判斷圖片是否全白

function BMPisWhite(Bmp: TBitmap): Boolean;
type
  PRGBTripleArray = ^TRGBTripleArray;
  TRGBTripleArray = array[0..32767] of TRGBTriple;
var
  x, y:   integer;
  p0  :   PRGBTripleArray;
begin
  Result:=True;
  Bmp.PixelFormat := pf24bit;
  for y:=0 to Bmp.Height-1 do
  begin
    p0 := Bmp.ScanLine[y];
    for x:=0 to Bmp.Width-1 do
    begin
      if (p0[x].rgbtBlue <> 255) or (p0[x].rgbtGreen <> 255) or (p0[x].rgbtRed <> 255) then
      begin
        Result := False;
        Exit;
      end;
    end;
  end;
end;