tesseract  5.0.0
colfind.h
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1 // File: colfind.h
3 // Description: Class to find columns in the grid of BLOBNBOXes.
4 // Author: Ray Smith
5 //
6 // (C) Copyright 2008, Google Inc.
7 // Licensed under the Apache License, Version 2.0 (the "License");
8 // you may not use this file except in compliance with the License.
9 // You may obtain a copy of the License at
10 // http://www.apache.org/licenses/LICENSE-2.0
11 // Unless required by applicable law or agreed to in writing, software
12 // distributed under the License is distributed on an "AS IS" BASIS,
13 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 // See the License for the specific language governing permissions and
15 // limitations under the License.
16 //
18 
19 #ifndef TESSERACT_TEXTORD_COLFIND_H_
20 #define TESSERACT_TEXTORD_COLFIND_H_
21 
22 #include "colpartitiongrid.h"
23 #include "colpartitionset.h"
24 #include "debugpixa.h"
25 #include "imagefind.h"
26 #include "ocrblock.h"
27 #include "tabfind.h"
28 #include "textlineprojection.h"
29 
30 class BLOCK_LIST;
31 struct Boxa;
32 struct Pixa;
33 class DENORM;
34 class ScrollView;
35 class STATS;
36 class TO_BLOCK;
37 
38 namespace tesseract {
39 
40 class ColPartitionSet;
41 class ColPartitionSet_LIST;
42 class ColSegment_LIST;
43 class ColumnGroup_LIST;
44 class LineSpacing;
45 class StrokeWidth;
46 class TempColumn_LIST;
47 class EquationDetectBase;
48 
49 // The ColumnFinder class finds columns in the grid.
50 class TESS_API ColumnFinder : public TabFind {
51 public:
52  // Gridsize is an estimate of the text size in the image. A suitable value
53  // is in TO_BLOCK::line_size after find_components has been used to make
54  // the blobs.
55  // bleft and tright are the bounds of the image (rectangle) being processed.
56  // vlines is a (possibly empty) list of TabVector and vertical_x and y are
57  // the sum logical vertical vector produced by LineFinder::FindVerticalLines.
58  // If cjk_script is true, then broken CJK characters are fixed during
59  // layout analysis to assist in detecting horizontal vs vertically written
60  // textlines.
61  ColumnFinder(int gridsize, const ICOORD &bleft, const ICOORD &tright, int resolution,
62  bool cjk_script, double aligned_gap_fraction, TabVector_LIST *vlines,
63  TabVector_LIST *hlines, int vertical_x, int vertical_y);
64  ~ColumnFinder() override;
65 
66  // Accessors for testing
67  const DENORM *denorm() const {
68  return denorm_;
69  }
70  const TextlineProjection *projection() const {
71  return &projection_;
72  }
73  void set_cjk_script(bool is_cjk) {
74  cjk_script_ = is_cjk;
75  }
76 
77  // ======================================================================
78  // The main function of ColumnFinder is broken into pieces to facilitate
79  // optional insertion of orientation and script detection in an efficient
80  // way. The calling sequence IS MANDATORY however, whether or not
81  // OSD is being used:
82  // 1. Construction.
83  // 2. SetupAndFilterNoise.
84  // 3. IsVerticallyAlignedText.
85  // 4. CorrectOrientation.
86  // 5. FindBlocks.
87  // 6. Destruction. Use of a single column finder for multiple images does not
88  // make sense.
89  // Throughout these steps, the ColPartitions are owned by part_grid_, which
90  // means that that it must be kept correct. Exception: big_parts_ owns its
91  // own ColPartitions.
92  // The BLOBNBOXes are owned by the input TO_BLOCK for the whole time, except
93  // for a phase in FindBlocks before TransformToBlocks, when they become
94  // owned by the ColPartitions. The owner() ColPartition of a BLOBNBOX
95  // indicates more of a betrothal for the majority of layout analysis, ie
96  // which ColPartition will take ownership when the blobs are release from
97  // the input TO_BLOCK. Exception: image_bblobs_ owns the fake blobs that
98  // are part of the image regions, as they are not on any TO_BLOCK list.
99  // TODO(rays) break up column finder further into smaller classes, as
100  // there is a lot more to it than column finding now.
101  // ======================================================================
102 
103  // Performs initial processing on the blobs in the input_block:
104  // Setup the part_grid, stroke_width_, nontext_map_.
105  // Obvious noise blobs are filtered out and used to mark the nontext_map_.
106  // Initial stroke-width analysis is used to get local text alignment
107  // direction, so the textline projection_ map can be setup.
108  // On return, IsVerticallyAlignedText may be called (now optionally) to
109  // determine the gross textline alignment of the page.
