added unit tests for adaptive histogram equalization

tests/ImageSharp.Tests/Processing/Normalization/HistogramEqualizationTests.cs

@@ -4,12 +4,15 @@
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing;
 using SixLabors.ImageSharp.Processing.Processors.Normalization;
+using SixLabors.ImageSharp.Tests.TestUtilities.ImageComparison;
 using Xunit;
 
 namespace SixLabors.ImageSharp.Tests.Processing.Normalization
 {
     public class HistogramEqualizationTests
     {
+        private static readonly ImageComparer ValidatorComparer = ImageComparer.TolerantPercentage(0.0456F);
+
         [Theory]
         [InlineData(256)]
         [InlineData(65536)]
@@ -68,5 +71,45 @@ namespace SixLabors.ImageSharp.Tests.Processing.Normalization
                 }
             }
         }
+
+        [Theory]
+        [WithFile(TestImages.Jpeg.Baseline.LowContrast, PixelTypes.Rgba32)]
+        public void Adaptive_SlidingWindow_15Tiles_WithClipping<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                var options = new HistogramEqualizationOptions()
+                                  {
+                                      Method = HistogramEqualizationMethod.AdaptiveSlidingWindow,
+                                      LuminanceLevels = 256,
+                                      ClipHistogram = true,
+                                      Tiles = 15
+                                  };
+                image.Mutate(x => x.HistogramEqualization(options));
+                image.DebugSave(provider);
+                image.CompareToReferenceOutput(ValidatorComparer, provider);
+            }
+        }
+
+        [Theory]
+        [WithFile(TestImages.Jpeg.Baseline.LowContrast, PixelTypes.Rgba32)]
+        public void Adaptive_TileInterpolation_10Tiles_WithClipping<TPixel>(TestImageProvider<TPixel> provider)
+            where TPixel : struct, IPixel<TPixel>
+        {
+            using (Image<TPixel> image = provider.GetImage())
+            {
+                var options = new HistogramEqualizationOptions()
+                                  {
+                                      Method = HistogramEqualizationMethod.AdaptiveTileInterpolation,
+                                      LuminanceLevels = 256,
+                                      ClipHistogram = true,
+                                      Tiles = 10
+                                  };
+                image.Mutate(x => x.HistogramEqualization(options));
+                image.DebugSave(provider);
+                image.CompareToReferenceOutput(ValidatorComparer, provider);
+            }
+        }
     }
 }

tests/ImageSharp.Tests/TestImages.cs

@@ -135,6 +135,7 @@ namespace SixLabors.ImageSharp.Tests
                 public const string Testorig420 = "Jpg/baseline/testorig.jpg";
                 public const string MultiScanBaselineCMYK = "Jpg/baseline/MultiScanBaselineCMYK.jpg";
                 public const string Ratio1x1 = "Jpg/baseline/ratio-1x1.jpg";
+                public const string LowContrast = "Jpg/baseline/AsianCarvingLowContrast.jpg";
 
                 public static readonly string[] All =
                 {

tests/Images/External

@@ -1 +1 @@
-Subproject commit 69603ee5b6f7dd64114fc44d321e50d9b2d439be
+Subproject commit 9a852d6fa566d5a88f989093f9430ee54f784e53