Merge pull request #1922 from br3aker/dp/jpeg-idct-scalar

Fixed Jpeg IDCT missing scalar implementation
SixLabors · Jan 4, 2022 · f7b332a · f7b332a
2 parents fe044d1 + d61b845
commit f7b332a
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Showing 2 changed files with 10 additions and 8 deletions.
diff --git a/src/ImageSharp/Formats/Jpeg/Components/FastFloatingPointDCT.cs b/src/ImageSharp/Formats/Jpeg/Components/FastFloatingPointDCT.cs
@@ -146,11 +146,13 @@ public static void TransformFDCT(ref Block8x8F block)
         /// <summary>
         /// Apply floating point IDCT inplace using <see cref="Vector4"/> API.
         /// </summary>
+        /// <remarks>
+        /// This method can be used even if there's no SIMD intrinsics available
+        /// as <see cref="Vector4"/> can be compiled to scalar instructions.
+        /// </remarks>
         /// <param name="transposedBlock">Input block.</param>
         private static void IDCT_Vector4(ref Block8x8F transposedBlock)
         {
-            DebugGuard.IsTrue(Vector.IsHardwareAccelerated, "Scalar implementation should be called for non-accelerated hardware.");
-
             // First pass - process columns
             IDCT8x4_Vector4(ref transposedBlock.V0L);
             IDCT8x4_Vector4(ref transposedBlock.V0R);

diff --git a/tests/ImageSharp.Tests/Formats/Jpg/DCTTests.cs b/tests/ImageSharp.Tests/Formats/Jpg/DCTTests.cs
@@ -149,12 +149,12 @@ static void RunTest(string serialized)
                 // 4 paths:
                 // 1. AllowAll - call avx/fma implementation
                 // 2. DisableFMA - call avx without fma implementation
-                // 3. DisableAvx - call sse Vector4 implementation
-                // 4. DisableHWIntrinsic - call scalar fallback implementation
+                // 3. DisableAvx - call sse implementation
+                // 4. DisableSIMD - call Vector4 fallback implementation
                 FeatureTestRunner.RunWithHwIntrinsicsFeature(
                     RunTest,
                     seed,
-                    HwIntrinsics.AllowAll | HwIntrinsics.DisableFMA | HwIntrinsics.DisableAVX | HwIntrinsics.DisableHWIntrinsic);
+                    HwIntrinsics.AllowAll | HwIntrinsics.DisableFMA | HwIntrinsics.DisableAVX | HwIntrinsics.DisableSIMD);
             }
 
             // Forward transform
@@ -197,12 +197,12 @@ static void RunTest(string serialized)
                 // 4 paths:
                 // 1. AllowAll - call avx/fma implementation
                 // 2. DisableFMA - call avx without fma implementation
-                // 3. DisableAvx - call sse Vector4 implementation
-                // 4. DisableHWIntrinsic - call scalar fallback implementation
+                // 3. DisableAvx - call Vector4 implementation
+                // 4. DisableSIMD - call scalar fallback implementation
                 FeatureTestRunner.RunWithHwIntrinsicsFeature(
                     RunTest,
                     seed,
-                    HwIntrinsics.AllowAll | HwIntrinsics.DisableFMA | HwIntrinsics.DisableAVX | HwIntrinsics.DisableHWIntrinsic);
+                    HwIntrinsics.AllowAll | HwIntrinsics.DisableFMA | HwIntrinsics.DisableAVX | HwIntrinsics.DisableSIMD);
             }
         }
     }