Conversion between linear and sRGB

Author: ds5678

AssetRipper.TextureDecoder/Rgb/Color.cs

@@ -92,4 +92,30 @@ public static TTarget Convert<TThis, TThisChannelValue, TTarget, TTargetChannelV
 			return destination;
 		}
 	}
+
+	internal static TColor SRgbToLinear<TColor, TChannel>(this TColor color)
+		where TChannel : unmanaged
+		where TColor : unmanaged, IColor<TChannel>
+	{
+		color.GetChannels(out TChannel r, out TChannel g, out TChannel b, out TChannel a);
+		color.SetChannels(
+			SRgb.ToLinear(r),
+			SRgb.ToLinear(g),
+			SRgb.ToLinear(b),
+			a);
+		return color;
+	}
+
+	internal static TColor LinearToSRgb<TColor, TChannel>(this TColor color)
+		where TChannel : unmanaged
+		where TColor : unmanaged, IColor<TChannel>
+	{
+		color.GetChannels(out TChannel r, out TChannel g, out TChannel b, out TChannel a);
+		color.SetChannels(
+			SRgb.FromLinear(r),
+			SRgb.FromLinear(g),
+			SRgb.FromLinear(b),
+			a);
+		return color;
+	}
 }

AssetRipper.TextureDecoder/Rgb/RgbConverter.cs

@@ -64,5 +64,25 @@ static void ThrowDestinationSpanNotLargeEnough()
 				throw new ArgumentException("Destination span is not large enough to hold the converted data.", nameof(destinationSpan));
 			}
 		}
+
+		public static void SRgbToLinear<TColor, TChannel>(Span<TColor> span)
+			where TChannel : unmanaged
+			where TColor : unmanaged, IColor<TChannel>
+		{
+			for (int i = 0; i < span.Length; i++)
+			{
+				span[i] = span[i].SRgbToLinear<TColor, TChannel>();
+			}
+		}
+
+		public static void LinearToSRgb<TColor, TChannel>(Span<TColor> span)
+			where TChannel : unmanaged
+			where TColor : unmanaged, IColor<TChannel>
+		{
+			for (int i = 0; i < span.Length; i++)
+			{
+				span[i] = span[i].LinearToSRgb<TColor, TChannel>();
+			}
+		}
 	}
 }

AssetRipper.TextureDecoder/Rgb/SRgb.cs

@@ -0,0 +1,42 @@
+namespace AssetRipper.TextureDecoder.Rgb;
+
+internal static class SRgb
+{
+	public static T ToLinear<T>(T value) where T : unmanaged
+	{
+		double d = NumericConversion.Convert<T, double>(value);
+		d = SRgbToLinear(d);
+		return NumericConversion.Convert<double, T>(d);
+	}
+
+	public static T FromLinear<T>(T value) where T : unmanaged
+	{
+		double d = NumericConversion.Convert<T, double>(value);
+		d = LinearToSRgb(d);
+		return NumericConversion.Convert<double, T>(d);
+	}
+
+	private static double SRgbToLinear(double value)
+	{
+		if (value <= 0.04045)
+		{
+			return value / 12.92;
+		}
+		else
+		{
+			return double.Pow((value + 0.055) / 1.055, 2.4);
+		}
+	}
+
+	private static double LinearToSRgb(double value)
+	{
+		if (value <= 0.0031308)
+		{
+			return value * 12.92;
+		}
+		else
+		{
+			return 1.055 * double.Pow(value, 1.0 / 2.4) - 0.055;
+		}
+	}
+}