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colpartitionset.cpp
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1 
2 // File: colpartitionset.cpp
3 // Description: Class to hold a list of ColPartitions of the page that
4 // correspond roughly to columns.
5 // Author: Ray Smith
6 // Created: Thu Aug 14 10:54:01 PDT 2008
7 //
8 // (C) Copyright 2008, Google Inc.
9 // Licensed under the Apache License, Version 2.0 (the "License");
10 // you may not use this file except in compliance with the License.
11 // You may obtain a copy of the License at
12 // http://www.apache.org/licenses/LICENSE-2.0
13 // Unless required by applicable law or agreed to in writing, software
14 // distributed under the License is distributed on an "AS IS" BASIS,
15 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 // See the License for the specific language governing permissions and
17 // limitations under the License.
18 //
20 
21 #include "colpartitionset.h"
22 #include "ndminx.h"
23 #include "workingpartset.h"
24 #include "tablefind.h"
25 
26 namespace tesseract {
27 
28 // Minimum width of a column to be interesting as a multiple of resolution.
29 const double kMinColumnWidth = 2.0 / 3;
30 
31 ELISTIZE(ColPartitionSet)
32 
33 ColPartitionSet::ColPartitionSet(ColPartition_LIST* partitions) {
34  ColPartition_IT it(&parts_);
35  it.add_list_after(partitions);
36  ComputeCoverage();
37 }
38 
40  ColPartition_IT it(&parts_);
41  it.add_after_then_move(part);
42  ComputeCoverage();
43 }
44 
46 }
47 
48 // Return an element of the parts_ list from its index.
50  ColPartition_IT it(&parts_);
51  it.mark_cycle_pt();
52  for (int i = 0; i < index && !it.cycled_list(); ++i, it.forward());
53  if (it.cycled_list())
54  return NULL;
55  return it.data();
56 }
57 
58 // Return the ColPartition that contains the given coords, if any, else NULL.
60  ColPartition_IT it(&parts_);
61  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
62  ColPartition* part = it.data();
63  if (part->ColumnContains(x, y))
64  return part;
65  }
66  return NULL;
67 }
68 
69 // Extract all the parts from the list, relinquishing ownership.
71  ColPartition_IT it(&parts_);
72  while (!it.empty()) {
73  it.extract();
74  it.forward();
75  }
76 }
77 
78 // Attempt to improve this by adding partitions or expanding partitions.
80  PartSetVector* src_sets) {
81  int set_size = src_sets->size();
82  // Iterate over the provided column sets, as each one may have something
83  // to improve this.
84  for (int i = 0; i < set_size; ++i) {
85  ColPartitionSet* column_set = src_sets->get(i);
86  if (column_set == NULL)
87  continue;
88  // Iterate over the parts in this and column_set, adding bigger or
89  // new parts in column_set to this.
90  ColPartition_IT part_it(&parts_);
91  ASSERT_HOST(!part_it.empty());
92  int prev_right = MIN_INT32;
93  part_it.mark_cycle_pt();
94  ColPartition_IT col_it(&column_set->parts_);
95  for (col_it.mark_cycle_pt(); !col_it.cycled_list(); col_it.forward()) {
96  ColPartition* col_part = col_it.data();
97  if (col_part->blob_type() < BRT_UNKNOWN)
98  continue; // Ignore image partitions.
99  int col_left = col_part->left_key();
100  int col_right = col_part->right_key();
101  // Sync-up part_it (in this) so it matches the col_part in column_set.
102  ColPartition* part = part_it.data();
103  while (!part_it.at_last() && part->right_key() < col_left) {
104  prev_right = part->right_key();
105  part_it.forward();
106  part = part_it.data();
107  }
108  int part_left = part->left_key();
109  int part_right = part->right_key();
110  if (part_right < col_left || col_right < part_left) {
111  // There is no overlap so this is a new partition.
112  AddPartition(col_part->ShallowCopy(), &part_it);
113  continue;
114  }
115  // Check the edges of col_part to see if they can improve part.
116  bool part_width_ok = cb->Run(part->KeyWidth(part_left, part_right));
117  if (col_left < part_left && col_left > prev_right) {
118  // The left edge of the column is better and it doesn't overlap,
119  // so we can potentially expand it.
