C++ BLOBNBOX::bounding_box方法代码示例

// Finds vertical lines in the given list of BLOBNBOXes. bleft and tright
// are the bounds of the image on which the input line_bblobs were found.
// The input line_bblobs list is const really.
// The output vertical_x and vertical_y are the total of all the vectors.
// The output list of TabVector makes no reference to the input BLOBNBOXes.
void LineFinder::FindLineVectors(const ICOORD& bleft, const ICOORD& tright,
                                 BLOBNBOX_LIST* line_bblobs,
                                 int* vertical_x, int* vertical_y,
                                 TabVector_LIST* vectors) {
  BLOBNBOX_IT bbox_it(line_bblobs);
  int b_count = 0;
  // Put all the blobs into the grid to find the lines, and move the blobs
  // to the output lists.
  AlignedBlob blob_grid(kLineFindGridSize, bleft, tright);
  for (bbox_it.mark_cycle_pt(); !bbox_it.cycled_list(); bbox_it.forward()) {
    BLOBNBOX* bblob = bbox_it.data();
    bblob->set_left_tab_type(TT_UNCONFIRMED);
    bblob->set_left_rule(bleft.x());
    bblob->set_right_rule(tright.x());
    bblob->set_left_crossing_rule(bleft.x());
    bblob->set_right_crossing_rule(tright.x());
    blob_grid.InsertBBox(false, true, bblob);
    ++b_count;
  }
  if (textord_debug_tabfind)
    tprintf("Inserted %d line blobs into grid\n", b_count);
  if (b_count == 0)
    return;

  // Search the entire grid, looking for vertical line vectors.
  GridSearch<BLOBNBOX, BLOBNBOX_CLIST, BLOBNBOX_C_IT> lsearch(&blob_grid);
  BLOBNBOX* bbox;
  TabVector_IT vector_it(vectors);
  *vertical_x = 0;
  *vertical_y = 1;
  lsearch.StartFullSearch();
  while ((bbox = lsearch.NextFullSearch()) != NULL) {
    if (bbox->left_tab_type() == TT_UNCONFIRMED) {
      const TBOX& box = bbox->bounding_box();
      if (AlignedBlob::WithinTestRegion(2, box.left(), box.bottom()))
        tprintf("Finding line vector starting at bbox (%d,%d)\n",
                box.left(), box.bottom());
      AlignedBlobParams align_params(*vertical_x, *vertical_y, box.width());
      TabVector* vector = blob_grid.FindVerticalAlignment(align_params, bbox,
                                                          vertical_x,
                                                          vertical_y);
      if (vector != NULL) {
        vector->Freeze();
        vector_it.add_to_end(vector);
      }
    }
  }
  ScrollView* line_win = NULL;
  if (textord_tabfind_show_vlines) {
    line_win = blob_grid.MakeWindow(0, 50, "Vlines");
    blob_grid.DisplayBoxes(line_win);
    line_win = blob_grid.DisplayTabs("Vlines", line_win);
  }
}

