diff --git a/src/ImageSharp/Common/Helpers/ImageMaths.cs b/src/ImageSharp/Common/Helpers/ImageMaths.cs
index 6c52eded5..402aa79b5 100644
--- a/src/ImageSharp/Common/Helpers/ImageMaths.cs
+++ b/src/ImageSharp/Common/Helpers/ImageMaths.cs
@@ -22,7 +22,7 @@ namespace SixLabors.ImageSharp
/// The blue component.
/// The .
[MethodImpl(InliningOptions.ShortMethod)]
- public static byte Get8BitBT709Luminance(byte r, byte g, byte b) => (byte)((r * .2126F) + (g * .7152F) + (b * .0722F));
+ public static byte Get8BitBT709Luminance(byte r, byte g, byte b) => (byte)((r * .2126F) + (g * .7152F) + (b * .0722F) + 0.5f);
///
/// Gets the luminance from the rgb components using the formula as specified by ITU-R Recommendation BT.709.
diff --git a/src/ImageSharp/PixelFormats/PixelImplementations/Gray8.cs b/src/ImageSharp/PixelFormats/PixelImplementations/Gray8.cs
index 4ed5904c2..512bee39d 100644
--- a/src/ImageSharp/PixelFormats/PixelImplementations/Gray8.cs
+++ b/src/ImageSharp/PixelFormats/PixelImplementations/Gray8.cs
@@ -18,6 +18,11 @@ namespace SixLabors.ImageSharp.PixelFormats
private static readonly Vector4 Half = new Vector4(0.5F);
private const float Average = 1 / 3F;
+ private static readonly Vector4 Min = new Vector4(0, 0, 0, 1f);
+ private static readonly Vector4 Max = Vector4.One;
+
+ private static readonly Vector4 Accumulator = new Vector4(255f * Average, 255f * Average, 255f * Average, 0.5f);
+
///
/// Initializes a new instance of the struct.
///
@@ -64,10 +69,12 @@ namespace SixLabors.ImageSharp.PixelFormats
[MethodImpl(InliningOptions.ShortMethod)]
public void FromVector4(Vector4 vector)
{
- vector *= MaxBytes;
- vector += Half;
- vector = Vector4.Clamp(vector, Vector4.Zero, MaxBytes) * Average;
- this.PackedValue = (byte)(vector.X + vector.Y + vector.Z);
+ vector = Vector4.Max(Min, vector);
+ vector = Vector4.Min(Max, vector);
+
+ float roundedSum = Vector4.Dot(vector, Accumulator);
+
+ this.PackedValue = (byte)roundedSum;
}
///
diff --git a/tests/ImageSharp.Tests/PixelFormats/Gray8Tests.cs b/tests/ImageSharp.Tests/PixelFormats/Gray8Tests.cs
index 6a7b20cbe..1e17985e6 100644
--- a/tests/ImageSharp.Tests/PixelFormats/Gray8Tests.cs
+++ b/tests/ImageSharp.Tests/PixelFormats/Gray8Tests.cs
@@ -1,14 +1,42 @@
// Copyright (c) Six Labors and contributors.
// Licensed under the Apache License, Version 2.0.