110  void SetupAndFilterNoise(PageSegMode pageseg_mode, Image photo_mask_pix, TO_BLOCK *input_block);
111 
112  // Tests for vertical alignment of text (returning true if so), and generates
113  // a list of blobs (in osd_blobs) for orientation and script detection.
114  // block is the single block for the whole page or rectangle to be OCRed.
115  // Note that the vertical alignment may be due to text whose writing direction
116  // is vertical, like say Japanese, or due to text whose writing direction is
117  // horizontal but whose text appears vertically aligned because the image is
118  // not the right way up.
119  // find_vertical_text_ratio should be textord_tabfind_vertical_text_ratio.
120  bool IsVerticallyAlignedText(double find_vertical_text_ratio, TO_BLOCK *block,
121  BLOBNBOX_CLIST *osd_blobs);
122 
123  // Rotates the blobs and the TabVectors so that the gross writing direction
124  // (text lines) are horizontal and lines are read down the page.
125  // Applied rotation stored in rotation_.
126  // A second rotation is calculated for application during recognition to
127  // make the rotated blobs upright for recognition.
128  // Subsequent rotation stored in text_rotation_.
129  //
130  // Arguments:
131  // vertical_text_lines is true if the text lines are vertical.
132  // recognition_rotation [0..3] is the number of anti-clockwise 90 degree
133  // rotations from osd required for the text to be upright and readable.
134  void CorrectOrientation(TO_BLOCK *block, bool vertical_text_lines, int recognition_rotation);
135 
136  // Finds blocks of text, image, rule line, table etc, returning them in the
137  // blocks and to_blocks
138  // (Each TO_BLOCK points to the basic BLOCK and adds more information.)
139  // Image blocks are generated by a combination of photo_mask_pix (which may
140  // NOT be nullptr) and the rejected text found during preliminary textline
141  // finding.
142  // The input_block is the result of a call to find_components, and contains
143  // the blobs found in the image or rectangle to be OCRed. These blobs will be
144  // removed and placed in the output blocks, while unused ones will be deleted.
145  // If single_column is true, the input is treated as single column, but
146  // it is still divided into blocks of equal line spacing/text size.
147  // scaled_color is scaled down by scaled_factor from the input color image,
148  // and may be nullptr if the input was not color.
149  // grey_pix is optional, but if present must match the photo_mask_pix in size,
150  // and must be a *real* grey image instead of binary_pix * 255.
151  // thresholds_pix is expected to be present iff grey_pix is present and
152  // can be an integer factor reduction of the grey_pix. It represents the
153  // thresholds that were used to create the binary_pix from the grey_pix.
154  // Small blobs that confuse the segmentation into lines are placed into
155  // diacritic_blobs, with the intention that they be put into the most
156  // appropriate word after the rest of layout analysis.
157  // Returns -1 if the user hits the 'd' key in the blocks window while running
158  // in debug mode, which requests a retry with more debug info.
159  int FindBlocks(PageSegMode pageseg_mode, Image scaled_color, int scaled_factor, TO_BLOCK *block,
160  Image photo_mask_pix, Image thresholds_pix, Image grey_pix, DebugPixa *pixa_debug,
161  BLOCK_LIST *blocks, BLOBNBOX_LIST *diacritic_blobs, TO_BLOCK_LIST *to_blocks);
162 
163  // Get the rotation required to deskew, and its inverse rotation.
164  void GetDeskewVectors(FCOORD *deskew, FCOORD *reskew);
165 
166  // Set the equation detection pointer.
167  void SetEquationDetect(EquationDetectBase *detect);
168 
169 private:
170  // Displays the blob and block bounding boxes in a window called Blocks.
171  void DisplayBlocks(BLOCK_LIST *blocks);
172  // Displays the column edges at each grid y coordinate defined by
173  // best_columns_.
174  void DisplayColumnBounds(PartSetVector *sets);
175 
177 
178  // Sets up column_sets_ (the determined column layout at each horizontal
179  // slice). Returns false if the page is empty.
180  bool MakeColumns(bool single_column);
181  // Attempt to improve the column_candidates by expanding the columns
182  // and adding new partitions from the partition sets in src_sets.
183  // Src_sets may be equal to column_candidates, in which case it will
184  // use them as a source to improve themselves.
185  void ImproveColumnCandidates(PartSetVector *src_sets, PartSetVector *column_sets);
186  // Prints debug information on the column candidates.
187  void PrintColumnCandidates(const char *title);
188  // Finds the optimal set of columns that cover the entire image with as
189  // few changes in column partition as possible.
190  // Returns true if any part of the page is multi-column.
191  bool AssignColumns(const PartSetVector &part_sets);
192  // Finds the biggest range in part_sets_ that has no assigned column, but
193  // column assignment is possible.