// Tests each blob in the list to see if it is certain non-text using 2
// conditions:
// 1. blob overlaps a cell with high value in noise_density_ (previously set
// by ComputeNoiseDensity).
// OR 2. The blob overlaps more than max_blob_overlaps in *this grid. This
// condition is disabled with max_blob_overlaps == -1.
// If it does, the blob is declared non-text, and is used to mark up the
// nontext_mask. Such blobs are fully deleted, and non-noise blobs have their
// neighbours reset, as they may now point to deleted data.
// WARNING: The blobs list blobs may be in the *this grid, but they are
// not removed. If any deleted blobs might be in *this, then this must be
// Clear()ed immediately after MarkAndDeleteNonTextBlobs is called.
// If the win is not NULL, deleted blobs are drawn on it in red, and kept
// blobs are drawn on it in ok_color.
void CCNonTextDetect::MarkAndDeleteNonTextBlobs(BLOBNBOX_LIST* blobs,
        int max_blob_overlaps,
        ScrollView* win,
        ScrollView::Color ok_color,
        Pix* nontext_mask) {
    int imageheight = tright().y() - bleft().x();
    BLOBNBOX_IT blob_it(blobs);
    BLOBNBOX_LIST dead_blobs;
    BLOBNBOX_IT dead_it(&dead_blobs);
    for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
        BLOBNBOX* blob = blob_it.data();
        TBOX box = blob->bounding_box();
        if (!noise_density_->RectMostlyOverThreshold(box, max_noise_count_) &&
                (max_blob_overlaps < 0 ||
                 !BlobOverlapsTooMuch(blob, max_blob_overlaps))) {
            blob->ClearNeighbours();
#ifndef GRAPHICS_DISABLED
            if (win != NULL)
                blob->plot(win, ok_color, ok_color);
#endif  // GRAPHICS_DISABLED
        } else {
            if (noise_density_->AnyZeroInRect(box)) {
                // There is a danger that the bounding box may overlap real text, so
                // we need to render the outline.
                Pix* blob_pix = blob->cblob()->render_outline();
                pixRasterop(nontext_mask, box.left(), imageheight - box.top(),
                            box.width(), box.height(), PIX_SRC | PIX_DST,
                            blob_pix, 0, 0);
                pixDestroy(&blob_pix);
            } else {
                if (box.area() < gridsize() * gridsize()) {
                    // It is a really bad idea to make lots of small components in the
                    // photo mask, so try to join it to a bigger area by expanding the
                    // box in a way that does not touch any zero noise density cell.
                    box = AttemptBoxExpansion(box, *noise_density_, gridsize());
                }
                // All overlapped cells are non-zero, so just mark the rectangle.
                pixRasterop(nontext_mask, box.left(), imageheight - box.top(),
                            box.width(), box.height(), PIX_SET, NULL, 0, 0);
            }
#ifndef GRAPHICS_DISABLED
            if (win != NULL)
                blob->plot(win, ScrollView::RED, ScrollView::RED);
#endif  // GRAPHICS_DISABLED
            // It is safe to delete the cblob now, as it isn't used by the grid
            // or BlobOverlapsTooMuch, and the BLOBNBOXes will go away with the
            // dead_blobs list.
            // TODO(rays) delete the delete when the BLOBNBOX destructor deletes
            // the cblob.
            delete blob->cblob();
            dead_it.add_to_end(blob_it.extract());
        }
    }
}

// Extend this vector to include the supplied blob if it doesn't
// already have it.
void TabVector::ExtendToBox(BLOBNBOX* new_blob) {
  TBOX new_box = new_blob->bounding_box();
  BLOBNBOX_C_IT it(&boxes_);
  if (!it.empty()) {
    BLOBNBOX* blob = it.data();
    TBOX box = blob->bounding_box();
    while (!it.at_last() && box.top() <= new_box.top()) {
      if (blob == new_blob)
        return;  // We have it already.
      it.forward();
      blob = it.data();
      box = blob->bounding_box();
    }
    if (box.top() >= new_box.top()) {
      it.add_before_stay_put(new_blob);
      needs_refit_ = true;
      return;
    }
  }
  needs_refit_ = true;
  it.add_after_stay_put(new_blob);
}

// Returns the box gaps between this and its neighbours_ in an array
// indexed by BlobNeighbourDir.
void BLOBNBOX::NeighbourGaps(int gaps[BND_COUNT]) const {
  for (int dir = 0; dir < BND_COUNT; ++dir) {
    gaps[dir] = MAX_INT16;
    BLOBNBOX* neighbour = neighbours_[dir];
    if (neighbour != NULL) {
      TBOX n_box = neighbour->bounding_box();
      if (dir == BND_LEFT || dir == BND_RIGHT) {
        gaps[dir] = box.x_gap(n_box);
      } else {
        gaps[dir] = box.y_gap(n_box);
      }
    }
  }
}

// Moves blobs that look like they don't sit well on a textline from the
// input blobs list to the output small_blobs list.
// This gets them away from initial textline finding to stop diacritics
// from forming incorrect textlines. (Introduced mainly to fix Thai.)
void TextlineProjection::MoveNonTextlineBlobs(
    BLOBNBOX_LIST* blobs, BLOBNBOX_LIST* small_blobs) const {
  BLOBNBOX_IT it(blobs);
  BLOBNBOX_IT small_it(small_blobs);
  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
    BLOBNBOX* blob = it.data();
    const TBOX& box = blob->bounding_box();
    bool debug = AlignedBlob::WithinTestRegion(2, box.left(),
                                               box.bottom());
    if (BoxOutOfHTextline(box, NULL, debug) && !blob->UniquelyVertical()) {
      blob->ClearNeighbours();
      small_it.add_to_end(it.extract());
    }
  }
}

