Tests fix

tests/ImageSharp.Tests/Formats/Jpg/Block8x8FTests.cs

@@ -220,7 +220,7 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
 
                 // Reference implementation quantizes given block via division
                 Block8x8 expected = default;
-                ReferenceImplementations.Quantize(ref source, ref expected, ref quant, ZigZag.ZigZagOrder);
+                ReferenceImplementations.Quantize(ref source, ref expected, ref quant, ZigZag.TransposingOrder);
 
                 // Actual current implementation quantizes given block via multiplication
                 // With quantization table reciprocal

tests/ImageSharp.Tests/Formats/Jpg/DCTTests.cs

@@ -135,10 +135,9 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                     FastFloatingPointDCT.AdjustToIDCT(ref dequantMatrix);
                     srcBlock.MultiplyInPlace(ref dequantMatrix);
 
+                    // testee
                     // IDCT implementation tranforms blocks after transposition
                     srcBlock.TransposeInplace();
-
-                    // IDCT calculation
                     FastFloatingPointDCT.TransformIDCT(ref srcBlock);
 
                     float[] actualDest = srcBlock.ToArray();
@@ -180,7 +179,10 @@ namespace SixLabors.ImageSharp.Tests.Formats.Jpg
                     ReferenceImplementations.LLM_FloatingPoint_DCT.FDCT2D_llm(src, expectedDest, temp1, downscaleBy8: true);
 
                     // testee
+                    // Second transpose call is done by Quantize step
+                    // Do this manually here just to be complient to the reference implementation
                     FastFloatingPointDCT.TransformFDCT(ref block);
+                    block.TransposeInplace();
 
                     // Part of the IDCT calculations is fused into the quantization step
                     // We must multiply input block with adjusted no-quantization matrix