Set solid color wallpaper

Main.cs

@@ -275,6 +275,7 @@ public record class Configuration(
   ExpressSettingsMode ExpressSettings,
   ScriptSettings ScriptSettings,
   IKeySettings KeySettings,
+  IWallpaperSettings WallpaperSettings,
   bool BypassRequirementsCheck,
   bool BypassNetworkCheck,
   bool EnableLongPaths,
@@ -323,6 +324,7 @@ bool HideEdgeFre
     ExpressSettings: ExpressSettingsMode.DisableAll,
     ScriptSettings: new ScriptSettings([]),
     KeySettings: new SkipKeySettings(),
+    WallpaperSettings: new DefaultWallpaperSettings(),
     BypassRequirementsCheck: false,
     BypassNetworkCheck: false,
     EnableLongPaths: false,

UnattendGenerator.csproj

@@ -15,6 +15,7 @@
     <None Remove="resource\RemoveCapabilities.ps1" />
     <None Remove="resource\RemoveFeatures.ps1" />
     <None Remove="resource\RemovePackages.ps1" />
+    <None Remove="resource\SetWallpaper.ps1" />
     <None Remove="resource\ShowAllTrayIcons.ps1" />
   </ItemGroup>
 
@@ -30,6 +31,7 @@
     <EmbeddedResource Include="resource\Bloatware.json" />
     <EmbeddedResource Include="resource\known-writeable-folders.txt" />
     <EmbeddedResource Include="resource\DeleteTaskbarIcons.ps1" />
+    <EmbeddedResource Include="resource\SetWallpaper.ps1" />
     <EmbeddedResource Include="resource\ShowAllTrayIcons.ps1" />
     <EmbeddedResource Include="resource\RemoveBloatware.ps1" />
     <EmbeddedResource Include="resource\TimeOffset.json" />

modifier/Optimizations.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.IO;
 using System.Linq;
 
@@ -43,6 +44,14 @@ public record class ConfigureKeySettings(
   KeySetting ScrollLock
 ) : IKeySettings;
 
+public interface IWallpaperSettings;
+
+public class DefaultWallpaperSettings : IWallpaperSettings;
+
+public record class SolidWallpaperSettings(
+  Color Color
+) : IWallpaperSettings;
+
 class OptimizationsModifier(ModifierContext context) : Modifier(context)
 {
   public override void Process()
@@ -416,5 +425,24 @@ IEnumerable<string> SetExplorerOptions(string rootKey, string subKey)
         }
       }
     }
+    {
+      if (Configuration.WallpaperSettings is SolidWallpaperSettings settings)
+      {
+        string ps1File = @"C:\Windows\Setup\Scripts\SetWallpaper.ps1";
+        string script = Util.StringFromResource("SetWallpaper.ps1");
+        StringWriter writer = new();
+        writer.WriteLine($"$htmlColor = '{ColorTranslator.ToHtml(settings.Color)}';");
+        writer.WriteLine(script);
+        AddTextFile(writer.ToString(), ps1File);
+        appender.Append(
+          CommandBuilder.RegistryDefaultUserCommand((rootKey, subKey) =>
+          {
+            return [
+              CommandBuilder.UserRunOnceCommand(rootKey, subKey, "SetWallpaper", CommandBuilder.InvokePowerShellScript(ps1File)),
+            ];
+          })
+        );
+      }
+    }
   }
 }

resource/SetWallpaper.ps1

@@ -0,0 +1,32 @@
+Add-Type -TypeDefinition '
+	using System.Drawing;
+	using System.Runtime.InteropServices;
+	
+	public static class ColorSetter {
+		[DllImport("user32.dll")]
+		private static extern bool SetSysColors(
+			int cElements, 
+			int[] lpaElements,
+			int[] lpaRgbValues
+		);
+
+		[DllImport("user32.dll")]
+		private static extern bool SystemParametersInfo(
+			uint uiAction,
+			uint uiParam,
+			string pvParam,
+			uint fWinIni
+		);
+
+		public static void SetDesktopBackground(Color color) {
+			SystemParametersInfo(20, 0, "", 0);
+			SetSysColors(1, new int[] { 1 }, new int[] { ColorTranslator.ToWin32(color) });
+		}
+	}
+' -ReferencedAssemblies 'System.Drawing';
+
+$color = [System.Drawing.ColorTranslator]::FromHtml( $htmlColor );
+[ColorSetter]::SetDesktopBackground( $color );
+Set-ItemProperty -Path 'Registry::HKCU\Software\Microsoft\Windows\CurrentVersion\Explorer\Wallpapers' -Name 'BackgroundType' -Type 'DWord' -Value 1 -Force;
+Set-ItemProperty -Path 'Registry::HKCU\Control Panel\Desktop' -Name 'WallPaper' -Type 'String' -Value '' -Force;
+Set-ItemProperty -Path 'Registry::HKCU\Control Panel\Colors' -Name 'Background' -Type 'String' -Value "$($color.R) $($color.G) $($color.B)" -Force;