa9f847b65e2f00e00 Mon Sep 17 00:00:00 2001
From: Anton Firszov <anton.firszov@sapagroup.com>
Date: Fri, 18 Aug 2017 18:37:16 +0200
Subject: [PATCH 3/4] PngDecoder is covered now, and proven to be buggy :P

---
 .../Formats/Png/PngDecoderTests.cs               |  12 ++++++++----
 tests/ImageSharp.Tests/TestImages.cs             |   1 +
 .../ImageComparison/ImageComparer.cs             |   2 +-
 .../ImageComparison/TolerantImageComparer.cs     |   4 ++--
 .../TestUtilities/TestEnvironment.cs             |   2 +-
 .../TestUtilities/TestImageExtensions.cs         |  14 ++++++++++++--
 tests/Images/Input/Png/SnakeGame.png             | Bin 0 -> 6958 bytes
 7 files changed, 25 insertions(+), 10 deletions(-)
 create mode 100644 tests/Images/Input/Png/SnakeGame.png

diff --git a/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs b/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs
index 5f4055a936..1d40163d10 100644
--- a/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs
+++ b/tests/ImageSharp.Tests/Formats/Png/PngDecoderTests.cs
@@ -12,6 +12,8 @@ using Xunit;
 
 namespace ImageSharp.Tests
 {
+    using ImageSharp.Tests.TestUtilities.ImageComparison;
+
     public class PngDecoderTests
     {
         private const PixelTypes PixelTypes = Tests.PixelTypes.Rgba32 | Tests.PixelTypes.RgbaVector | Tests.PixelTypes.Argb32;
@@ -19,17 +21,19 @@ namespace ImageSharp.Tests
         public static readonly string[] TestFiles =
             {
                 TestImages.Png.Splash, TestImages.Png.Indexed, TestImages.Png.Interlaced, TestImages.Png.FilterVar,
-                TestImages.Png.Bad.ChunkLength1, TestImages.Png.Bad.ChunkLength2, TestImages.Png.Rgb48Bpp, TestImages.Png.Rgb48BppInterlaced
+                TestImages.Png.Bad.ChunkLength1, TestImages.Png.Bad.ChunkLength2, TestImages.Png.Rgb48Bpp,
+                TestImages.Png.Rgb48BppInterlaced, TestImages.Png.SnakeGame
             };
 
         [Theory]
         [WithFileCollection(nameof(TestFiles), PixelTypes)]
-        public void Decode<TPixel>(TestImageProvider<TPixel> imageProvider)
+        public void Decode<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = imageProvider.GetImage())
+            using (Image<TPixel> image = provider.GetImage(new PngDecoder()))
             {
-                image.DebugSave(imageProvider);
+                image.DebugSave(provider);
+                image.CompareToOriginal(provider, ImageComparer.Exact);
             }
         }
 
diff --git a/tests/ImageSharp.Tests/TestImages.cs b/tests/ImageSharp.Tests/TestImages.cs
index 527b78ae6b..66ca93bd23 100644
--- a/tests/ImageSharp.Tests/TestImages.cs
+++ b/tests/ImageSharp.Tests/TestImages.cs
@@ -31,6 +31,7 @@ namespace ImageSharp.Tests
             public const string Bike = "Png/Bike.png";
             public const string BikeGrayscale = "Png/BikeGrayscale.png";
             public const string Rgb48BppInterlaced = "Png/rgb-48bpp-interlaced.png";
+            public const string SnakeGame = "Png/SnakeGame.png";
 
             // Filtered test images from http://www.schaik.com/pngsuite/pngsuite_fil_png.html
             public const string Filter0 = "Png/filter0.png";
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparer.cs b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparer.cs
index b13905ef57..80102e6010 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparer.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/ImageComparer.cs
@@ -10,7 +10,7 @@ namespace ImageSharp.Tests.TestUtilities.ImageComparison
 
     public abstract class ImageComparer
     {
-        public static ImageComparer Exact { get; } = ExactImageComparer.Instance;
+        public static ImageComparer Exact { get; } = Tolerant(0, 0);
 
         public static ImageComparer Tolerant(
             float imageThreshold = TolerantImageComparer.DefaultImageThreshold,
diff --git a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
index 23e5761806..0351b00200 100644
--- a/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/ImageComparison/TolerantImageComparer.cs
@@ -66,7 +66,7 @@
 
                 for (int x = 0; x < width; x++)
                 {
-                    int d = GetDifferenceInPixelByteSum(ref aBuffer[x], ref bBuffer[x]);
+                    int d = GetHammingDistanceInRgbaSpace(ref aBuffer[x], ref bBuffer[x]);
 
                     if (d > this.PixelThresholdInPixelByteSum)
                     {
@@ -92,7 +92,7 @@
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static int GetDifferenceInPixelByteSum(ref Rgba32 a, ref Rgba32 b)
+        private static int GetHammingDistanceInRgbaSpace(ref Rgba32 a, ref Rgba32 b)
         {
             return Diff(a.R, b.R) + Diff(a.G, b.G) + Diff(a.B, b.B) + Diff(a.A, b.A);
         }
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
index 7cfc5c6e40..9b2f7c479e 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestEnvironment.cs
@@ -119,7 +119,7 @@ namespace ImageSharp.Tests
             return Configuration.FindEncoder(format);
         }
 
