Function GatherPoints

deps/tesseract/classify/intfx.cpp:273–321

Gathers outline points and their directions from start_index into dirs by stepping along the outline and normalizing the coordinates until the required feature_length has been collected or end_index is reached. On input pos must point to the position corresponding to start_index and on return pos is updated to the current raw position, and pos_normed is set to the normed version of pos. Since dire

// dir and dir+128 (128 is 180 degrees) and then use the resulting mean
// with the least variance.
static int GatherPoints(const C_OUTLINE* outline, double feature_length,
                        const DENORM& denorm, const DENORM* root_denorm,
                        int start_index, int end_index,
                        ICOORD* pos, FCOORD* pos_normed,
                        LLSQ* points, LLSQ* dirs) {
  int step_length = outline->pathlength();
  ICOORD step = outline->step(start_index % step_length);
  // Prev_normed is the start point of this collection and will be set on the
  // first iteration, and on later iterations used to determine the length
  // that has been collected.
  FCOORD prev_normed;
  points->clear();
  dirs->clear();
  int num_points = 0;
  int index;
  for (index = start_index; index <= end_index; ++index, *pos += step) {
    step = outline->step(index % step_length);
    int edge_weight = outline->edge_strength_at_index(index % step_length);
    if (edge_weight == 0) {
      // This point has conflicting gradient and step direction, so ignore it.
      continue;
    }
    // Get the sub-pixel precise location and normalize.
    FCOORD f_pos = outline->sub_pixel_pos_at_index(*pos, index % step_length);
    denorm.NormTransform(root_denorm, f_pos, pos_normed);
    if (num_points == 0) {
      // The start of this segment.
      prev_normed = *pos_normed;
    } else {
      FCOORD offset = *pos_normed - prev_normed;
      float length = offset.length();
      if (length > feature_length) {
        // We have gone far enough from the start. We will use this point in
        // the next set so return what we have so far.
        return index;
      }
    }
    points->add(pos_normed->x(), pos_normed->y(), edge_weight);
    int direction = outline->direction_at_index(index % step_length);
    if (direction >= 0) {
      direction = NormalizeDirection(direction, f_pos, denorm, root_denorm);
      // Use both the direction and direction +128 so we are not trying to
      // take the mean of something straddling the wrap-around point.
      dirs->add(direction, Modulo(direction + 128, 256));
    }
    ++num_points;
  }
  return index;
}

// Extracts Tesseract features and appends them to the features vector.
// Startpt to lastpt, inclusive, MUST have the same src_outline member,