Add Bgr565

src/ImageSharp/Colors/Color.cs

@@ -219,7 +219,7 @@ namespace ImageSharp
         /// <param name="left">The <see cref="Color"/> on the left side of the operand.</param>
         /// <param name="right">The <see cref="Color"/> 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.
+        /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter; otherwise, false.
         /// </returns>
         public static bool operator !=(Color left, Color right)
         {

src/ImageSharp/Colors/PackedPixel/Alpha8.cs

@@ -50,7 +50,7 @@ namespace ImageSharp
         /// <param name="left">The <see cref="Alpha8"/> on the left side of the operand.</param>
         /// <param name="right">The <see cref="Alpha8"/> 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.
+        /// True if the <paramref name="left"/> parameter is not equal to the <paramref name="right"/> parameter; otherwise, false.
         /// </returns>
         public static bool operator !=(Alpha8 left, Alpha8 right)
         {

src/ImageSharp/Colors/PackedPixel/Bgr565.cs

@@ -0,0 +1,171 @@
+// <copyright file="Bgr565.cs" company="James Jackson-South">
+// Copyright (c) James Jackson-South and contributors.
+// Licensed under the Apache License, Version 2.0.
+// </copyright>
+
+namespace ImageSharp
+{
+    using System;
+    using System.Numerics;
+
+    /// <summary>
+    /// Packed vector type containing unsigned normalized values ranging from 0 to 1. 
+    /// The x and z components use 5 bits, and the y component uses 6 bits.
+    /// </summary>
+    public struct Bgr565 : IPackedPixel<ushort>, IEquatable<Bgr565>
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Bgr565"/> struct. 
+        /// </summary>
+        /// <param name="x">The x-component</param>
+        /// <param name="y">The y-component</param>
+        /// <param name="z">The z-component</param>
+        public Bgr565(float x, float y, float z)
+        {
+            this.PackedValue = Pack(x, y, z);
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Bgr565"/> struct. 
+        /// </summary>
+        /// <param name="vector">
+        /// The vector containing the components for the packed value.
+        /// </param>
+        public Bgr565(Vector3 vector)
+        {
+            this.PackedValue = Pack(vector.X, vector.Y, vector.Z);
+        }
+
+        /// <inheritdoc />
+        public ushort PackedValue { get; set; }
+
+        /// <summary>
+        /// Compares two <see cref="Bgr565"/> objects for equality.
+        /// </summary>
+        /// <param name="left">The <see cref="Bgr565"/> on the left side of the operand.</param>
+        /// <param name="right">The <see cref="Bgr565"/> 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>
+        public static bool operator ==(Bgr565 left, Bgr565 right)
+        {
+            return left.PackedValue == right.PackedValue;
+        }
+
+        /// <summary>
+        /// Compares two <see cref="Bgr565"/> objects for equality.
+        /// </summary>
+        /// <param name="left">The <see cref="Bgr565"/> on the left side of the operand.</param>
+        /// <param name="right">The <see cref="Bgr565"/> 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>
+        public static bool operator !=(Bgr565 left, Bgr565 right)
+        {
+            return left.PackedValue != right.PackedValue;
+        }
+
+        /// <summary>
+        /// Expands the packed representation into a <see cref="Vector3"/>.
+        /// The vector components are typically expanded in least to greatest significance order.
+        /// </summary>
+        /// <returns>The <see cref="Vector3"/>.</returns>
+        public Vector3 ToVector3()
+        {
+            return new Vector3(
+                       ((this.PackedValue >> 11) & 0x1F) * (1F / 31F),
+                       ((this.PackedValue >> 5) & 0x3F) * (1F / 63F),
+                       (this.PackedValue & 0x1F) * (1F / 31F));
+        }
+
+        /// <inheritdoc />
+        public void PackFromVector4(Vector4 vector)
+        {
+            this.PackedValue = Pack(vector.X, vector.Y, vector.Z);
+        }
+
+        /// <inheritdoc />
+        public Vector4 ToVector4()
+        {
+            return new Vector4(this.ToVector3(), 1F);
+        }
+
+        /// <inheritdoc />
+        public void PackFromBytes(byte x, byte y, byte z, byte w)
+        {
+            this.PackFromVector4(new Vector4(x, y, z, w) / 255F);
+        }
+
+        /// <inheritdoc />
+        public void ToBytes(byte[] bytes, int startIndex, ComponentOrder componentOrder)
+        {
+            Vector4 vector = this.ToVector4() * 255F;
+
+            switch (componentOrder)
+            {
+                case ComponentOrder.ZYX:
+                    bytes[startIndex] = (byte)vector.Z;
+                    bytes[startIndex + 1] = (byte)vector.Y;
+                    bytes[startIndex + 2] = (byte)vector.X;
+                    break;
+                case ComponentOrder.ZYXW:
+                    bytes[startIndex] = (byte)vector.Z;
+                    bytes[startIndex + 1] = (byte)vector.Y;
+                    bytes[startIndex + 2] = (byte)vector.X;
+                    bytes[startIndex + 3] = (byte)vector.W;
+                    break;
+                case ComponentOrder.XYZ:
+                    bytes[startIndex] = (byte)vector.X;
+                    bytes[startIndex + 1] = (byte)vector.Y;
+                    bytes[startIndex + 2] = (byte)vector.Z;
+                    break;
+                case ComponentOrder.XYZW:
+                    bytes[startIndex] = (byte)vector.X;
+                    bytes[startIndex + 1] = (byte)vector.Y;
+                    bytes[startIndex + 2] = (byte)vector.Z;
+                    bytes[startIndex + 3] = (byte)vector.W;
+                    break;
+                default:
+                    throw new NotSupportedException();
+            }
+        }
+
+        /// <inheritdoc />
+        public override bool Equals(object obj)
+        {
+            return (obj is Bgr565) && this.Equals((Bgr565)obj);
+        }
+
+        /// <inheritdoc />
+        public bool Equals(Bgr565 other)
+        {
+            return this.PackedValue == other.PackedValue;
+        }
+
+        /// <inheritdoc />
+        public override string ToString()
+        {
+            return this.ToVector3().ToString();
+        }
+
+        /// <inheritdoc />
+        public override int GetHashCode()
+        {
+            return this.PackedValue.GetHashCode();
+        }
+
+        /// <summary>
+        /// Packs a <see cref="float"/> components into a <see cref="ushort"/>.
+        /// </summary>
+        /// <param name="x">The x-component</param>
+        /// <param name="y">The y-component</param>
+        /// <param name="z">The z-component</param>
+        /// <returns>The <see cref="ushort"/> containing the packed values.</returns>
+        private static ushort Pack(float x, float y, float z)
+        {
+            return (ushort)((((int)Math.Round(x.Clamp(0, 1) * 31F) & 0x1F) << 11) |
+                   (((int)Math.Round(y.Clamp(0, 1) * 63F) & 0x3F) << 5) |
+                   ((int)Math.Round(z.Clamp(0, 1) * 31F) & 0x1F));
+        }
+    }
+}

