Ako "read only" ?

toto Ti nefunguje ?

procedure TForm1.Button1Click(Sender: TObject);
begin
 With Image1.Picture.Bitmap.Canvas do
 begin
   Font.Color := clBlue;
   Brush.Style := bsclear;
   Font.Size := 13;
   TextOut(10, 10, 'Transparent Text!!');
 end;
end;

prípadne

procedure TForm1.Button1Click(Sender: TObject);
var
  OldBkMode : integer;
begin
 With Image1.Picture.Bitmap do
 begin
    Canvas.Font.Color := clBlue;
    OldBkMode := SetBkMode(Canvas.Handle,Ord(TRANSPARENT));
    Canvas.Font.Size := 13;
    Canvas.TextOut(10, 10, 'Transparent Text!!');
    SetBkMode(Canvas.Handle,OldBkMode);
 end;
end;