Optimize Color Parsing

This method was showing up in a profile of the startup of the .NET Podcasts app.

Optimize it to not allocate intermediate strings on .NET Core, and instead use Span operations.

src/Microsoft.Maui.Graphics/Color.NETCoreApp.cs

@@ -0,0 +1,72 @@
+using System;
+using System.Globalization;
+
+namespace Microsoft.Maui.Graphics
+{
+	public partial class Color
+	{
+		private static Color FromArgbImplementation(string colorAsHex)
+		{
+			ReadOnlySpan<char> colorAsHexSpan = colorAsHex;
+
+			//Skip # if present
+			if (colorAsHexSpan[0] == '#')
+				colorAsHexSpan = colorAsHexSpan.Slice(1);
+
+			int red = 0;
+			int green = 0;
+			int blue = 0;
+			int alpha = 255;
+
+			if (colorAsHexSpan.Length == 6)
+			{
+				//#RRGGBB
+				red = ParseInt(colorAsHexSpan.Slice(0, 2));
+				green = ParseInt(colorAsHexSpan.Slice(2, 2));
+				blue = ParseInt(colorAsHexSpan.Slice(4, 2));
+			}
+			else if (colorAsHexSpan.Length == 3)
+			{
+				//#RGB
+				Span<char> temp = stackalloc char[2];
+				temp[0] = temp[1] = colorAsHexSpan[0];
+				red = ParseInt(temp);
+
+				temp[0] = temp[1] = colorAsHexSpan[1];
+				green = ParseInt(temp);
+
+				temp[0] = temp[1] = colorAsHexSpan[2];
+				blue = ParseInt(temp);
+			}
+			else if (colorAsHexSpan.Length == 4)
+			{
+				//#ARGB
+				Span<char> temp = stackalloc char[2];
+				temp[0] = temp[1] = colorAsHexSpan[0];
+				alpha = ParseInt(temp);
+
+				temp[0] = temp[1] = colorAsHexSpan[1];
+				red = ParseInt(temp);
+
+				temp[0] = temp[1] = colorAsHexSpan[2];
+				green = ParseInt(temp);
+
+				temp[0] = temp[1] = colorAsHexSpan[3];
+				blue = ParseInt(temp);
+			}
+			else if (colorAsHexSpan.Length == 8)
+			{
+				//#AARRGGBB
+				alpha = ParseInt(colorAsHexSpan.Slice(0, 2));
+				red = ParseInt(colorAsHexSpan.Slice(2, 2));
+				green = ParseInt(colorAsHexSpan.Slice(4, 2));
+				blue = ParseInt(colorAsHexSpan.Slice(6, 2));
+			}
+
+			return FromRgba(red / 255f, green / 255f, blue / 255f, alpha / 255f);
+		}
+
+		private static int ParseInt(ReadOnlySpan<char> s) =>
+			int.Parse(s, NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
+	}
+}

src/Microsoft.Maui.Graphics/Color.Standard.cs

@@ -0,0 +1,56 @@
+using System.Globalization;
+
+namespace Microsoft.Maui.Graphics
+{
+	public partial class Color
+	{
+		private static Color FromArgbImplementation(string colorAsHex)
+		{
+			//Skip # if present
+			if (colorAsHex[0] == '#')
+				colorAsHex = colorAsHex.Substring(1);
+
+			int red = 0;
+			int green = 0;
+			int blue = 0;
+			int alpha = 255;
+
+			if (colorAsHex.Length == 6)
+			{
+				//#RRGGBB
+				red = ParseInt(colorAsHex.Substring(0, 2));
+				green = ParseInt(colorAsHex.Substring(2, 2));
+				blue = ParseInt(colorAsHex.Substring(4, 2));
+			}
+			else if (colorAsHex.Length == 3)
+			{
+				//#RGB
+				red = ParseInt($"{colorAsHex[0]}{colorAsHex[0]}");
+				green = ParseInt($"{colorAsHex[1]}{colorAsHex[1]}");
+				blue = ParseInt($"{colorAsHex[2]}{colorAsHex[2]}");
+			}
+			else if (colorAsHex.Length == 4)
+			{
+				//#ARGB
+				alpha = ParseInt($"{colorAsHex[0]}{colorAsHex[0]}");
+				red = ParseInt($"{colorAsHex[1]}{colorAsHex[1]}");
+				green = ParseInt($"{colorAsHex[2]}{colorAsHex[2]}");
+				blue = ParseInt($"{colorAsHex[3]}{colorAsHex[3]}");
+			}
+			else if (colorAsHex.Length == 8)
+			{
+				//#AARRGGBB
+				alpha = ParseInt(colorAsHex.Substring(0, 2));
+				red = ParseInt(colorAsHex.Substring(2, 2));
+				green = ParseInt(colorAsHex.Substring(4, 2));
+				blue = ParseInt(colorAsHex.Substring(6, 2));
+			}
+
+			return FromRgba(red / 255f, green / 255f, blue / 255f, alpha / 255f);
+		}
+
+		private static int ParseInt(string s) =>
+			int.Parse(s, NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
+
+	}
+}

src/Microsoft.Maui.Graphics/Color.cs

@@ -9,7 +9,7 @@ namespace Microsoft.Maui.Graphics
 {
 	[DebuggerDisplay("Red={Red}, Green={Green}, Blue={Blue}, Alpha={Alpha}")]
 	[TypeConverter(typeof(Converters.ColorTypeConverter))]
-	public class Color
+	public partial class Color
 	{
 		public readonly float Red;
 		public readonly float Green;
@@ -382,50 +382,7 @@ namespace Microsoft.Maui.Graphics
 			return FromRgba(red / 255f, green / 255f, blue / 255f, alpha / 255f);
 		}
 