src/ImageSharp/Colors/PackedPixel/README.md

@@ -0,0 +1,3 @@
+Pixel formats adapted and extended from:
+
+https://github.com/MonoGame/MonoGame

tests/ImageSharp.Tests/Colors/PackedVectorTests.cs

@@ -5,6 +5,7 @@
 
 namespace ImageSharp.Tests.Colors
 {
+    using System;
     using System.Numerics;
 
     using Xunit;
@@ -31,6 +32,7 @@ namespace ImageSharp.Tests.Colors
 
             // Test ordering
             Vector4 vector = new Alpha8(.5F).ToVector4();
+
             Assert.Equal(vector.X, 0);
             Assert.Equal(vector.Y, 0);
             Assert.Equal(vector.Z, 0);
@@ -53,5 +55,72 @@ namespace ImageSharp.Tests.Colors
             new Alpha8(.5F).ToBytes(rgb, 0, ComponentOrder.ZYXW);
             Assert.Equal(bgra, new byte[] { 0, 0, 0, 128 });
         }
+
+        [Fact]
+        public void Bgr565()
+        {
+            // Test the limits.
+            Assert.Equal(0x0, new Bgr565(Vector3.Zero).PackedValue);
+            Assert.Equal(0xFFFF, new Bgr565(Vector3.One).PackedValue);
+
+            // Test ToVector3.
+            Assert.True(Equal(Vector3.One, new Bgr565(Vector3.One).ToVector3()));
+            Assert.True(Equal(Vector3.Zero, new Bgr565(Vector3.Zero).ToVector3()));
+            Assert.True(Equal(Vector3.UnitX, new Bgr565(Vector3.UnitX).ToVector3()));
+            Assert.True(Equal(Vector3.UnitY, new Bgr565(Vector3.UnitY).ToVector3()));
+            Assert.True(Equal(Vector3.UnitZ, new Bgr565(Vector3.UnitZ).ToVector3()));
+
+            // Test clamping.
+            Assert.True(Equal(Vector3.Zero, new Bgr565(Vector3.One * -1234F).ToVector3()));
+            Assert.True(Equal(Vector3.One, new Bgr565(Vector3.One * 1234F).ToVector3()));
+
+            // Make sure the swizzle is correct.
+            Assert.Equal(0xF800, new Bgr565(Vector3.UnitX).PackedValue);
+            Assert.Equal(0x07E0, new Bgr565(Vector3.UnitY).PackedValue);
+            Assert.Equal(0x001F, new Bgr565(Vector3.UnitZ).PackedValue);
+
+            float x = 0.1F;
+            float y = -0.3F;
+            float z = 0.5F;
+            Assert.Equal(6160, new Bgr565(x, y, z).PackedValue);
+
+            byte[] rgb = new byte[3];
+            byte[] rgba = new byte[4];
+            byte[] bgr = new byte[3];
+            byte[] bgra = new byte[4];
+
+            new Bgr565(x, y, z).ToBytes(rgb, 0, ComponentOrder.XYZ);
+            Assert.Equal(rgb, new byte[] { 24, 0, 131 });
+
+            new Bgr565(x, y, z).ToBytes(rgba, 0, ComponentOrder.XYZW);
+            Assert.Equal(rgba, new byte[] { 24, 0, 131, 255 });
+
+            new Bgr565(x, y, z).ToBytes(bgr, 0, ComponentOrder.ZYX);
+            Assert.Equal(bgr, new byte[] { 131, 0, 24 });
+
+            new Bgr565(x, y, z).ToBytes(bgra, 0, ComponentOrder.ZYXW);
+            Assert.Equal(bgra, new byte[] { 131, 0, 24, 255 });
+        }
+
+        // Comparison helpers with small tolerance to allow for floating point rounding during computations.
+        public static bool Equal(float a, float b)
+        {
+            return Math.Abs(a - b) < 1e-5;
+        }
+
+        public static bool Equal(Vector2 a, Vector2 b)
+        {
+            return Equal(a.X, b.X) && Equal(a.Y, b.Y);
+        }
+
+        public static bool Equal(Vector3 a, Vector3 b)
+        {
+            return Equal(a.X, b.X) && Equal(a.Y, b.Y) && Equal(a.Z, b.Z);
+        }
+
+        public static bool Equal(Vector4 a, Vector4 b)
+        {
+            return Equal(a.X, b.X) && Equal(a.Y, b.Y) && Equal(a.Z, b.Z) && Equal(a.W, b.W);
+        }
     }
 }