-        private static IImageFormat GetImageFormat(string filePath)
+        internal static IImageFormat GetImageFormat(string filePath)
         {
             string extension = Path.GetExtension(filePath).ToLower();
             if (extension[0] == '.') extension = extension.Substring(1);
diff --git a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
index e4563df4fd..17d75ff3f2 100644
--- a/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
+++ b/tests/ImageSharp.Tests/TestUtilities/TestImageExtensions.cs
@@ -7,7 +7,9 @@ namespace ImageSharp.Tests
 {
     using System;
     using System.IO;
+    using System.Linq;
 
+    using ImageSharp.Formats;
     using ImageSharp.PixelFormats;
     using ImageSharp.Tests.TestUtilities.ImageComparison;
     using ImageSharp.Tests.TestUtilities.ReferenceCodecs;
@@ -137,9 +139,17 @@ namespace ImageSharp.Tests
 
             var testFile = TestFile.Create(path);
 
-            using (var original = Image.Load<TPixel>(testFile.Bytes, SystemDrawingReferenceDecoder.Instance))
+            IImageDecoder referenceDecoder = TestEnvironment.GetReferenceDecoder(path);
+            IImageFormat format = TestEnvironment.GetImageFormat(path);
+            IImageDecoder defaultDecoder = Configuration.Default.FindDecoder(format);
+
+            if (referenceDecoder.GetType() == defaultDecoder.GetType())
+            {
+                throw new InvalidOperationException($"Can't use CompareToOriginal(): no actual reference decoder registered for {format.Name}");
+            }
+
+            using (var original = Image.Load<TPixel>(testFile.Bytes, referenceDecoder))
             {
-                //original.DebugSave(provider, "__SYSTEMDRAWING__");
                 comparer.VerifySimilarity(original, image);
             }
 
diff --git a/tests/Images/Input/Png/SnakeGame.png b/tests/Images/Input/Png/SnakeGame.png
new file mode 100644
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HcmV?d00001


From 1df0010140c8ec833a619b084dec1fb124756d5b Mon Sep 17 00:00:00 2001
From: Anton Firszov <anton.firszov@sapagroup.com>
Date: Fri, 18 Aug 2017 18:56:27 +0200
Subject: [PATCH 4/4] covered DetectEdges

---
 .../Processing/Processors/Convolution/DetectEdgesTest.cs  | 8 +++++---
 tests/Images/External                                     | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs b/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
index ee6650e55c..cdb48bdd2f 100644
--- a/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
+++ b/tests/ImageSharp.Tests/Processing/Processors/Convolution/DetectEdgesTest.cs
@@ -41,6 +41,7 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
             {
                 image.Mutate(x => x.DetectEdges(detector));
                 image.DebugSave(provider, detector.ToString());
+                image.CompareToReferenceOutput(provider, detector.ToString());
             }
         }
 
@@ -53,6 +54,7 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
             {
                 image.Mutate(x => x.DetectEdges());
                 image.DebugSave(provider);
+                image.CompareToReferenceOutput(provider);
             }
         }
 
@@ -73,16 +75,16 @@ namespace ImageSharp.Tests.Processing.Processors.Convolution
         public void DetectEdges_InBox<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> source = provider.GetImage())
-            using (Image<TPixel> image = source.Clone())
+            using (Image<TPixel> image = provider.GetImage())
             {
                 var bounds = new Rectangle(10, 10, image.Width / 2, image.Height / 2);
 
                 image.Mutate(x => x.DetectEdges(bounds));
                 image.DebugSave(provider);
+                image.CompareToReferenceOutput(provider);
 
                 // TODO: We don't need this any longer after switching to ReferenceImages
-                ImageComparer.Tolerant().EnsureProcessorChangesAreConstrained(source, image, bounds);
+                //ImageComparer.Tolerant().EnsureProcessorChangesAreConstrained(source, image, bounds);
             }
         }
     }
diff --git a/tests/Images/External b/tests/Images/External
index 4929cbe0d7..b466db97b5 160000
--- a/tests/Images/External
+++ b/tests/Images/External
@@ -1 +1 @@
-Subproject commit 4929cbe0d743fe3c67a9b4d0c71fb3eed8b5537d
+Subproject commit b466db97b501bcd12a7e366ee1d2d6a6e45eb2d0