procedure TForm1.Button1Click(Sender: TObject);

var

 t: cardinal;

 x, y: integer;

 bm: TBitmap;

begin

 bm := TBitmap.Create;

 bm.PixelFormat := pf24bit;

 bm.Width := Form1.ClientWidth;

 bm.Height := Form1.ClientHeight;

 t := GetTickCount;

 for y := 0 to bm.Height - 1 do

  for x := 0 to bm.Width - 1 do

  bm.Canvas.Pixels[x,y] := RGB(x+y, x-y, y-x);

 Form1.Caption := IntToStr(GetTickCount - t);

 Form1.Canvas.Draw(0, 0, bm);

end;

procedure TForm1.Button2Click(Sender: TObject);

var

 t: cardinal;

 x, y: integer;

 bm: TBitmap;

 p: PByteArray;

begin

 bm := TBitmap.Create;

 bm.PixelFormat := pf24bit;

 bm.Width := Form1.ClientWidth;

 bm.Height := Form1.ClientHeight;

 t := GetTickCount;

 for y := 0 to bm.Height - 1 do

 begin

  p := bm.ScanLine[y];

  for x := 0 to bm.Width - 1 do

  begin

  p^[x*3] := x+y;

  p^[x*3+1] := x-y;

  p^[x*3+2] := y-x;

  end;

 end;

 Form1.Caption := IntToStr(GetTickCount - t);

 Form1.Canvas.Draw(0, 0, bm);

end;