欲清除 TImage 的圖形，可以使用:

Image1.Picture := nil;

或者：

procedure TForm1.Button1Click(Sender: TObject);
var
  ARect: TRect;
begin
  Image1.Canvas.CopyMode := cmWhiteness;    	
  ARect := Rect(0, 0, Image1.Picture.Width, Image1.Picture.Height);
  Image1.Canvas.CopyRect(ARect, Image1.Canvas, ARect);
  Image1.Canvas.Copymode := cmSrcCopy;
end;

    Source: geocities.com/huanlin_tsai/faq

               ( geocities.com/huanlin_tsai)