ImageSharp/tests/ImageSharp.Benchmarks/Color/RgbToYCbCr.cs

namespace ImageSharp.Benchmarks
{
    using System.Numerics;

    using BenchmarkDotNet.Attributes;

    public partial class RgbToYCbCr
    {
        private static readonly Vector3 VectorY = new Vector3(0.299F, 0.587F, 0.114F);
        private static readonly Vector3 VectorCb = new Vector3(-0.168736F, 0.331264F, 0.5F);
        private static readonly Vector3 VectorCr = new Vector3(0.5F, 0.418688F, 0.081312F);

        [Benchmark(Baseline = true, Description = "Floating Point Conversion")]
        public Vector3 RgbaToYcbCr()
        {
            Vector3 v = new Vector3(255);

            float yy = (0.299F * v.X) + (0.587F * v.Y) + (0.114F * v.Z);
            float cb = 128 + ((-0.168736F * v.X) - (0.331264F * v.Y) + (0.5F * v.Z));
            float cr = 128 + ((0.5F * v.X) - (0.418688F * v.Y) - (0.081312F * v.Z));

            return new Vector3(yy, cb, cr);
        }

        [Benchmark(Description = "Simd Floating Point Conversion")]
        public Vector3 RgbaToYcbCrSimd()
        {
            Vector3 vectorRgb = new Vector3(255);
            Vector3 vectorY = VectorY * vectorRgb;
            Vector3 vectorCb = VectorCb * vectorRgb;
            Vector3 vectorCr = VectorCr * vectorRgb;

            float yy = vectorY.X + vectorY.Y + vectorY.Z;
            float cb = 128 + (vectorCb.X - vectorCb.Y + vectorCb.Z);
            float cr = 128 + (vectorCr.X - vectorCr.Y - vectorCr.Z);

            return new Vector3(yy, cb, cr);
        }

        [Benchmark(Description = "Scaled Integer Conversion")]
        public Vector3 RgbaToYcbCrScaled()
        {
            int r = 255;
            int g = 255;
            int b = 255;

            // Scale by 1024, add .5F and truncate value
            int y0 = 306 * r; // (0.299F * 1024) + .5F
            int y1 = 601 * g; // (0.587F * 1024) + .5F
            int y2 = 117 * b; // (0.114F * 1024) + .5F

            int cb0 = -172 * r; // (-0.168736F * 1024) + .5F
            int cb1 = 339 * g; // (0.331264F * 1024) + .5F
            int cb2 = 512 * b; // (0.5F * 1024) + .5F

            int cr0 = 512 * r; // (0.5F * 1024) + .5F
            int cr1 = 429 * g; // (0.418688F * 1024) + .5F
            int cr2 = 83 * b; // (0.081312F * 1024) + .5F

            float yy = (y0 + y1 + y2) >> 10;
            float cb = 128 + ((cb0 - cb1 + cb2) >> 10);
            float cr = 128 + ((cr0 - cr1 - cr2) >> 10);

            return new Vector3(yy, cb, cr);
        }

        [Benchmark(Description = "Scaled Integer LUT Conversion")]
        public Vector3 RgbaToYcbCrScaledLut()
        {
            int r = 255;
            int g = 255;
            int b = 255;

            float yy = (LookupTables.Y0[r] + LookupTables.Y1[g] + LookupTables.Y2[b]) >> 10;
            float cb = 128 + ((LookupTables.Cb0[r] - LookupTables.Cb1[g] + LookupTables.Cb2Cr0[b]) >> 10);
            float cr = 128 + ((LookupTables.Cb2Cr0[r] - LookupTables.Cr1[g] - LookupTables.Cr2[b]) >> 10);

            return new Vector3(yy, cb, cr);
        }
    }
}