ImageSharp/tests/ImageSharp.Benchmarks/Color/YcbCrToRgb.cs

// Copyright (c) Six Labors.
// Licensed under the Six Labors Split License.

using System.Numerics;
using BenchmarkDotNet.Attributes;

namespace SixLabors.ImageSharp.Benchmarks;

public class YcbCrToRgb
{
    [Benchmark(Baseline = true, Description = "Floating Point Conversion")]
    public Vector3 YcbCrToRgba()
    {
        const int y = 255;
        const int cb = 128;
        const int cr = 128;

        int ccb = cb - 128;
        int ccr = cr - 128;

        byte r = (byte)Numerics.Clamp(y + (1.402F * ccr), 0, 255);
        byte g = (byte)Numerics.Clamp(y - (0.34414F * ccb) - (0.71414F * ccr), 0, 255);
        byte b = (byte)Numerics.Clamp(y + (1.772F * ccb), 0, 255);

        return new Vector3(r, g, b);
    }

    [Benchmark(Description = "Scaled Integer Conversion")]
    public Vector3 YcbCrToRgbaScaled()
    {
        const int y = 255;
        const int cb = 128;
        const int cr = 128;

        int ccb = cb - 128;
        int ccr = cr - 128;

        // Scale by 1024, add .5F and truncate value
        int r0 = 1436 * ccr; // (1.402F * 1024) + .5F
        int g0 = 352 * ccb; // (0.34414F * 1024) + .5F
        int g1 = 731 * ccr; // (0.71414F  * 1024) + .5F
        int b0 = 1815 * ccb; // (1.772F * 1024) + .5F

        byte r = (byte)Numerics.Clamp(y + (r0 >> 10), 0, 255);
        byte g = (byte)Numerics.Clamp(y - (g0 >> 10) - (g1 >> 10), 0, 255);
        byte b = (byte)Numerics.Clamp(y + (b0 >> 10), 0, 255);

        return new Vector3(r, g, b);
    }
}