TBOX box_next_pre_chopped(                 //get bounding box
                         BLOBNBOX_IT *it  //iterator to blobds
                        ) {
  BLOBNBOX *blob;                //current blob
  TBOX result;                    //total box

  blob = it->data ();
  result = blob->bounding_box ();
  do {
    it->forward ();
    blob = it->data ();
  }
                                 //until next real blob
  while (blob->joined_to_prev ());
  return result;
}

// Finds vertical line objects in the given pix.
// Uses the given resolution to determine size thresholds instead of any
// that may be present in the pix.
// The output vertical_x and vertical_y contain a sum of the output vectors,
// thereby giving the mean vertical direction.
// The output vectors are owned by the list and Frozen (cannot refit) by
// having no boxes, as there is no need to refit or merge separator lines.
void LineFinder::FindVerticalLines(int resolution,  Pix* pix,
                                   int* vertical_x, int* vertical_y,
                                   TabVector_LIST* vectors) {
#ifdef HAVE_LIBLEPT
  Pix* line_pix;
  Boxa* boxes = GetVLineBoxes(resolution, pix, &line_pix);
  C_BLOB_LIST line_cblobs;
  int width = pixGetWidth(pix);
  int height = pixGetHeight(pix);
  ConvertBoxaToBlobs(width, height, &boxes, &line_cblobs);
  // Make the BLOBNBOXes from the C_BLOBs.
  BLOBNBOX_LIST line_bblobs;
  C_BLOB_IT blob_it(&line_cblobs);
  BLOBNBOX_IT bbox_it(&line_bblobs);
  for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
    C_BLOB* cblob = blob_it.data();
    BLOBNBOX* bblob = new BLOBNBOX(cblob);
    bbox_it.add_to_end(bblob);
  }
  ICOORD bleft(0, 0);
  ICOORD tright(width, height);
  FindLineVectors(bleft, tright, &line_bblobs, vertical_x, vertical_y, vectors);
  if (!vectors->empty()) {
    // Some lines were found, so erase the unused blobs from the line image
    // and then subtract the line image from the source.
    bbox_it.move_to_first();
    for (bbox_it.mark_cycle_pt(); !bbox_it.cycled_list(); bbox_it.forward()) {
      BLOBNBOX* blob = bbox_it.data();
      if (blob->left_tab_type() == TT_UNCONFIRMED) {
        const TBOX& box = blob->bounding_box();
        Box* pixbox = boxCreate(box.left(), height - box.top(),
                                box.width(), box.height());
        pixClearInRect(line_pix, pixbox);
        boxDestroy(&pixbox);
      }
    }
    pixDilateBrick(line_pix, line_pix, 1, 3);
    pixSubtract(pix, pix, line_pix);
    if (textord_tabfind_show_vlines)
      pixWrite("vlinesclean.png", line_pix, IFF_PNG);
    ICOORD vertical;
    vertical.set_with_shrink(*vertical_x, *vertical_y);
    TabVector::MergeSimilarTabVectors(vertical, vectors, NULL);
  }
  pixDestroy(&line_pix);
#endif
}

// Display the blobs in the window colored according to textline quality.
void TextlineProjection::PlotGradedBlobs(BLOBNBOX_LIST* blobs,
                                         ScrollView* win) {
#ifndef GRAPHICS_DISABLED
  BLOBNBOX_IT it(blobs);
  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
    BLOBNBOX* blob = it.data();
    const TBOX& box = blob->bounding_box();
    bool bad_box = BoxOutOfHTextline(box, NULL, false);
    if (blob->UniquelyVertical())
      win->Pen(ScrollView::YELLOW);
    else
      win->Pen(bad_box ? ScrollView::RED : ScrollView::BLUE);
    win->Rectangle(box.left(), box.bottom(), box.right(), box.top());
  }
  win->Update();
#endif  // GRAPHICS_DISABLED
}

