ImageSharp/src/ImageSharp/PixelFormats/PixelImplementations/L8.cs

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

using System.Numerics;
using System.Runtime.CompilerServices;

namespace SixLabors.ImageSharp.PixelFormats;

/// <summary>
/// Packed pixel type containing a single 8-bit normalized luminance value.
/// <para>
/// Ranges from [0, 0, 0, 1] to [1, 1, 1, 1] in vector form.
/// </para>
/// </summary>
public partial struct L8 : IPixel<L8>, IPackedVector<byte>
{
    private static readonly Vector4 MaxBytes = new(255F);
    private static readonly Vector4 Half = new(0.5F);

    /// <summary>
    /// Initializes a new instance of the <see cref="L8"/> struct.
    /// </summary>
    /// <param name="luminance">The luminance component.</param>
    public L8(byte luminance) => this.PackedValue = luminance;

    /// <inheritdoc />
    public byte PackedValue { get; set; }

    /// <summary>
    /// Compares two <see cref="L8"/> objects for equality.
    /// </summary>
    /// <param name="left">The <see cref="L8"/> on the left side of the operand.</param>
    /// <param name="right">The <see cref="L8"/> on the right side of the operand.</param>
    /// <returns>
    /// True if the <paramref name="left"/> parameter is equal to the <paramref name="right"/> parameter; otherwise, false.
    /// </returns>
    [MethodImpl(InliningOptions.ShortMethod)]
    public static bool operator ==(L8 left, L8 right) => left.Equals(right);

    /// <summary>
    /// Compares two <see cref="L8"/> objects for equality.
    /// </summary>
    /// <param name="left">The <see cref="L8"/> on the left side of the operand.</param>
    /// <param name="right">The <see cref="L8"/> on the right side of the operand.</param>
    /// <returns>
    /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter; otherwise, false.
    /// </returns>
    [MethodImpl(InliningOptions.ShortMethod)]
    public static bool operator !=(L8 left, L8 right) => !left.Equals(right);

    /// <inheritdoc />
    public static PixelTypeInfo GetPixelTypeInfo() => PixelTypeInfo.Create<L8>(PixelComponentInfo.Create<L8>(1, 8), PixelAlphaRepresentation.None);

    /// <inheritdoc />
    public readonly PixelOperations<L8> CreatePixelOperations() => new PixelOperations();

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromScaledVector4(Vector4 vector) => this.ConvertFromRgbaScaledVector4(vector);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public readonly Vector4 ToScaledVector4() => this.ToVector4();

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromVector4(Vector4 vector) => this.ConvertFromRgbaScaledVector4(vector);

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public readonly Vector4 ToVector4()
    {
        float rgb = this.PackedValue / 255F;
        return new Vector4(rgb, rgb, rgb, 1F);
    }

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromArgb32(Argb32 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromBgr24(Bgr24 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromBgra32(Bgra32 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromAbgr32(Abgr32 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromBgra5551(Bgra5551 source) => this.FromScaledVector4(source.ToScaledVector4());

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromL8(L8 source) => this = source;

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromL16(L16 source) => this.PackedValue = ColorNumerics.DownScaleFrom16BitTo8Bit(source.PackedValue);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromLa16(La16 source) => this.PackedValue = source.L;

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromLa32(La32 source) => this.PackedValue = ColorNumerics.DownScaleFrom16BitTo8Bit(source.L);

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromRgb24(Rgb24 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromRgba32(Rgba32 source) => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(source.R, source.G, source.B);

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public void ToRgba32(ref Rgba32 dest)
    {
        dest.R = this.PackedValue;
        dest.G = this.PackedValue;
        dest.B = this.PackedValue;
        dest.A = byte.MaxValue;
    }

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromRgb48(Rgb48 source)
        => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.R),
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.G),
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.B));

    /// <inheritdoc/>
    [MethodImpl(InliningOptions.ShortMethod)]
    public void FromRgba64(Rgba64 source)
        => this.PackedValue = ColorNumerics.Get8BitBT709Luminance(
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.R),
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.G),
            ColorNumerics.DownScaleFrom16BitTo8Bit(source.B));

    /// <inheritdoc />
    public override readonly bool Equals(object? obj) => obj is L8 other && this.Equals(other);

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public readonly bool Equals(L8 other) => this.PackedValue.Equals(other.PackedValue);

    /// <inheritdoc />
    public override readonly string ToString() => $"L8({this.PackedValue})";

    /// <inheritdoc />
    [MethodImpl(InliningOptions.ShortMethod)]
    public override readonly int GetHashCode() => this.PackedValue.GetHashCode();

    [MethodImpl(InliningOptions.ShortMethod)]
    internal void ConvertFromRgbaScaledVector4(Vector4 vector)
    {
        vector *= MaxBytes;
        vector += Half;
        vector = Numerics.Clamp(vector, Vector4.Zero, MaxBytes);
        this.PackedValue = ColorNumerics.Get8BitBT709Luminance((byte)vector.X, (byte)vector.Y, (byte)vector.Z);
    }
}