procedure TForm1.EncryptBMP(const BMP: TBitmap; Key: Integer);
var
  BytesPorScan: Integer;
  w, h: integer;
  p: pByteArray;
begin
  try
    BytesPorScan := Abs(Integer(BMP.ScanLine[1]) -
      Integer(BMP.ScanLine[0]));
  except
    raise Exception.Create('Error');
  end;
  RandSeed := Key;
  for h := 0 to BMP.Height - 1 do
  begin
    P := BMP.ScanLine[h];
    for w := 0 to BytesPorScan - 1 do
      P^[w] := P^[w] xor Random(256);
  end;
end;

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procedure TForm1.btn_encrypt_1Click(Sender: TObject);
begin
 EncryptBMP(ImageEnView1.Bitmap, 623);
 ImageEnView1.Refresh;
  ImageEnView1.IO.SaveToFile('C:\jpg_test\crypted_623.JPG');

end;