120  int col_box_left = col_part->BoxLeftKey();
121  bool tab_width_ok = cb->Run(part->KeyWidth(col_left, part_right));
122  bool box_width_ok = cb->Run(part->KeyWidth(col_box_left, part_right));
123  if (tab_width_ok || (!part_width_ok )) {
124  // The tab is leaving the good column metric at least as good as
125  // it was before, so use the tab.
126  part->CopyLeftTab(*col_part, false);
127  part->SetColumnGoodness(cb);
128  } else if (col_box_left < part_left &&
129  (box_width_ok || !part_width_ok)) {
130  // The box is leaving the good column metric at least as good as
131  // it was before, so use the box.
132  part->CopyLeftTab(*col_part, true);
133  part->SetColumnGoodness(cb);
134  }
135  part_left = part->left_key();
136  }
137  if (col_right > part_right &&
138  (part_it.at_last() ||
139  part_it.data_relative(1)->left_key() > col_right)) {
140  // The right edge is better, so we can possibly expand it.
141  int col_box_right = col_part->BoxRightKey();
142  bool tab_width_ok = cb->Run(part->KeyWidth(part_left, col_right));
143  bool box_width_ok = cb->Run(part->KeyWidth(part_left, col_box_right));
144  if (tab_width_ok || (!part_width_ok )) {
145  // The tab is leaving the good column metric at least as good as
146  // it was before, so use the tab.
147  part->CopyRightTab(*col_part, false);
148  part->SetColumnGoodness(cb);
149  } else if (col_box_right > part_right &&
150  (box_width_ok || !part_width_ok)) {
151  // The box is leaving the good column metric at least as good as
152  // it was before, so use the box.
153  part->CopyRightTab(*col_part, true);
154  part->SetColumnGoodness(cb);
155  }
156  }
157  }
158  }
159  ComputeCoverage();
160 }
161 
162 // If this set is good enough to represent a new partitioning into columns,
163 // add it to the vector of sets, otherwise delete it.
165  WidthCallback* cb) {
166  bool debug = TabFind::WithinTestRegion(2, bounding_box_.left(),
167  bounding_box_.bottom());
168  if (debug) {
169  tprintf("Considering new column candidate:\n");
170  Print();
171  }
172  if (!LegalColumnCandidate()) {
173  if (debug) {
174  tprintf("Not a legal column candidate:\n");
175  Print();
176  }
177  delete this;
178  return;
179  }
180  for (int i = 0; i < column_sets->size(); ++i) {
181  ColPartitionSet* columns = column_sets->get(i);
182  // In ordering the column set candidates, good_coverage_ is king,
183  // followed by good_column_count_ and then bad_coverage_.
184  bool better = good_coverage_ > columns->good_coverage_;
185  if (good_coverage_ == columns->good_coverage_) {
186  better = good_column_count_ > columns->good_column_count_;
187  if (good_column_count_ == columns->good_column_count_) {
188  better = bad_coverage_ > columns->bad_coverage_;
189  }
190  }
191  if (better) {
192  // The new one is better so add it.
193  if (debug)
194  tprintf("Good one\n");
195  column_sets->insert(this, i);
196  return;
197  }
198  if (columns->CompatibleColumns(false, this, cb)) {
199  if (debug)
200  tprintf("Duplicate\n");
201  delete this;
202  return; // It is not unique.
203  }
204  }
205  if (debug)
206  tprintf("Added to end\n");
207  column_sets->push_back(this);
208 }
209 
210 // Return true if the partitions in other are all compatible with the columns
211 // in this.
213  WidthCallback* cb) {
214  if (debug) {
215  tprintf("CompatibleColumns testing compatibility\n");
216  Print();
217  other->Print();
218  }
219  if (other->parts_.empty()) {
220  if (debug)
221  tprintf("CompatibleColumns true due to empty other\n");
222  return true;
223  }
224  ColPartition_IT it(&other->parts_);
225  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
226  ColPartition* part = it.data();
227  if (part->blob_type() < BRT_UNKNOWN) {
228  if (debug) {
229  tprintf("CompatibleColumns ignoring image partition\n");
230  part->Print();
231  }
232  continue; // Image partitions are irrelevant to column compatibility.
