reference images for filter tests + DRY out repeated code

tests/ImageSharp.Tests/Processing/Processors/Filters/BlackWhiteTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyBlackWhiteFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.BlackWhite());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(ctx => ctx.BlackWhite());
         }
 
         [Theory]
@@ -29,6 +25,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyBlackWhiteFilterInBox<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
+            // TODO: We need a DRY-refactor on these tests for all Filter tests!
             using (Image<TPixel> source = provider.GetImage())
             using (Image<TPixel> image = source.Clone())
             {

tests/ImageSharp.Tests/Processing/Processors/Filters/BrightnessTest.cs

@@ -24,11 +24,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Effects
         public void ApplyBrightnessFilter<TPixel>(TestImageProvider<TPixel> provider, float value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Brightness(value));
-                image.DebugSave(provider, value);
-            }
+            provider.RunValidatingProcessorTest(ctx => ctx.Brightness(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/ColorBlindnessTest.cs

@@ -31,11 +31,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyColorBlindnessFilter<TPixel>(TestImageProvider<TPixel> provider, ColorBlindness colorBlindness)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.ColorBlindness(colorBlindness));
-                image.DebugSave(provider, colorBlindness.ToString());
-            }
+            provider.RunValidatingProcessorTest(x => x.ColorBlindness(colorBlindness), colorBlindness.ToString());
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/ContrastTest.cs

@@ -24,11 +24,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Effects
         public void ApplyContrastFilter<TPixel>(TestImageProvider<TPixel> provider, float value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Contrast(value));
-                image.DebugSave(provider, value);
-            }
+            provider.RunValidatingProcessorTest(x => x.Contrast(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/FilterTest.cs

@@ -21,14 +21,12 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                Matrix4x4 brightness = MatrixFilters.CreateBrightnessFilter(0.9F);
-                Matrix4x4 hue = MatrixFilters.CreateHueFilter(180F);
-                Matrix4x4 saturation = MatrixFilters.CreateSaturateFilter(1.5F);
-                image.Mutate(x => x.Filter(brightness * hue * saturation));
-                image.DebugSave(provider);
-            }
+            Matrix4x4 brightness = MatrixFilters.CreateBrightnessFilter(0.9F);
+            Matrix4x4 hue = MatrixFilters.CreateHueFilter(180F);
+            Matrix4x4 saturation = MatrixFilters.CreateSaturateFilter(1.5F);
+            Matrix4x4 m = brightness * hue * saturation;
+
+            provider.RunValidatingProcessorTest(x => x.Filter(m));
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/GrayscaleTest.cs

@@ -29,20 +29,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyGrayscaleFilter<TPixel>(TestImageProvider<TPixel> provider, GrayscaleMode value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Grayscale(value));
-                var rgb = default(Rgb24);
-                System.Span<TPixel> span = image.Frames.RootFrame.GetPixelSpan();
-                for (int i = 0; i < span.Length; i++)
-                {
-                    span[i].ToRgb24(ref rgb);
-                    Assert.Equal(rgb.R, rgb.B);
-                    Assert.Equal(rgb.B, rgb.G);
-                }
-
-                image.DebugSave(provider, value.ToString());
-            }
+            provider.RunValidatingProcessorTest(x => x.Grayscale(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/HueTest.cs

@@ -24,11 +24,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyHueFilter<TPixel>(TestImageProvider<TPixel> provider, int value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Hue(value));
-                image.DebugSave(provider, value);
-            }
+            provider.RunValidatingProcessorTest(x => x.Hue(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/InvertTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Effects
         public void ApplyInvertFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Invert());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(x => x.Invert());
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/KodachromeTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyKodachromeFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Kodachrome());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(x => x.Kodachrome());
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/LomographTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyLomographFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Lomograph());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(x => x.Lomograph());
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/OpacityTest.cs