// Display the tab codes of the BLOBNBOXes in this grid.
ScrollView* AlignedBlob::DisplayTabs(const char* window_name,
                                     ScrollView* tab_win) {
#ifndef GRAPHICS_DISABLED
  if (tab_win == nullptr)
    tab_win = MakeWindow(0, 50, window_name);
  // For every tab in the grid, display it.
  GridSearch<BLOBNBOX, BLOBNBOX_CLIST, BLOBNBOX_C_IT> gsearch(this);
  gsearch.StartFullSearch();
  BLOBNBOX* bbox;
  while ((bbox = gsearch.NextFullSearch()) != nullptr) {
    const TBOX& box = bbox->bounding_box();
    int left_x = box.left();
    int right_x = box.right();
    int top_y = box.top();
    int bottom_y = box.bottom();
    TabType tabtype = bbox->left_tab_type();
    if (tabtype != TT_NONE) {
      if (tabtype == TT_MAYBE_ALIGNED)
        tab_win->Pen(ScrollView::BLUE);
      else if (tabtype == TT_MAYBE_RAGGED)
        tab_win->Pen(ScrollView::YELLOW);
      else if (tabtype == TT_CONFIRMED)
        tab_win->Pen(ScrollView::GREEN);
      else
        tab_win->Pen(ScrollView::GREY);
      tab_win->Line(left_x, top_y, left_x, bottom_y);
    }
    tabtype = bbox->right_tab_type();
    if (tabtype != TT_NONE) {
      if (tabtype == TT_MAYBE_ALIGNED)
        tab_win->Pen(ScrollView::MAGENTA);
      else if (tabtype == TT_MAYBE_RAGGED)
        tab_win->Pen(ScrollView::ORANGE);
      else if (tabtype == TT_CONFIRMED)
        tab_win->Pen(ScrollView::RED);
      else
        tab_win->Pen(ScrollView::GREY);
      tab_win->Line(right_x, top_y, right_x, bottom_y);
    }
  }
  tab_win->Update();
#endif
  return tab_win;
}

// Returns true if the given blob overlaps more than max_overlaps blobs
// in the current grid.
bool CCNonTextDetect::BlobOverlapsTooMuch(BLOBNBOX* blob, int max_overlaps) {
    // Search the grid to see what intersects it.
    // Setup a Rectangle search for overlapping this blob.
    BlobGridSearch rsearch(this);
    TBOX box = blob->bounding_box();
    rsearch.StartRectSearch(box);
    rsearch.SetUniqueMode(true);
    BLOBNBOX* neighbour;
    int overlap_count = 0;
    while (overlap_count <= max_overlaps &&
            (neighbour = rsearch.NextRectSearch()) != NULL) {
        if (box.major_overlap(neighbour->bounding_box())) {
            ++overlap_count;
            if (overlap_count > max_overlaps)
                return true;
        }
    }
    return false;
}

// Sets up displacement_modes_ with the top few modes of the perpendicular
// distance of each blob from the given direction vector, after rounding.
void BaselineRow::SetupBlobDisplacements(const FCOORD& direction) {
  // Set of perpendicular displacements of the blob bottoms from the required
  // baseline direction.
  GenericVector<double> perp_blob_dists;
  displacement_modes_.truncate(0);
  // Gather the skew-corrected position of every blob.
  double min_dist = MAX_FLOAT32;
  double max_dist = -MAX_FLOAT32;
  BLOBNBOX_IT blob_it(blobs_);
  bool debug = false;
  for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
    BLOBNBOX* blob = blob_it.data();
    const TBOX& box = blob->bounding_box();
#ifdef kDebugYCoord
    if (box.bottom() < kDebugYCoord && box.top() > kDebugYCoord) debug = true;
#endif
    FCOORD blob_pos((box.left() + box.right()) / 2.0f,
                    blob->baseline_position());
    double offset = direction * blob_pos;
    perp_blob_dists.push_back(offset);
    if (debug) {
      tprintf("Displacement %g for blob at:", offset);
      box.print();
    }
    UpdateRange(offset, &min_dist, &max_dist);
  }
  // Set up a histogram using disp_quant_factor_ as the bucket size.
  STATS dist_stats(IntCastRounded(min_dist / disp_quant_factor_),
                   IntCastRounded(max_dist / disp_quant_factor_) + 1);
  for (int i = 0; i < perp_blob_dists.size(); ++i) {
    dist_stats.add(IntCastRounded(perp_blob_dists[i] / disp_quant_factor_), 1);
  }
  GenericVector<KDPairInc<float, int> > scaled_modes;
  dist_stats.top_n_modes(kMaxDisplacementsModes, &scaled_modes);
  if (debug) {
    for (int i = 0; i < scaled_modes.size(); ++i) {
      tprintf("Top mode = %g * %d\n",
              scaled_modes[i].key * disp_quant_factor_, scaled_modes[i].data);
    }
  }
  for (int i = 0; i < scaled_modes.size(); ++i)
    displacement_modes_.push_back(disp_quant_factor_ * scaled_modes[i].key);
}