233  }
234  int y = part->MidY();
235  int left = part->bounding_box().left();
236  int right = part->bounding_box().right();
237  ColPartition* left_col = ColumnContaining(left, y);
238  ColPartition* right_col = ColumnContaining(right, y);
239  if (right_col == NULL || left_col == NULL) {
240  if (debug) {
241  tprintf("CompatibleColumns false due to partition edge outside\n");
242  part->Print();
243  }
244  return false; // A partition edge lies outside of all columns
245  }
246  if (right_col != left_col && cb->Run(right - left)) {
247  if (debug) {
248  tprintf("CompatibleColumns false due to good width in multiple cols\n");
249  part->Print();
250  }
251  return false; // Partition with a good width must be in a single column.
252  }
253 
254  ColPartition_IT it2= it;
255  while (!it2.at_last()) {
256  it2.forward();
257  ColPartition* next_part = it2.data();
258  if (!BLOBNBOX::IsTextType(next_part->blob_type()))
259  continue; // Non-text partitions are irrelevant.
260  int next_left = next_part->bounding_box().left();
261  if (next_left == right) {
262  break; // They share the same edge, so one must be a pull-out.
263  }
264  // Search to see if right and next_left fall within a single column.
265  ColPartition* next_left_col = ColumnContaining(next_left, y);
266  if (right_col == next_left_col) {
267  // There is a column break in this column.
268  // This can be due to a figure caption within a column, a pull-out
269  // block, or a simple broken textline that remains to be merged:
270  // all allowed, or a change in column layout: not allowed.
271  // If both partitions are of good width, then it is likely
272  // a change in column layout, otherwise probably an allowed situation.
273  if (part->good_width() && next_part->good_width()) {
274  if (debug) {
275  int next_right = next_part->bounding_box().right();
276  tprintf("CompatibleColumns false due to 2 parts of good width\n");
277  tprintf("part1 %d-%d, part2 %d-%d\n",
278  left, right, next_left, next_right);
279  right_col->Print();
280  }
281  return false;
282  }
283  }
284  break;
285  }
286  }
287  if (debug)
288  tprintf("CompatibleColumns true!\n");
289  return true;
290 }
291 
292 // Returns the total width of all blobs in the part_set that do not lie
293 // within an approved column. Used as a cost measure for using this
294 // column set over another that might be compatible.
296  int total_width = 0;
297  ColPartition_IT it(&part_set->parts_);
298  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
299  ColPartition* part = it.data();
300  if (!BLOBNBOX::IsTextType(part->blob_type())) {
301  continue; // Non-text partitions are irrelevant to column compatibility.
302  }
303  int y = part->MidY();
304  BLOBNBOX_C_IT box_it(part->boxes());
305  for (box_it.mark_cycle_pt(); !box_it.cycled_list(); box_it.forward()) {
306  const TBOX& box = it.data()->bounding_box();
307  // Assume that the whole blob is outside any column iff its x-middle
308  // is outside.
309  int x = (box.left() + box.right()) / 2;
310  ColPartition* col = ColumnContaining(x, y);
311  if (col == NULL)
312  total_width += box.width();
313  }
314  }
315  return total_width;
316 }
317 
318 // Return true if this ColPartitionSet makes a legal column candidate by
319 // having legal individual partitions and non-overlapping adjacent pairs.
321  ColPartition_IT it(&parts_);
322  if (it.empty())
323  return false;
324  bool any_text_parts = false;
325  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
326  ColPartition* part = it.data();
327  if (BLOBNBOX::IsTextType(part->blob_type())) {
328  if (!part->IsLegal())
329  return false; // Individual partition is illegal.
330  any_text_parts = true;
331  }
332  if (!it.at_last()) {
333  ColPartition* next_part = it.data_relative(1);
334  if (next_part->left_key() < part->right_key()) {
335  return false;
336  }
337  }
338  }
339  return any_text_parts;
340 }
341 
342 // Return a copy of this. If good_only will only copy the Good ColPartitions.
