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Port YCbCr ColorConverter to ARM
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‎src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverter.YCbCrArm.cs‎

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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using System.Runtime.Intrinsics;
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using System.Runtime.Intrinsics.Arm;
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using System.Runtime.Intrinsics.X86;
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using static SixLabors.ImageSharp.SimdUtils;
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// ReSharper disable ImpureMethodCallOnReadonlyValueField
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namespace SixLabors.ImageSharp.Formats.Jpeg.Components;
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internal abstract partial class JpegColorConverterBase
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{
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internal sealed class YCbCrArm : JpegColorConverterArm
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{
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public YCbCrArm(int precision)
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: base(JpegColorSpace.YCbCr, precision)
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{
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}
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/// <inheritdoc/>
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public override void ConvertToRgbInplace(in ComponentValues values)
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{
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ref Vector128<float> c0Base =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component0));
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ref Vector128<float> c1Base =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component1));
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ref Vector128<float> c2Base =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component2));
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// Used for the color conversion
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var chromaOffset = Vector128.Create(-this.HalfValue);
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var scale = Vector128.Create(1 / this.MaximumValue);
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var rCrMult = Vector128.Create(YCbCrScalar.RCrMult);
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var gCbMult = Vector128.Create(-YCbCrScalar.GCbMult);
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var gCrMult = Vector128.Create(-YCbCrScalar.GCrMult);
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var bCbMult = Vector128.Create(YCbCrScalar.BCbMult);
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// Walking 8 elements at one step:
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nuint n = (uint)values.Component0.Length / (uint)Vector128<float>.Count;
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for (nuint i = 0; i < n; i++)
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{
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// y = yVals[i];
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// cb = cbVals[i] - 128F;
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// cr = crVals[i] - 128F;
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ref Vector128<float> c0 = ref Unsafe.Add(ref c0Base, i);
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ref Vector128<float> c1 = ref Unsafe.Add(ref c1Base, i);
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ref Vector128<float> c2 = ref Unsafe.Add(ref c2Base, i);
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Vector128<float> y = c0;
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Vector128<float> cb = AdvSimd.Add(c1, chromaOffset);
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Vector128<float> cr = AdvSimd.Add(c2, chromaOffset);
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// r = y + (1.402F * cr);
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// g = y - (0.344136F * cb) - (0.714136F * cr);
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// b = y + (1.772F * cb);
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Vector128<float> r = HwIntrinsics.MultiplyAdd(y, cr, rCrMult);
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Vector128<float> g = HwIntrinsics.MultiplyAdd(HwIntrinsics.MultiplyAdd(y, cb, gCbMult), cr, gCrMult);
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Vector128<float> b = HwIntrinsics.MultiplyAdd(y, cb, bCbMult);
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r = AdvSimd.Multiply(AdvSimd.RoundToNearest(r), scale);
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g = AdvSimd.Multiply(AdvSimd.RoundToNearest(g), scale);
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b = AdvSimd.Multiply(AdvSimd.RoundToNearest(b), scale);
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c0 = r;
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c1 = g;
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c2 = b;
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}
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}
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/// <inheritdoc/>
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public override void ConvertFromRgb(in ComponentValues values, Span<float> rLane, Span<float> gLane, Span<float> bLane)
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{
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ref Vector128<float> destY =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component0));
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ref Vector128<float> destCb =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component1));
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ref Vector128<float> destCr =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(values.Component2));
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ref Vector128<float> srcR =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(rLane));
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ref Vector128<float> srcG =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(gLane));
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ref Vector128<float> srcB =
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ref Unsafe.As<float, Vector128<float>>(ref MemoryMarshal.GetReference(bLane));
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// Used for the color conversion
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var chromaOffset = Vector128.Create(this.HalfValue);
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var f0299 = Vector128.Create(0.299f);
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var f0587 = Vector128.Create(0.587f);
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var f0114 = Vector128.Create(0.114f);
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var fn0168736 = Vector128.Create(-0.168736f);
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var fn0331264 = Vector128.Create(-0.331264f);
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var fn0418688 = Vector128.Create(-0.418688f);
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var fn0081312F = Vector128.Create(-0.081312F);
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var f05 = Vector128.Create(0.5f);
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nuint n = (uint)values.Component0.Length / (uint)Vector128<float>.Count;
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for (nuint i = 0; i < n; i++)
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{
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Vector128<float> r = Unsafe.Add(ref srcR, i);
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Vector128<float> g = Unsafe.Add(ref srcG, i);
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Vector128<float> b = Unsafe.Add(ref srcB, i);
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// y = 0 + (0.299 * r) + (0.587 * g) + (0.114 * b)
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// cb = 128 - (0.168736 * r) - (0.331264 * g) + (0.5 * b)
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// cr = 128 + (0.5 * r) - (0.418688 * g) - (0.081312 * b)
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Vector128<float> y = HwIntrinsics.MultiplyAdd(HwIntrinsics.MultiplyAdd(AdvSimd.Multiply(f0114, b), f0587, g), f0299, r);
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Vector128<float> cb = AdvSimd.Add(chromaOffset, HwIntrinsics.MultiplyAdd(HwIntrinsics.MultiplyAdd(AdvSimd.Multiply(f05, b), fn0331264, g), fn0168736, r));
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Vector128<float> cr = AdvSimd.Add(chromaOffset, HwIntrinsics.MultiplyAdd(HwIntrinsics.MultiplyAdd(AdvSimd.Multiply(fn0081312F, b), fn0418688, g), f05, r));
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Unsafe.Add(ref destY, i) = y;
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Unsafe.Add(ref destCb, i) = cb;
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Unsafe.Add(ref destCr, i) = cr;
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}
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}
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}
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}

‎src/ImageSharp/Formats/Jpeg/Components/ColorConverters/JpegColorConverterBase.cs‎

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@@ -138,6 +138,11 @@ private static JpegColorConverterBase GetYCbCrConverter(int precision)
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return new YCbCrAvx(precision);
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}
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if (JpegColorConverterArm.IsSupported)
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{
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return new YCbCrArm(precision);
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}
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if (JpegColorConverterVector.IsSupported)
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{
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return new YCbCrVector(precision);

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

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new JpegColorConverterBase.YCbCrScalar(8),
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precísion: 2);
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[Theory]
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[MemberData(nameof(Seeds))]
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public void FromYCbCrArm(int seed) =>
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this.TestConversionToRgb(new JpegColorConverterBase.YCbCrArm(8),
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3,
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seed,
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new JpegColorConverterBase.YCbCrScalar(8));
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[Theory]
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[MemberData(nameof(Seeds))]
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public void FromRgbToYCbCrArm(int seed) =>
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this.TestConversionFromRgb(new JpegColorConverterBase.YCbCrArm(8),
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3,
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seed,
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new JpegColorConverterBase.YCbCrScalar(8),
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precísion: 2);
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[Theory]
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[MemberData(nameof(Seeds))]
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public void FromCmykAvx2(int seed) =>

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