Add missing Bgra32 constructors

src/ImageSharp/PixelFormats/PixelImplementations/Bgra32.cs

@@ -73,6 +73,50 @@ public Bgra32(byte r, byte g, byte b, byte a)
         this.A = a;
     }
 
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Bgra32"/> struct from normalized components.
+    /// </summary>
+    /// <param name="r">The red component.</param>
+    /// <param name="g">The green component.</param>
+    /// <param name="b">The blue component.</param>
+    /// <param name="a">The alpha component.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public Bgra32(float r, float g, float b, float a = 1)
+        : this(new Vector4(r, g, b, a))
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Bgra32"/> struct from normalized RGB components with opaque alpha.
+    /// </summary>
+    /// <param name="vector">The red, green, and blue components.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public Bgra32(Vector3 vector)
+        : this(new Vector4(vector, 1F))
+    {
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Bgra32"/> struct from normalized RGBA components.
+    /// </summary>
+    /// <param name="vector">The red, green, blue, and alpha components.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public Bgra32(Vector4 vector)
+        : this() => this = Pack(vector);
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="Bgra32"/> struct from its packed representation.
+    /// </summary>
+    /// <remarks>
+    /// The bytes use B, G, R, A memory order. Integer interpretation follows the platform byte order.
+    /// On little-endian systems, the integer layout is <c>0xAARRGGBB</c>.
+    /// This constructor copies the stored bits without color conversion or alpha association.
+    /// </remarks>
+    /// <param name="packed">The packed component bits.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public Bgra32(uint packed)
+        : this() => this.PackedValue = packed;
+
     /// <summary>
     /// Gets or sets the packed representation of the Bgra32 struct.
     /// </summary>

tests/ImageSharp.Tests/PixelFormats/Bgra32Tests.cs

@@ -10,6 +10,44 @@ namespace SixLabors.ImageSharp.Tests.PixelFormats;
 [Trait("Category", "PixelFormats")]
 public class Bgra32Tests
 {
+    /// <summary>
+    /// Verifies that packed construction retains the stored bits and BGRA byte order.
+    /// </summary>
+    [Theory]
+    [InlineData(0U)]
+    [InlineData(uint.MaxValue)]
+    [InlineData(0xA1B2_C3D4U)]
+    public void Constructor_FromPackedValue(uint packed)
+    {
+        Bgra32 pixel = new(packed);
+        byte[] bytes = BitConverter.GetBytes(packed);
+
+        Assert.Equal(packed, pixel.PackedValue);
+        Assert.Equal(bytes[0], pixel.B);
+        Assert.Equal(bytes[1], pixel.G);
+        Assert.Equal(bytes[2], pixel.R);
+        Assert.Equal(bytes[3], pixel.A);
+    }
+
+    /// <summary>
+    /// Verifies normalized component and vector constructors, including bounds and implicit opaque alpha.
+    /// </summary>
+    [Theory]
+    [InlineData(1F, 0.1F, 0.133F, 0.5F, 255, 26, 34, 128)]
+    [InlineData(-1F, 2F, float.NaN, float.PositiveInfinity, 0, 255, 0, 255)]
+    public void Constructor_FromNormalizedComponents(float r, float g, float b, float a, byte expectedR, byte expectedG, byte expectedB, byte expectedA)
+    {
+        Bgra32 expected = new(expectedR, expectedG, expectedB, expectedA);
+
+        Assert.Equal(expected, new Bgra32(r, g, b, a));
+        Assert.Equal(expected, new Bgra32(new Vector4(r, g, b, a)));
+
+        expected.A = byte.MaxValue;
+
+        Assert.Equal(expected, new Bgra32(r, g, b));
+        Assert.Equal(expected, new Bgra32(new Vector3(r, g, b)));
+    }
+
     /// <summary>
     /// Tests the equality operators for equality.
     /// </summary>