// Places a copy of blobs that are near a word (after applying rotation to the
// blob) in the most appropriate word, unless there is doubt, in which case a
// blob can end up in two words. Source blobs are not touched.
void Textord::TransferDiacriticsToWords(BLOBNBOX_LIST* diacritic_blobs,
                                        const FCOORD& rotation,
                                        WordGrid* word_grid) {
  WordSearch ws(word_grid);
  BLOBNBOX_IT b_it(diacritic_blobs);
  // Apply rotation to each blob before finding the nearest words. The rotation
  // allows us to only consider above/below placement and not left/right on
  // vertical text, because all text is horizontal here.
  for (b_it.mark_cycle_pt(); !b_it.cycled_list(); b_it.forward()) {
    BLOBNBOX* blobnbox = b_it.data();
    TBOX blob_box = blobnbox->bounding_box();
    blob_box.rotate(rotation);
    ws.StartRectSearch(blob_box);
    // Above/below refer to word position relative to diacritic. Since some
    // scripts eg Kannada/Telugu habitually put diacritics below words, and
    // others eg Thai/Vietnamese/Latin put most diacritics above words, try
    // for both if there isn't much in it.
    WordWithBox* best_above_word = nullptr;
    WordWithBox* best_below_word = nullptr;
    int best_above_distance = 0;
    int best_below_distance = 0;
    for (WordWithBox* word = ws.NextRectSearch(); word != nullptr;
         word = ws.NextRectSearch()) {
      if (word->word()->flag(W_REP_CHAR)) continue;
      TBOX word_box = word->true_bounding_box();
      int x_distance = blob_box.x_gap(word_box);
      int y_distance = blob_box.y_gap(word_box);
      if (x_distance > 0) {
        // Arbitrarily divide x-distance by 2 if there is a major y overlap,
        // and the word is to the left of the diacritic. If the
        // diacritic is a dropped broken character between two words, this will
        // help send all the pieces to a single word, instead of splitting them
        // over the 2 words.
        if (word_box.major_y_overlap(blob_box) &&
            blob_box.left() > word_box.right()) {
          x_distance /= 2;
        }
        y_distance += x_distance;
      }
      if (word_box.y_middle() > blob_box.y_middle() &&
          (best_above_word == nullptr || y_distance < best_above_distance)) {
        best_above_word = word;
        best_above_distance = y_distance;
      }
      if (word_box.y_middle() <= blob_box.y_middle() &&
          (best_below_word == nullptr || y_distance < best_below_distance)) {
        best_below_word = word;
        best_below_distance = y_distance;
      }
    }
    bool above_good =
        best_above_word != nullptr &&
        (best_below_word == nullptr ||
         best_above_distance < best_below_distance + blob_box.height());
    bool below_good =
        best_below_word != nullptr && best_below_word != best_above_word &&
        (best_above_word == nullptr ||
         best_below_distance < best_above_distance + blob_box.height());
    if (below_good) {
      C_BLOB* copied_blob = C_BLOB::deep_copy(blobnbox->cblob());
      copied_blob->rotate(rotation);
      // Put the blob into the word's reject blobs list.
      C_BLOB_IT blob_it(best_below_word->RejBlobs());
      blob_it.add_to_end(copied_blob);
    }
    if (above_good) {
      C_BLOB* copied_blob = C_BLOB::deep_copy(blobnbox->cblob());
      copied_blob->rotate(rotation);
      // Put the blob into the word's reject blobs list.
      C_BLOB_IT blob_it(best_above_word->RejBlobs());
      blob_it.add_to_end(copied_blob);
    }
  }
}

