int TileBoundsCalculator::_calculateSplitY(const PixelBox& b)
{
  double total = _sumPixels(b);

  double bottom = _sumPixels(b.getRowBox(b.minY));

  int best = (b.maxY + b.minY) / 2;
  double bestSum = numeric_limits<double>::max();

  double thisSlop = _slop + 1.0 / (double)(b.maxY - b.minY);

  if (b.getHeight() < 6)
  {
    throw HootException("The input box must be at least six pixels high.");
  }

  for (int r = b.minY + 2; r < b.maxY - 2; r++)
  {
    double rowSum = _sumPixels(b.getRowBox(r));
    double rowSumMin = _sumPixels(b.getRowBox(r), _min) + _sumPixels(b.getRowBox(r + 1), _min);
    bottom += rowSum;

    double slop = abs(0.5 - bottom / total);
    if ((slop < thisSlop) && rowSumMin < bestSum)
    {
      best = r;
      bestSum = rowSumMin;
    }
  }

  if (bestSum == numeric_limits<double>::max())
  {
    LOG_WARN("bestSum isn't valid. " << b.toString() << " total: " << total << " size: " <<
             b.maxY - b.minY);
  }

  return best;
}