344  ColPartition_LIST copy_parts;
345  ColPartition_IT src_it(&parts_);
346  ColPartition_IT dest_it(&copy_parts);
347  for (src_it.mark_cycle_pt(); !src_it.cycled_list(); src_it.forward()) {
348  ColPartition* part = src_it.data();
349  if (BLOBNBOX::IsTextType(part->blob_type()) &&
350  (!good_only || part->good_width() || part->good_column()))
351  dest_it.add_after_then_move(part->ShallowCopy());
352  }
353  if (dest_it.empty())
354  return NULL;
355  return new ColPartitionSet(&copy_parts);
356 }
357 
358 // Return the bounding boxes of columns at the given y-range
359 void ColPartitionSet::GetColumnBoxes(int y_bottom, int y_top,
360  ColSegment_LIST *segments) {
361  ColPartition_IT it(&parts_);
362  ColSegment_IT col_it(segments);
363  col_it.move_to_last();
364  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
365  ColPartition* part = it.data();
366  ICOORD bot_left(part->LeftAtY(y_top), y_bottom);
367  ICOORD top_right(part->RightAtY(y_bottom), y_top);
368  ColSegment *col_seg = new ColSegment();
369  col_seg->InsertBox(TBOX(bot_left, top_right));
370  col_it.add_after_then_move(col_seg);
371  }
372 }
373 
374 // Display the edges of the columns at the given y coords.
375 void ColPartitionSet::DisplayColumnEdges(int y_bottom, int y_top,
376  ScrollView* win) {
377  #ifndef GRAPHICS_DISABLED
378  ColPartition_IT it(&parts_);
379  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
380  ColPartition* part = it.data();
381  win->Line(part->LeftAtY(y_top), y_top, part->LeftAtY(y_bottom), y_bottom);
382  win->Line(part->RightAtY(y_top), y_top, part->RightAtY(y_bottom), y_bottom);
383  }
384  #endif // GRAPHICS_DISABLED
385 }
386 
387 // Return the ColumnSpanningType that best explains the columns overlapped
388 // by the given coords(left,right,y), with the given margins.
389 // Also return the first and last column index touched by the coords and
390 // the leftmost spanned column.
391 // Column indices are 2n + 1 for real columns (0 based) and even values
392 // represent the gaps in between columns, with 0 being left of the leftmost.
393 // resolution refers to the ppi resolution of the image.
395  int left, int right, int y,
396  int left_margin,
397  int right_margin,
398  int* first_col,
399  int* last_col,
400  int* first_spanned_col) {
401  *first_col = -1;
402  *last_col = -1;
403  *first_spanned_col = -1;
404  int margin_columns = 0;
405  ColPartition_IT it(&parts_);
406  int col_index = 1;
407  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward(), col_index += 2) {
408  ColPartition* part = it.data();
409  if (part->ColumnContains(left, y)) {
410  // In the default case, first_col is set, but columns_spanned remains
411  // zero, so first_col will get reset in the first column genuinely
412  // spanned, but we can tell the difference from a noise partition
413  // that touches no column.
414  *first_col = col_index;
415  if (part->ColumnContains(right, y)) {
416  // Both within a single column.
417  *last_col = col_index;
418  return CST_FLOWING;
419  }
420  if (left_margin <= part->LeftAtY(y)) {
421  // It completely spans this column.
422  *first_spanned_col = col_index;
423  margin_columns = 1;
424  }
425  } else if (part->ColumnContains(right, y)) {
426  if (*first_col < 0) {
427  // It started in-between.
428  *first_col = col_index - 1;
429  }
430  if (right_margin >= part->RightAtY(y)) {
431  // It completely spans this column.
432  if (margin_columns == 0)
433  *first_spanned_col = col_index;
434  ++margin_columns;
435  }
436  *last_col = col_index;
437  break;
438  } else if (left < part->LeftAtY(y) && right > part->RightAtY(y)) {
439  // Neither left nor right are contained within, so it spans this
440  // column.
441  if (*first_col < 0) {
442  // It started in between the previous column and the current column.
443  *first_col = col_index - 1;
444  }
445  if (margin_columns == 0)
446  *first_spanned_col = col_index;
447  *last_col = col_index;
448  } else if (right < part->LeftAtY(y)) {
449  // We have gone past the end.
