Negatif image

procedure TForm1.Negative1Click(Sender: TObject);
var
GrayPal: TMaxLogPalette;
i: Integer;
begin
for i := 0 to 255 do
with GrayPal.palPalEntry[i] do
begin
peRed := i;
peGreen := i;
peBlue := i;
peFlags := 0; end;
grayPal.palVersion := $0300;
GrayPal.palNumEntries := 256;
Image1.Picture.Bitmap.PixelFormat := pf8bit;
Image1.Picture.Bitmap.Palette := CreatePalette( PLogPalette(@GrayPal)^ );
Image1.Picture.Bitmap.Width := Image1.Picture.Bitmap.Width;
Image1.Picture.Bitmap.Height := Image1.Picture.Bitmap.Height;
Image1.Picture.Bitmap.Canvas.Draw( 0, 0, Image1.Picture.Bitmap);
end;