@@ -24,11 +24,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Effects
         public void ApplyAlphaFilter<TPixel>(TestImageProvider<TPixel> provider, float value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Opacity(value));
-                image.DebugSave(provider, value);
-            }
+            provider.RunValidatingProcessorTest(x => x.Opacity(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/PolaroidTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplyPolaroidFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Polaroid());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(x => x.Polaroid());
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/SaturateTest.cs

@@ -24,11 +24,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplySaturationFilter<TPixel>(TestImageProvider<TPixel> provider, float value)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Saturate(value));
-                image.DebugSave(provider, value);
-            }
+            provider.RunValidatingProcessorTest(x => x.Saturate(value), value);
         }
 
         [Theory]

tests/ImageSharp.Tests/Processing/Processors/Filters/SepiaTest.cs

@@ -17,11 +17,7 @@ namespace SixLabors.ImageSharp.Tests.Processing.Processors.Filters
         public void ApplySepiaFilter<TPixel>(TestImageProvider<TPixel> provider)
             where TPixel : struct, IPixel<TPixel>
         {
-            using (Image<TPixel> image = provider.GetImage())
-            {
-                image.Mutate(x => x.Sepia());
-                image.DebugSave(provider);
-            }
+            provider.RunValidatingProcessorTest(x => x.Sepia());
         }
 
         [Theory]

tests/ImageSharp.Tests/TestUtilities/TestUtils.cs

@@ -10,6 +10,8 @@ using SixLabors.ImageSharp.PixelFormats;
 
 namespace SixLabors.ImageSharp.Tests
 {
+    using SixLabors.Primitives;
+
     /// <summary>
     /// Various utility and extension methods.
     /// </summary>
@@ -142,5 +144,56 @@ namespace SixLabors.ImageSharp.Tests
         /// </summary>
         /// <returns>The pixel types</returns>
         internal static PixelTypes[] GetAllPixelTypes() => (PixelTypes[])Enum.GetValues(typeof(PixelTypes));
+
+        /// <summary>
+        /// Utility for testing image processor extension methods:
+        /// 1. Run a processor defined by 'process'
+        /// 2. Run 'DebugSave()' to save the output locally
+        /// 3. Run 'CompareToReferenceOutput()' to compare the results to the expected output
+        /// </summary>
+        internal static void RunValidatingProcessorTest<TPixel>(
+            this TestImageProvider<TPixel> provider,
+            Action<IImageProcessingContext<TPixel>> process,
+            object testOutputDetails = null)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                image.Mutate(process);
+                image.DebugSave(provider, testOutputDetails);
+                image.CompareToReferenceOutput(provider, testOutputDetails);
+            }
+        }
+
+        internal static void RunRectangleConstrainedValidatingProcessorTest<TPixel>(
+            this TestImageProvider<TPixel> provider,
+            Action<IImageProcessingContext<TPixel>, Rectangle> process,
+            object testOutputDetails = null)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                var bounds = new Rectangle(image.Width / 4, image.Width / 4, image.Width / 2, image.Height / 2);
+                image.Mutate(x => process(x, bounds));
+                image.DebugSave(provider, testOutputDetails);
+                image.CompareToReferenceOutput(provider, testOutputDetails);
+            }
+        }
+
+        /// <summary>
+        /// Same as <see cref="RunValidatingProcessorTest{TPixel}"/> but without the 'CompareToReferenceOutput()' step.
+        /// </summary>
+        internal static void RunProcessorTest<TPixel>(
+            this TestImageProvider<TPixel> provider,
+            Action<IImageProcessingContext<TPixel>> process,
+            object testOutputDetails = null)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                image.Mutate(process);
+                image.DebugSave(provider, testOutputDetails);
+            }
+        }
     }
 }

tests/Images/External

@@ -1 +1 @@
-Subproject commit dc5479d00b2312f691e6249b9f7765e2316d4a30
+Subproject commit e12e75f12925de1b88dc7e564c509ee896aa5f53