450  *last_col = col_index - 1;
451  if (*first_col < 0) {
452  // It must lie completely between columns =>noise.
453  *first_col = col_index - 1;
454  }
455  break;
456  }
457  }
458  if (*first_col < 0)
459  *first_col = col_index - 1; // The last in-between.
460  if (*last_col < 0)
461  *last_col = col_index - 1; // The last in-between.
462  ASSERT_HOST(*first_col >= 0 && *last_col >= 0);
463  ASSERT_HOST(*first_col <= *last_col);
464  if (*first_col == *last_col && right - left < kMinColumnWidth * resolution) {
465  // Neither end was in a column, and it didn't span any, so it lies
466  // entirely between columns, therefore noise.
467  return CST_NOISE;
468  } else if (margin_columns <= 1) {
469  // An exception for headings that stick outside of single-column text.
470  if (margin_columns == 1 && parts_.singleton()) {
471  return CST_HEADING;
472  }
473  // It is a pullout, as left and right were not in the same column, but
474  // it doesn't go to the edge of its start and end.
475  return CST_PULLOUT;
476  }
477  // Its margins went to the edges of first and last columns => heading.
478  return CST_HEADING;
479 }
480 
481 // The column_set has changed. Close down all in-progress WorkingPartSets in
482 // columns that do not match and start new ones for the new columns in this.
483 // As ColPartitions are turned into BLOCKs, the used ones are put in
484 // used_parts, as they still need to be referenced in the grid.
486  const ICOORD& tright,
487  int resolution,
488  ColPartition_LIST* used_parts,
489  WorkingPartSet_LIST* working_set_list) {
490  // Move the input list to a temporary location so we can delete its elements
491  // as we add them to the output working_set.
492  WorkingPartSet_LIST work_src;
493  WorkingPartSet_IT src_it(&work_src);
494  src_it.add_list_after(working_set_list);
495  src_it.move_to_first();
496  WorkingPartSet_IT dest_it(working_set_list);
497  // Completed blocks and to_blocks are accumulated and given to the first new
498  // one whenever we keep a column, or at the end.
499  BLOCK_LIST completed_blocks;
500  TO_BLOCK_LIST to_blocks;
501  WorkingPartSet* first_new_set = NULL;
502  WorkingPartSet* working_set = NULL;
503  ColPartition_IT col_it(&parts_);
504  for (col_it.mark_cycle_pt(); !col_it.cycled_list(); col_it.forward()) {
505  ColPartition* column = col_it.data();
506  // Any existing column to the left of column is completed.
507  while (!src_it.empty() &&
508  ((working_set = src_it.data())->column() == NULL ||
509  working_set->column()->right_key() <= column->left_key())) {
510  src_it.extract();
511  working_set->ExtractCompletedBlocks(bleft, tright, resolution,
512  used_parts, &completed_blocks,
513  &to_blocks);
514  delete working_set;
515  src_it.forward();
516  }
517  // Make a new between-column WorkingSet for before the current column.
518  working_set = new WorkingPartSet(NULL);
519  dest_it.add_after_then_move(working_set);
520  if (first_new_set == NULL)
521  first_new_set = working_set;
522  // A matching column gets to stay, and first_new_set gets all the
523  // completed_sets.
524  working_set = src_it.empty() ? NULL : src_it.data();
525  if (working_set != NULL &&
526  working_set->column()->MatchingColumns(*column)) {
527  working_set->set_column(column);
528  dest_it.add_after_then_move(src_it.extract());
529  src_it.forward();
530  first_new_set->InsertCompletedBlocks(&completed_blocks, &to_blocks);
531  first_new_set = NULL;
532  } else {
533  // Just make a new working set for the current column.
534  working_set = new WorkingPartSet(column);
535  dest_it.add_after_then_move(working_set);
536  }
537  }
538  // Complete any remaining src working sets.
539  while (!src_it.empty()) {
540  working_set = src_it.extract();
541  working_set->ExtractCompletedBlocks(bleft, tright, resolution,
542  used_parts, &completed_blocks,
543  &to_blocks);
544  delete working_set;
545  src_it.forward();
546  }
547  // Make a new between-column WorkingSet for after the last column.