// (Re)Fit a line to the stored points. Returns false if the line
// is degenerate. Althougth the TabVector code mostly doesn't care about the
// direction of lines, XAtY would give silly results for a horizontal line.
// The class is mostly aimed at use for vertical lines representing
// horizontal tab stops.
bool TabVector::Fit(ICOORD vertical, bool force_parallel) {
  needs_refit_ = false;
  if (boxes_.empty()) {
    // Don't refit something with no boxes, as that only happens
    // in Evaluate, and we don't want to end up with a zero vector.
    if (!force_parallel)
      return false;
    // If we are forcing parallel, then we just need to set the sort_key_.
    ICOORD midpt = startpt_;
    midpt += endpt_;
    midpt /= 2;
    sort_key_ = SortKey(vertical, midpt.x(), midpt.y());
    return startpt_.y() != endpt_.y();
  }
  if (!force_parallel && !IsRagged()) {
    // Use a fitted line as the vertical.
    DetLineFit linepoints;
    BLOBNBOX_C_IT it(&boxes_);
    // Fit a line to all the boxes in the list.
    for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
      BLOBNBOX* bbox = it.data();
      TBOX box = bbox->bounding_box();
      int x1 = IsRightTab() ? box.right() : box.left();
      ICOORD boxpt(x1, box.bottom());
      linepoints.Add(boxpt);
      if (it.at_last()) {
        ICOORD top_pt(x1, box.top());
        linepoints.Add(top_pt);
      }
    }
    linepoints.Fit(&startpt_, &endpt_);
    if (startpt_.y() != endpt_.y()) {
      vertical = endpt_;
      vertical -= startpt_;
    }
  }
  int start_y = startpt_.y();
  int end_y = endpt_.y();
  sort_key_ = IsLeftTab() ? MAX_INT32 : -MAX_INT32;
  BLOBNBOX_C_IT it(&boxes_);
  // Choose a line parallel to the vertical such that all boxes are on the
  // correct side of it.
  mean_width_ = 0;
  int width_count = 0;
  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
    BLOBNBOX* bbox = it.data();
    TBOX box = bbox->bounding_box();
    mean_width_ += box.width();
    ++width_count;
    int x1 = IsRightTab() ? box.right() : box.left();
    // Test both the bottom and the top, as one will be more extreme, depending
    // on the direction of skew.
    int bottom_y = box.bottom();
    int top_y = box.top();
    int key = SortKey(vertical, x1, bottom_y);
    if (IsLeftTab() == (key < sort_key_)) {
      sort_key_ = key;
      startpt_ = ICOORD(x1, bottom_y);
    }
    key = SortKey(vertical, x1, top_y);
    if (IsLeftTab() == (key < sort_key_)) {
      sort_key_ = key;
      startpt_ = ICOORD(x1, top_y);
    }
    if (it.at_first())
      start_y = bottom_y;
    if (it.at_last())
      end_y = top_y;
  }
  if (width_count > 0) {
    mean_width_ = (mean_width_ + width_count - 1) / width_count;
  }
  endpt_ = startpt_ + vertical;
  needs_evaluation_ = true;
  if (start_y != end_y) {
    // Set the ends of the vector to fully include the first and last blobs.
    startpt_.set_x(XAtY(vertical, sort_key_, start_y));
    startpt_.set_y(start_y);
    endpt_.set_x(XAtY(vertical, sort_key_, end_y));
    endpt_.set_y(end_y);
    return true;
  }
  return false;
}

// Fits a straight baseline to the points. Returns true if it had enough
// points to be reasonably sure of the fitted baseline.
// If use_box_bottoms is false, baselines positions are formed by
// considering the outlines of the blobs.
bool BaselineRow::FitBaseline(bool use_box_bottoms) {
  // Deterministic fitting is used wherever possible.
  fitter_.Clear();
  // Linear least squares is a backup if the DetLineFit produces a bad line.
  LLSQ llsq;
  BLOBNBOX_IT blob_it(blobs_);

