procedure TMainForm.Button1Click(Sender: TObject);
var
  i,j:integer;
  c:TColor;
  x:TBitmap;
  r,g,b:integer;
  y,k:real;
begin
  x:=TBitmap.Create;
  x.Width:=x1.Width;
  x.Height:=x1.Height;
  x.Canvas.Draw(0,0,x1.Picture.Graphic); //JPEG
  for i:=0 to x1.Width-1 do
    for j:=0 to x1.Height-1 do
      begin
        c:=x.Canvas.Pixels[i,j];
        r:=getRValue(c);
        g:=getGValue(c);
        b:=getBValue(c);
        Y:=( 9798*R 19235*G 3735*B) / 32768;
        k:=1; //Y的比例
        x2.Picture.Bitmap.Canvas.Pixels[i,j]:=RGB(trunc(y*k),trunc(y*k),trunc(y*k));
      end;//for
   x.Free;
end;