added BitmapAlphaFormat that enables setting of alpha format that determines bitmap alpha pre-multiplication and enables alpha-blended painting of images

Components/ScintStylerInnoSetup.pas

@@ -130,6 +130,7 @@ type
     ssBackColor2,
     ssBackColorDirection,
     ssBackSolid,
+    ssBitmapAlphaFormat,
     ssChangesAssociations,
     ssChangesEnvironment,
     ssCloseApplications,

Projects/Compile.pas

@@ -89,6 +89,7 @@ type
     ssBackColor2,
     ssBackColorDirection,
     ssBackSolid,
+    ssBitmapAlphaFormat,
     ssChangesAssociations,
     ssChangesEnvironment,
     ssCloseApplications,
@@ -3684,6 +3685,16 @@ begin
     ssBackSolid: begin
         BackSolid := StrToBool(Value);
       end;
+    ssBitmapAlphaFormat: begin
+        if CompareText(Value, 'none') = 0 then
+          SetupHeader.BitmapAlphaFormat := afIgnored
+        else if CompareText(Value, 'defined') = 0 then
+          SetupHeader.BitmapAlphaFormat := afDefined
+        else if CompareText(Value, 'premultiplied') = 0 then
+          SetupHeader.BitmapAlphaFormat := afPremultiplied
+        else
+          Invalid;
+    end;
     ssChangesAssociations: begin
         SetSetupHeaderOption(shChangesAssociations);
       end;
@@ -8309,6 +8320,7 @@ begin
     SetupHeader.DefaultUserInfoOrg := '{sysuserinfoorg}';
     SetupHeader.BackColor := clBlue;
     SetupHeader.BackColor2 := clBlack;
+    SetupHeader.BitmapAlphaFormat := afIgnored;
     SetupHeader.DisableDirPage := dpAuto;
     SetupHeader.DisableProgramGroupPage := dpAuto;
     SetupHeader.CreateUninstallRegKey := 'yes';

Projects/Main.pas

@@ -250,7 +250,7 @@ uses
   Compress, CompressZlib, bzlib, LZMADecomp, ArcFour, SetupEnt, SelLangForm,
   Wizard, DebugClient, VerInfo, Extract, FileClass, Logging, MD5, SHA1,
   {$IFNDEF Delphi3orHigher} OLE2, {$ELSE} ActiveX, {$ENDIF}
-  SimpleExpression, Helper, SpawnClient, SpawnServer, LibFusion;
+  SimpleExpression, Helper, SpawnClient, SpawnServer, LibFusion, BitmapImage;
 
 {$R *.DFM}
 
@@ -2557,7 +2557,8 @@ var
     try
       ReadFileIntoStream(MemStream, R);
       MemStream.Seek(0, soFromBeginning);
-      WizardImage := TBitmap.Create;
+      WizardImage := TAlphaBitmap.Create;
+      TAlphaBitmap(WizardImage).AlphaFormat := TAlphaFormat(SetupHeader.BitmapAlphaFormat);
       WizardImage.LoadFromStream(MemStream);
     finally
       MemStream.Free;

Projects/Struct.pas

@@ -100,6 +100,7 @@ type
       NumRunEntries, NumUninstallRunEntries: Integer;
     MinVersion, OnlyBelowVersion: TSetupVersionData;
     BackColor, BackColor2, WizardImageBackColor: Longint;
+    BitmapAlphaFormat: (afIgnored, afDefined, afPremultiplied); // Same as Graphics.TAlphaFormat
     PasswordHash: TSHA1Digest;
     PasswordSalt: TSetupSalt;
     ExtraDiskSpaceRequired: Integer64;