Simplified RgbToYCbCrConverterVectorized.Convert() method

src/ImageSharp/Formats/Jpeg/Components/Encoder/RgbToYCbCrConverterVectorized.cs

@@ -34,12 +34,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             3, 0, 0, 0, 4, 0, 0, 0, 5, 0, 0, 0, 7, 0, 0, 0
         };
 
-        private static ReadOnlySpan<byte> MoveLast24BytesToSeparateLanes => new byte[]
-        {
-            2, 0, 0, 0, 3, 0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0,
-            5, 0, 0, 0, 6, 0, 0, 0, 7, 0, 0, 0, 1, 0, 0, 0
-        };
-
         private static ReadOnlySpan<byte> ExtractRgb => new byte[]
         {
             0, 3, 6, 9, 1, 4, 7, 10, 2, 5, 8, 11, 0xFF, 0xFF, 0xFF, 0xFF,
@@ -102,7 +96,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
             // Extra mask & separate stride:7 calculations can be eliminated by simply providing rgb pixel span of slightly bigger size than pixels data need:
             // Total pixel data size is 192 bytes, avx registers need it to be 200 bytes
             const int bytesPerRgbStride = 24;
-            for (int i = 0; i < 7; i++)
+            for (int i = 0; i < 8; i++)
             {
                 rgb = Avx2.PermuteVar8x32(Unsafe.AddByteOffset(ref rgbByteSpan, (IntPtr)(bytesPerRgbStride * i)).AsUInt32(), extractToLanesMask).AsByte();
 
@@ -124,26 +118,6 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
                 // 128F + ((0.5F * r) - (0.418688F * g) - (0.081312F * b))
                 Unsafe.Add(ref destCrRef, i) = Avx.Add(f128, SimdUtils.HwIntrinsics.MultiplyAdd(SimdUtils.HwIntrinsics.MultiplyAdd(Avx.Multiply(fn0081312F, b), fn0418688, g), f05, r));
             }
-
-            extractToLanesMask = Unsafe.As<byte, Vector256<uint>>(ref MemoryMarshal.GetReference(MoveLast24BytesToSeparateLanes));
-            rgb = Avx2.PermuteVar8x32(Unsafe.AddByteOffset(ref rgbByteSpan, (IntPtr)160).AsUInt32(), extractToLanesMask).AsByte();
-            rgb = Avx2.Shuffle(rgb, extractRgbMask);
-
-            rg = Avx2.UnpackLow(rgb, zero);
-            bx = Avx2.UnpackHigh(rgb, zero);
-
-            r = Avx.ConvertToVector256Single(Avx2.UnpackLow(rg, zero).AsInt32());
-            g = Avx.ConvertToVector256Single(Avx2.UnpackHigh(rg, zero).AsInt32());
-            b = Avx.ConvertToVector256Single(Avx2.UnpackLow(bx, zero).AsInt32());
-
-            // (0.299F * r) + (0.587F * g) + (0.114F * b);
-            Unsafe.Add(ref destYRef, 7) = SimdUtils.HwIntrinsics.MultiplyAdd(SimdUtils.HwIntrinsics.MultiplyAdd(Avx.Multiply(f0114, b), f0587, g), f0299, r);
-
-            // 128F + ((-0.168736F * r) - (0.331264F * g) + (0.5F * b))
-            Unsafe.Add(ref destCbRef, 7) = Avx.Add(f128, SimdUtils.HwIntrinsics.MultiplyAdd(SimdUtils.HwIntrinsics.MultiplyAdd(Avx.Multiply(f05, b), fn0331264, g), fn0168736, r));
-
-            // 128F + ((0.5F * r) - (0.418688F * g) - (0.081312F * b))
-            Unsafe.Add(ref destCrRef, 7) = Avx.Add(f128, SimdUtils.HwIntrinsics.MultiplyAdd(SimdUtils.HwIntrinsics.MultiplyAdd(Avx.Multiply(fn0081312F, b), fn0418688, g), f05, r));
 #endif
         }
     }

src/ImageSharp/Formats/Jpeg/Components/Encoder/YCbCrForwardConverter{TPixel}.cs

@@ -2,6 +2,7 @@
 // Licensed under the Apache License, Version 2.0.
 
 using System;
+using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
 using SixLabors.ImageSharp.PixelFormats;
 
@@ -42,14 +43,19 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
         /// <summary>
         /// Temporal RGB block
         /// </summary>
-        private GenericBlock8x8<Rgb24> rgbBlock;
+        private Span<Rgb24> rgbSpan;
 
         public static YCbCrForwardConverter<TPixel> Create()
         {
             var result = default(YCbCrForwardConverter<TPixel>);
+
+            // creating rgb pixel bufferr
+            // TODO: this is subject to discuss
+            result.rgbSpan = MemoryMarshal.Cast<byte, Rgb24>(new byte[200].AsSpan());
+
+            // Avoid creating lookup tables, when vectorized converter is supported
             if (!RgbToYCbCrConverterVectorized.IsSupported)
             {
-                // Avoid creating lookup tables, when vectorized converter is supported
                 result.colorTables = RgbToYCbCrConverterLut.Create();
             }
 
@@ -63,8 +69,7 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
         {
             this.pixelBlock.LoadAndStretchEdges(frame.PixelBuffer, x, y, ref currentRows);
 
-            Span<Rgb24> rgbSpan = this.rgbBlock.AsSpanUnsafe();
-            PixelOperations<TPixel>.Instance.ToRgb24(frame.GetConfiguration(), this.pixelBlock.AsSpanUnsafe(), rgbSpan);
+            PixelOperations<TPixel>.Instance.ToRgb24(frame.GetConfiguration(), this.pixelBlock.AsSpanUnsafe(), this.rgbSpan);
 
             ref Block8x8F yBlock = ref this.Y;
             ref Block8x8F cbBlock = ref this.Cb;
@@ -72,11 +77,11 @@ namespace SixLabors.ImageSharp.Formats.Jpeg.Components.Encoder
 
             if (RgbToYCbCrConverterVectorized.IsSupported)
             {
-                RgbToYCbCrConverterVectorized.Convert(rgbSpan, ref yBlock, ref cbBlock, ref crBlock);
+                RgbToYCbCrConverterVectorized.Convert(this.rgbSpan, ref yBlock, ref cbBlock, ref crBlock);
             }
             else
             {
-                this.colorTables.Convert(rgbSpan, ref yBlock, ref cbBlock, ref crBlock);
+                this.colorTables.Convert(this.rgbSpan, ref yBlock, ref cbBlock, ref crBlock);
             }
         }
     }