548  working_set = new WorkingPartSet(NULL);
549  dest_it.add_after_then_move(working_set);
550  if (first_new_set == NULL)
551  first_new_set = working_set;
552  // The first_new_set now gets any accumulated completed_parts/blocks.
553  first_new_set->InsertCompletedBlocks(&completed_blocks, &to_blocks);
554 }
555 
556 // Accumulate the widths and gaps into the given variables.
558  int* width_samples,
559  int* total_gap,
560  int* gap_samples) {
561  ColPartition_IT it(&parts_);
562  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
563  ColPartition* part = it.data();
564  *total_width += part->ColumnWidth();
565  ++*width_samples;
566  if (!it.at_last()) {
567  ColPartition* next_part = it.data_relative(1);
568  int gap = part->KeyWidth(part->right_key(), next_part->left_key());
569  *total_gap += gap;
570  ++*gap_samples;
571  }
572  }
573 }
574 
575 // Provide debug output for this ColPartitionSet and all the ColPartitions.
577  ColPartition_IT it(&parts_);
578  tprintf("Partition set of %d parts, %d good, coverage=%d+%d"
579  " (%d,%d)->(%d,%d)\n",
580  it.length(), good_column_count_, good_coverage_, bad_coverage_,
581  bounding_box_.left(), bounding_box_.bottom(),
582  bounding_box_.right(), bounding_box_.top());
583  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
584  ColPartition* part = it.data();
585  part->Print();
586  }
587 }
588 
589 // PRIVATE CODE.
590 
591 // Add the given partition to the list in the appropriate place.
592 void ColPartitionSet::AddPartition(ColPartition* new_part,
593  ColPartition_IT* it) {
594  AddPartitionCoverageAndBox(*new_part);
595  int new_right = new_part->right_key();
596  if (it->data()->left_key() >= new_right)
597  it->add_before_stay_put(new_part);
598  else
599  it->add_after_stay_put(new_part);
600 }
601 
602 // Compute the coverage and good column count. Coverage is the amount of the
603 // width of the page (in pixels) that is covered by ColPartitions, which are
604 // used to provide candidate column layouts.
605 // Coverage is split into good and bad. Good coverage is provided by
606 // ColPartitions of a frequent width (according to the callback function
607 // provided by TabFinder::WidthCB, which accesses stored statistics on the
608 // widths of ColParititions) and bad coverage is provided by all other
609 // ColPartitions, even if they have tab vectors at both sides. Thus:
610 // |-----------------------------------------------------------------|
611 // | Double width heading |
612 // |-----------------------------------------------------------------|
613 // |-------------------------------| |-------------------------------|
614 // | Common width ColParition | | Common width ColPartition |
615 // |-------------------------------| |-------------------------------|
616 // the layout with two common-width columns has better coverage than the
617 // double width heading, because the coverage is "good," even though less in
618 // total coverage than the heading, because the heading coverage is "bad."
619 void ColPartitionSet::ComputeCoverage() {
620  // Count the number of good columns and sum their width.
621  ColPartition_IT it(&parts_);
622  good_column_count_ = 0;
623  good_coverage_ = 0;
624  bad_coverage_ = 0;
625  bounding_box_ = TBOX();
626  for (it.mark_cycle_pt(); !it.cycled_list(); it.forward()) {
627  ColPartition* part = it.data();
628  AddPartitionCoverageAndBox(*part);
629  }
630 }
631 
632 // Adds the coverage, column count and box for a single partition,
633 // without adding it to the list. (Helper factored from ComputeCoverage.)
634 void ColPartitionSet::AddPartitionCoverageAndBox(const ColPartition& part) {
635  bounding_box_ += part.bounding_box();
636  int coverage = part.ColumnWidth();
637  if (part.good_width()) {
638  good_coverage_ += coverage;
639  good_column_count_ += 2;
640  } else {
641  if (part.blob_type() < BRT_UNKNOWN)
642  coverage /= 2;
643  if (part.good_column())
644  ++good_column_count_;
645  bad_coverage_ += coverage;
646  }
647 }
648 
649 } // namespace tesseract.