-		public static Color FromArgb(string colorAsHex)
+		public static Color FromArgb(string colorAsHex) => FromArgbImplementation(colorAsHex);
-		{
-			//Remove # if present
-			if (colorAsHex.IndexOf('#') != -1)
-				colorAsHex = colorAsHex.Replace("#", "");
-
-			int red = 0;
-			int green = 0;
-			int blue = 0;
-			int alpha = 255;
-
-			if (colorAsHex.Length == 6)
-			{
-				//#RRGGBB
-				red = int.Parse(colorAsHex.Substring(0, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				green = int.Parse(colorAsHex.Substring(2, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				blue = int.Parse(colorAsHex.Substring(4, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-			}
-			else if (colorAsHex.Length == 3)
-			{
-				//#RGB
-				red = int.Parse($"{colorAsHex[0]}{colorAsHex[0]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				green = int.Parse($"{colorAsHex[1]}{colorAsHex[1]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				blue = int.Parse($"{colorAsHex[2]}{colorAsHex[2]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-			}
-			else if (colorAsHex.Length == 4)
-			{
-				//#ARGB
-				alpha = int.Parse($"{colorAsHex[0]}{colorAsHex[0]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				red = int.Parse($"{colorAsHex[1]}{colorAsHex[1]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				green = int.Parse($"{colorAsHex[2]}{colorAsHex[2]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				blue = int.Parse($"{colorAsHex[3]}{colorAsHex[3]}", NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-			}
-			else if (colorAsHex.Length == 8)
-			{
-				//#AARRGGBB
-				alpha = int.Parse(colorAsHex.Substring(0, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				red = int.Parse(colorAsHex.Substring(2, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				green = int.Parse(colorAsHex.Substring(4, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-				blue = int.Parse(colorAsHex.Substring(6, 2), NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture);
-			}
-
-			return FromRgba(red / 255f, green / 255f, blue / 255f, alpha / 255f);
-		}
 
 		public static Color FromHsla(float h, float s, float l, float a = 1)
 		{

src/Microsoft.Maui.Graphics/Microsoft.Maui.Graphics-net6.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>netstandard2.0;netstandard2.1;net6.0-ios;net6.0-android;net6.0-maccatalyst;net6.0-macos;net6.0-tizen6.5</TargetFrameworks>
+    <TargetFrameworks>netstandard2.0;netstandard2.1;net6.0;net6.0-ios;net6.0-android;net6.0-maccatalyst;net6.0-macos;net6.0-tizen6.5</TargetFrameworks>
     <TargetFrameworks Condition="$([MSBuild]::IsOSPlatform('windows')) and '$(MSBuildRuntimeType)' == 'Full'">$(TargetFrameworks);net6.0-windows10.0.18362</TargetFrameworks>
     <!-- Optional: Publish the repository URL in the built .nupkg (in the NuSpec <Repository> element) -->
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
@@ -23,9 +23,6 @@
     <PackageReference Include="System.Numerics.Vectors" Version="4.5.0" Condition="$(TargetFramework.StartsWith('netstandard'))" />
     <PackageReference Include="System.Drawing.Common" Version="6.0.0" Condition="$(TargetFramework.Contains('-windows'))" />
   </ItemGroup>
-  <ItemGroup>
-    <Folder Include="Windows\" />
-  </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Update="iOS\GraphicsiOS.resx">
       <Generator>ResXFileCodeGenerator</Generator>

src/targets/MultiTargeting.targets

@@ -52,10 +52,15 @@
     <None Include="**\*.Standard.cs"/>
     <Compile Remove="**\Standard\*.cs"/>
     <None Include="**\Standard\*.cs"/>
-    <Compile Remove="**\Standard\*.cs"/>
     <Reference Include="System.Numerics" />
     <Reference Include="System.Numerics.Vectors" />
   </ItemGroup>
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
+    <Compile Remove="**\*.NETCoreApp.cs"/>
+    <None Include="**\*.NETCoreApp.cs"/>
+    <Compile Remove="**\NETCoreApp\*.cs"/>
+    <None Include="**\NETCoreApp\*.cs"/>
+  </ItemGroup>
   <ItemGroup Condition="$(TargetFramework.StartsWith('netcoreapp')) != true ">
     <Compile Remove="**\*.Win32.cs"/>
     <None Include="**\*.Win32.cs"/>

tests/Microsoft.Maui.Graphics.Tests/Microsoft.Maui.Graphics.Tests-net6.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net5.0</TargetFramework>
+    <TargetFramework>net6.0</TargetFramework>
 
     <IsPackable>false</IsPackable>
   </PropertyGroup>