  for (blob_it.mark_cycle_pt(); !blob_it.cycled_list(); blob_it.forward()) {
    BLOBNBOX* blob = blob_it.data();
    if (!use_box_bottoms) blob->EstimateBaselinePosition();
    const TBOX& box = blob->bounding_box();
    int x_middle = (box.left() + box.right()) / 2;
#ifdef kDebugYCoord
    if (box.bottom() < kDebugYCoord && box.top() > kDebugYCoord) {
      tprintf("Box bottom = %d, baseline pos=%d for box at:",
              box.bottom(), blob->baseline_position());
      box.print();
    }
#endif
    fitter_.Add(ICOORD(x_middle, blob->baseline_position()), box.width() / 2);
    llsq.add(x_middle, blob->baseline_position());
  }
  // Fit the line.
  ICOORD pt1, pt2;
  baseline_error_ = fitter_.Fit(&pt1, &pt2);
  baseline_pt1_ = pt1;
  baseline_pt2_ = pt2;
  if (baseline_error_ > max_baseline_error_ &&
      fitter_.SufficientPointsForIndependentFit()) {
    // The fit was bad but there were plenty of points, so try skipping
    // the first and last few, and use the new line if it dramatically improves
    // the error of fit.
    double error = fitter_.Fit(kNumSkipPoints, kNumSkipPoints, &pt1, &pt2);
    if (error < baseline_error_ / 2.0) {
      baseline_error_ = error;
      baseline_pt1_ = pt1;
      baseline_pt2_ = pt2;
    }
  }
  int debug = 0;
#ifdef kDebugYCoord
  Print();
  debug = bounding_box_.bottom() < kDebugYCoord &&
      bounding_box_.top() > kDebugYCoord
            ? 3 : 2;
#endif
  // Now we obtained a direction from that fit, see if we can improve the
  // fit using the same direction and some other start point.
  FCOORD direction(pt2 - pt1);
  double target_offset = direction * pt1;
  good_baseline_ = false;
  FitConstrainedIfBetter(debug, direction, 0.0, target_offset);
  // Wild lines can be produced because DetLineFit allows vertical lines, but
  // vertical text has been rotated so angles over pi/4 should be disallowed.
  // Near vertical lines can still be produced by vertically aligned components
  // on very short lines.
  double angle = BaselineAngle();
  if (fabs(angle) > M_PI * 0.25) {
    // Use the llsq fit as a backup.
    baseline_pt1_ = llsq.mean_point();
    baseline_pt2_ = baseline_pt1_ + FCOORD(1.0f, llsq.m());
    // TODO(rays) get rid of this when m and c are no longer used.
    double m = llsq.m();
    double c = llsq.c(m);
    baseline_error_ = llsq.rms(m, c);
    good_baseline_ = false;
  }
  return good_baseline_;
}

// Return true if this vector is the same side, overlaps, and close
// enough to the other to be merged.
bool TabVector::SimilarTo(const ICOORD& vertical,
                          const TabVector& other, BlobGrid* grid) const {
  if ((IsRightTab() && other.IsRightTab()) ||
      (IsLeftTab() && other.IsLeftTab())) {
    // If they don't overlap, at least in extensions, then there is no chance.
    if (ExtendedOverlap(other.extended_ymax_, other.extended_ymin_) < 0)
      return false;
    // A fast approximation to the scale factor of the sort_key_.
    int v_scale = abs(vertical.y());
    if (v_scale == 0)
      v_scale = 1;
    // If they are close enough, then OK.
    if (sort_key_ + kSimilarVectorDist * v_scale >= other.sort_key_ &&
        sort_key_ - kSimilarVectorDist * v_scale <= other.sort_key_)
      return true;
    // Ragged tabs get a bigger threshold.
    if (!IsRagged() || !other.IsRagged() ||
        sort_key_ + kSimilarRaggedDist * v_scale < other.sort_key_ ||
        sort_key_ - kSimilarRaggedDist * v_scale > other.sort_key_)
      return false;
    if (grid == NULL) {
      // There is nothing else to test!
      return true;
    }
    // If there is nothing in the rectangle between the vector that is going to
    // move, and the place it is moving to, then they can be merged.
    // Setup a vertical search for any blob.
    const TabVector* mover = (IsRightTab() &&
       sort_key_ < other.sort_key_) ? this : &other;
    int top_y = mover->endpt_.y();
    int bottom_y = mover->startpt_.y();
    int left = MIN(mover->XAtY(top_y), mover->XAtY(bottom_y));
    int right = MAX(mover->XAtY(top_y), mover->XAtY(bottom_y));
    int shift = abs(sort_key_ - other.sort_key_) / v_scale;
    if (IsRightTab()) {
      right += shift;
    } else {
      left -= shift;
    }

    GridSearch<BLOBNBOX, BLOBNBOX_CLIST, BLOBNBOX_C_IT> vsearch(grid);
    vsearch.StartVerticalSearch(left, right, top_y);
    BLOBNBOX* blob;
    while ((blob = vsearch.NextVerticalSearch(true)) != NULL) {
      TBOX box = blob->bounding_box();
      if (box.top() > bottom_y)
        return true;  // Nothing found.
      if (box.bottom() < top_y)
        continue;  // Doesn't overlap.
      int left_at_box = XAtY(box.bottom());
      int right_at_box = left_at_box;
      if (IsRightTab())
        right_at_box += shift;
      else
        left_at_box -= shift;
      if (MIN(right_at_box, box.right()) > MAX(left_at_box, box.left()))
        return false;
    }
    return true;  // Nothing found.
  }
  return false;
}