Basic La16 implementation

src/ImageSharp/PixelFormats/PixelImplementations/L16.cs

@@ -7,7 +7,7 @@ using System.Runtime.CompilerServices;
 namespace SixLabors.ImageSharp.PixelFormats
 {
     /// <summary>
-    /// Packed pixel type containing a single 16 bit normalized luminance value.
+    /// Packed pixel type containing a single 16-bit normalized luminance value.
     /// <para>
     /// Ranges from [0, 0, 0, 1] to [1, 1, 1, 1] in vector form.
     /// </para>

src/ImageSharp/PixelFormats/PixelImplementations/L8.cs

@@ -7,7 +7,7 @@ using System.Runtime.CompilerServices;
 namespace SixLabors.ImageSharp.PixelFormats
 {
     /// <summary>
-    /// Packed pixel type containing a single 8 bit normalized luminance value.
+    /// 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>

src/ImageSharp/PixelFormats/PixelImplementations/La16.cs

@@ -0,0 +1,216 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Numerics;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace SixLabors.ImageSharp.PixelFormats
+{
+    /// <summary>
+    /// Packed pixel type containing two 8-bit normalized values representing luminance and alpha.
+    /// <para>
+    /// Ranges from [0, 0, 0, 0] to [1, 1, 1, 1] in vector form.
+    /// </para>
+    /// </summary>
+    [StructLayout(LayoutKind.Explicit)]
+    public struct La16 : IPixel<La16>, IPackedVector<ushort>
+    {
+        private static readonly Vector4 MaxBytes = new Vector4(255F);
+        private static readonly Vector4 Half = new Vector4(0.5F);
+
+        /// <summary>
+        /// Gets or sets the luminance component.
+        /// </summary>
+        [FieldOffset(0)]
+        public byte L;
+
+        /// <summary>
+        /// Gets or sets the alpha component.
+        /// </summary>
+        [FieldOffset(1)]
+        public byte A;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="La16"/> struct.
+        /// </summary>
+        /// <param name="l">The luminance component.</param>
+        /// <param name="a">The alpha componant.</param>
+        public La16(byte l, byte a)
+        {
+            this.L = l;
+            this.A = a;
+        }
+
+        /// <inheritdoc/>
+        public ushort PackedValue
+        {
+            get => Unsafe.As<La16, ushort>(ref this);
+
+            set => Unsafe.As<La16, ushort>(ref this) = value;
+        }
+
+        /// <summary>
+        /// Compares two <see cref="La16"/> objects for equality.
+        /// </summary>
+        /// <param name="left">The <see cref="La16"/> on the left side of the operand.</param>
+        /// <param name="right">The <see cref="La16"/> 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 ==(La16 left, La16 right) => left.Equals(right);
+
+        /// <summary>
+        /// Compares two <see cref="La16"/> objects for equality.
+        /// </summary>
+        /// <param name="left">The <see cref="La16"/> on the left side of the operand.</param>
+        /// <param name="right">The <see cref="La16"/> 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 !=(La16 left, La16 right) => !left.Equals(right);
+
+        /// <inheritdoc/>
+        public PixelOperations<La16> CreatePixelOperations() => new PixelOperations<La16>();
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public bool Equals(La16 other) => this.PackedValue.Equals(other.PackedValue);
+
+        /// <inheritdoc />
+        public override bool Equals(object obj) => obj is La16 other && this.Equals(other);
+
+        /// <inheritdoc />
+        public override string ToString() => $"La16({this.L}, {this.A})";
+
+        /// <inheritdoc />
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public override int GetHashCode() => this.PackedValue.GetHashCode();
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromArgb32(Argb32 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(source.R, source.G, source.B);
+            this.A = source.A;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromBgr24(Bgr24 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(source.R, source.G, source.B);
+            this.A = byte.MaxValue;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromBgra32(Bgra32 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(source.R, source.G, source.B);
+            this.A = source.A;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromBgra5551(Bgra5551 source) => this.FromScaledVector4(source.ToScaledVector4());
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromL16(L16 source)
+        {
+            this.L = ImageMaths.DownScaleFrom16BitTo8Bit(source.PackedValue);
+            this.A = byte.MaxValue;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromL8(L8 source)
+        {
+            this.L = source.PackedValue;
+            this.A = byte.MaxValue;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromRgb24(Rgb24 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(source.R, source.G, source.B);
+            this.A = byte.MaxValue;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromRgb48(Rgb48 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.R),
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.G),
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.B));
+
+            this.A = byte.MaxValue;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromRgba32(Rgba32 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(source.R, source.G, source.B);
+            this.A = source.A;
+        }
+
+        /// <inheritdoc/>
+        public void FromRgba64(Rgba64 source)
+        {
+            this.L = ImageMaths.Get8BitBT709Luminance(
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.R),
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.G),
+                ImageMaths.DownScaleFrom16BitTo8Bit(source.B));
+
+            this.A = ImageMaths.DownScaleFrom16BitTo8Bit(source.A);
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromScaledVector4(Vector4 vector) => this.ConvertFromRgbaScaledVector4(vector);
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void FromVector4(Vector4 vector) => this.ConvertFromRgbaScaledVector4(vector);
+
+        /// <inheritdoc />
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public void ToRgba32(ref Rgba32 dest)
+        {
+            dest.R = this.L;
+            dest.G = this.L;
+            dest.B = this.L;
+            dest.A = this.A;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public Vector4 ToScaledVector4() => this.ToVector4();
+
+        /// <inheritdoc/>
+        [MethodImpl(InliningOptions.ShortMethod)]
+        public Vector4 ToVector4()
+        {
+            const float Max = 255F;
+            float rgb = this.L / Max;
+            return new Vector4(rgb, rgb, rgb, this.A / Max);
+        }
+
+        [MethodImpl(InliningOptions.ShortMethod)]
+        internal void ConvertFromRgbaScaledVector4(Vector4 vector)
+        {
+            vector *= MaxBytes;
+            vector += Half;
+            vector = Vector4.Clamp(vector, Vector4.Zero, MaxBytes);
+            this.L = ImageMaths.Get8BitBT709Luminance((byte)vector.X, (byte)vector.Y, (byte)vector.Z);
+            this.A = (byte)vector.W;
+        }
+    }
+}