Is this code thread safe?

Is this code thread safe?

Can I access on Canvas of bitmap created on form1 but used only by my thread and not displayed / used by form1?

Eg:
TmyTh = class(TThread)
....
end;

TForm1 = class(TForm)
procedure Form create(...);
public
Bmp: TBitmap;
end;

procedure TForm1.FormCreate(...)
begin
Bmp := TBitmap.create;
....
end;

procedure TmyTh.execute;
begin
...
Form1. Bmp.Canvas.moveto(....);
Form1. Bmp.Canvas.lineto(....);
Form1. Bmp.SaveToFile(...);
end;