+using System.Diagnostics;
using System.Numerics;
+
+using SixLabors.ImageSharp.Common.Helpers;
using SixLabors.ImageSharp.PixelFormats;
using Xunit;
+// ReSharper disable InconsistentNaming
namespace SixLabors.ImageSharp.Tests.PixelFormats
{
public class Gray8Tests
{
+ public static readonly TheoryData LuminanceData = new TheoryData()
+ {
+ 0,
+ 1,
+ 2,
+ 3,
+ 5,
+ 13,
+ 31,
+ 71,
+ 73,
+ 79,
+ 83,
+ 109,
+ 127,
+ 128,
+ 131,
+ 199,
+ 250,
+ 251,
+ 254,
+ 255
+ };
+
[Theory]
[InlineData(0)]
[InlineData(255)]
@@ -34,9 +62,7 @@ namespace SixLabors.ImageSharp.Tests.PixelFormats
}
[Theory]
- [InlineData(0)]
- [InlineData(255)]
- [InlineData(30)]
+ [MemberData(nameof(LuminanceData))]
public void Gray8_ToScaledVector4(byte input)
{
// Arrange
@@ -53,26 +79,24 @@ namespace SixLabors.ImageSharp.Tests.PixelFormats
Assert.Equal(1, actual.W);
}
- [Fact]
- public void Gray8_FromVector4()
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void Gray8_FromVector4(byte luminance)
{
// Arrange
Gray8 gray = default;
- const int expected = 128;
- var vector = new Gray8(expected).ToVector4();
+ var vector = new Gray8(luminance).ToVector4();
// Act
gray.FromVector4(vector);
byte actual = gray.PackedValue;
// Assert
- Assert.Equal(expected, actual);
+ Assert.Equal(luminance, actual);
}
[Theory]
- [InlineData(0)]
- [InlineData(255)]
- [InlineData(30)]
+ [MemberData(nameof(LuminanceData))]
public void Gray8_ToVector4(byte input)
{
// Arrange
@@ -89,12 +113,12 @@ namespace SixLabors.ImageSharp.Tests.PixelFormats
Assert.Equal(1, actual.W);
}
- [Fact]
- public void Gray8_FromRgba32()
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void Gray8_FromRgba32(byte rgb)
{
// Arrange
Gray8 gray = default;
- const byte rgb = 128;
byte expected = ImageMaths.Get8BitBT709Luminance(rgb, rgb, rgb);
// Act
@@ -105,24 +129,124 @@ namespace SixLabors.ImageSharp.Tests.PixelFormats
Assert.Equal(expected, actual);
}
+
[Theory]
- [InlineData(0)]
- [InlineData(255)]
- [InlineData(30)]
- public void Gray8_ToRgba32(byte input)
+ [MemberData(nameof(LuminanceData))]
+ public void Gray8_ToRgba32(byte luminance)
{
// Arrange
- var gray = new Gray8(input);
+ var gray = new Gray8(luminance);
// Act
Rgba32 actual = default;
gray.ToRgba32(ref actual);
// Assert
- Assert.Equal(input, actual.R);
- Assert.Equal(input, actual.G);
- Assert.Equal(input, actual.B);
+ Assert.Equal(luminance, actual.R);
+ Assert.Equal(luminance, actual.G);
+ Assert.Equal(luminance, actual.B);
Assert.Equal(byte.MaxValue, actual.A);
}
+
+ public class Rgba32Compatibility
+ {
+ // ReSharper disable once MemberHidesStaticFromOuterClass
+ public static readonly TheoryData LuminanceData = Gray8Tests.LuminanceData;
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void Gray8_FromRgba32_IsInverseOf_ToRgba32(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ Gray8 mirror = default;
+ mirror.FromRgba32(rgba);
+
+ Assert.Equal(original, mirror);
+ }
+
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void Rgba32_ToGray8_IsInverseOf_Gray8_ToRgba32(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ Gray8 mirror = default;
+ mirror.FromRgba32(rgba);
+
+ Assert.Equal(original, mirror);
+ }
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void ToVector4_IsRgba32Compatible(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ var gray8Vector = original.ToVector4();
+ var rgbaVector = original.ToVector4();
+
+ Assert.Equal(gray8Vector, rgbaVector, new ApproximateFloatComparer(1e-5f));
+ }
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void FromVector4_IsRgba32Compatible(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ Vector4 rgbaVector = original.ToVector4();
+
+ Gray8 mirror = default;
+ mirror.FromVector4(rgbaVector);
+
+ Assert.Equal(original, mirror);
+ }
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void ToScaledVector4_IsRgba32Compatible(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ Vector4 gray8Vector = original.ToScaledVector4();
+ Vector4 rgbaVector = original.ToScaledVector4();
+
+ Assert.Equal(gray8Vector, rgbaVector, new ApproximateFloatComparer(1e-5f));
+ }
+
+ [Theory]
+ [MemberData(nameof(LuminanceData))]
+ public void FromScaledVector4_IsRgba32Compatible(byte luminance)
+ {
+ var original = new Gray8(luminance);
+
+ Rgba32 rgba = default;
+ original.ToRgba32(ref rgba);
+
+ Vector4 rgbaVector = original.ToScaledVector4();
+
+ Gray8 mirror = default;
+ mirror.FromScaledVector4(rgbaVector);
+
+ Assert.Equal(original, mirror);
+ }
+ }
}
}
\ No newline at end of file