procedure TForm2.Button1Click(Sender: TObject);
begin
  if OpenImageEnDialog1.Execute then
  begin
    Image1.io.Params.Width := Image1.Width;
    Image1.io.Params.Height := Image1.Height;
    Image1.IO.Params.JPEG_Scale := ioJPEG_AUTOCALC; // Access Violation
//    Image1.io.Params.JPEG_Scale := ioJPEG_FULLSIZE;  // Loads ok
    Image1.IO.LoadFromFile(OpenImageEnDialog1.FileName);
  end;

end;

procedure TForm2.FormShow(Sender: TObject);
begin
  Image1.IO.IEBitmap.Location:=ieFile;
  IEGlobalSettings.DefMinFileSize:=268435456;
end;

Access violation is in: jpegfilt:

function IEJPEG_Decomp_ReadScanlines(cinfo: IEJPEG_Decomp_Struct; scanlines: pointer; max_lines: cardinal): cardinal;
begin
  result := cinfo.readScanlines(scanlines, max_lines);
end;