Add sse tests for inverse transform

src/ImageSharp/Formats/Webp/Lossy/Vp8Encoding.cs

@@ -87,7 +87,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
         {
 #if SUPPORTS_RUNTIME_INTRINSICS
             if (Sse2.IsSupported)
-            //if (false)
             {
                 // This implementation makes use of 16-bit fixed point versions of two
                 // multiply constants:

tests/ImageSharp.Tests/Formats/WebP/Vp8EncodingTests.cs

@@ -0,0 +1,57 @@
+// Copyright (c) Six Labors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Linq;
+using SixLabors.ImageSharp.Formats.Webp.Lossy;
+using SixLabors.ImageSharp.Tests.TestUtilities;
+using Xunit;
+
+namespace SixLabors.ImageSharp.Tests.Formats.WebP
+{
+    [Trait("Format", "Webp")]
+    public class Vp8EncodingTests
+    {
+        private static void RunInverseTransformTest()
+        {
+            // arrange
+            byte[] reference =
+            {
+                128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129,
+                129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 128, 128, 128, 128, 128, 128, 128, 128,
+                128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129,
+                129, 129, 129, 129, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128,
+                129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 129, 128, 128, 128, 128,
+                128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 128, 129, 129, 129, 129, 129, 129, 129, 129,
+                129, 129, 129, 129, 129, 129, 129, 129
+            };
+            short[] input = { 177, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 177, -24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+            byte[] dst = new byte[128];
+            byte[] expected =
+            {
+                150, 150, 150, 150, 146, 149, 152, 154, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 150, 150, 150, 150, 146, 149, 152, 154, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 0, 0, 0, 0, 150, 150, 150, 150, 146, 149, 152, 154, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 150, 150, 150, 150, 146, 149, 152, 154, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+            };
+            int[] scratch = new int[16];
+
+            // act
+            Vp8Encoding.ITransform(reference, input, dst, true, scratch);
+
+            // assert
+            Assert.True(dst.SequenceEqual(expected));
+        }
+
+        [Fact]
+        public void InverseTransform_Works() => RunInverseTransformTest();
+
+#if SUPPORTS_RUNTIME_INTRINSICS
+        [Fact]
+        public void InverseTransform_WithHardwareIntrinsics_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunInverseTransformTest, HwIntrinsics.AllowAll);
+
+        [Fact]
+        public void InverseTransform_WithoutHardwareIntrinsics_Works() => FeatureTestRunner.RunWithHwIntrinsicsFeature(RunInverseTransformTest, HwIntrinsics.DisableHWIntrinsic);
+#endif
+    }
+}