194  bool BiggestUnassignedRange(int set_count, const bool *any_columns_possible, int *start,
195  int *end);
196  // Finds the modal compatible column_set_ index within the given range.
197  int RangeModalColumnSet(int **column_set_costs, const int *assigned_costs, int start, int end);
198  // Given that there are many column_set_id compatible columns in the range,
199  // shrinks the range to the longest contiguous run of compatibility, allowing
200  // gaps where no columns are possible, but not where competing columns are
201  // possible.
202  void ShrinkRangeToLongestRun(int **column_set_costs, const int *assigned_costs,
203  const bool *any_columns_possible, int column_set_id, int *best_start,
204  int *best_end);
205  // Moves start in the direction of step, up to, but not including end while
206  // the only incompatible regions are no more than kMaxIncompatibleColumnCount
207  // in size, and the compatible regions beyond are bigger.
208  void ExtendRangePastSmallGaps(int **column_set_costs, const int *assigned_costs,
209  const bool *any_columns_possible, int column_set_id, int step,
210  int end, int *start);
211  // Assigns the given column_set_id to the part_sets_ in the given range.
212  void AssignColumnToRange(int column_set_id, int start, int end, int **column_set_costs,
213  int *assigned_costs);
214 
215  // Computes the mean_column_gap_.
216  void ComputeMeanColumnGap(bool any_multi_column);
217 
220 
221  // Hoovers up all un-owned blobs and deletes them.
222  // The rest get released from the block so the ColPartitions can pass
223  // ownership to the output blocks.
224  void ReleaseBlobsAndCleanupUnused(TO_BLOCK *block);
225  // Splits partitions that cross columns where they have nothing in the gap.
226  void GridSplitPartitions();
227  // Merges partitions where there is vertical overlap, within a single column,
228  // and the horizontal gap is small enough.
229  void GridMergePartitions();
230  // Inserts remaining noise blobs into the most applicable partition if any.
231  // If there is no applicable partition, then the blobs are deleted.
232  void InsertRemainingNoise(TO_BLOCK *block);
233  // Remove partitions that come from horizontal lines that look like
234  // underlines, but are not part of a table.
235  void GridRemoveUnderlinePartitions();
236  // Add horizontal line separators as partitions.
237  void GridInsertHLinePartitions();
238  // Add vertical line separators as partitions.
239  void GridInsertVLinePartitions();
240  // For every ColPartition in the grid, sets its type based on position
241  // in the columns.
242  void SetPartitionTypes();
243  // Only images remain with multiple types in a run of partners.
244  // Sets the type of all in the group to the maximum of the group.
245  void SmoothPartnerRuns();
246 
248 
249  // Helper functions for TransformToBlocks.
250  // Add the part to the temp list in the correct order.
251  void AddToTempPartList(ColPartition *part, ColPartition_CLIST *temp_list);
252  // Add everything from the temp list to the work_set assuming correct order.
253  void EmptyTempPartList(ColPartition_CLIST *temp_list, WorkingPartSet_LIST *work_set);
254 
255  // Transform the grid of partitions to the output blocks.
256  void TransformToBlocks(BLOCK_LIST *blocks, TO_BLOCK_LIST *to_blocks);
257 
258  // Reflect the blob boxes (but not the outlines) in the y-axis so that
259  // the blocks get created in the correct RTL order. Rotates the blobs
260  // in the input_block and the bblobs list.
261  // The reflection is undone in RotateAndReskewBlocks by
262  // reflecting the blocks themselves, and then recomputing the blob bounding
263  // boxes.
264  void ReflectForRtl(TO_BLOCK *input_block, BLOBNBOX_LIST *bblobs);
265 
266  // Undo the deskew that was done in FindTabVectors, as recognition is done
267  // without correcting blobs or blob outlines for skew.
268  // Reskew the completed blocks to put them back to the original rotated coords
269  // that were created by CorrectOrientation.
270  // If the input_is_rtl, then reflect the blocks in the y-axis to undo the
271  // reflection that was done before FindTabVectors.
272  // Blocks that were identified as vertical text (relative to the rotated
273  // coordinates) are further rotated so the text lines are horizontal.
274  // blob polygonal outlines are rotated to match the position of the blocks
275  // that they are in, and their bounding boxes are recalculated to be accurate.
276  // Record appropriate inverse transformations and required
277  // classifier transformation in the blocks.
278  void RotateAndReskewBlocks(bool input_is_rtl, TO_BLOCK_LIST *to_blocks);
279 
280  // Computes the rotations for the block (to make textlines horizontal) and
281  // for the blobs (for classification) and sets the appropriate members
282  // of the given block.
283  // Returns the rotation that needs to be applied to the blobs to make
284  // them sit in the rotated block.
285  FCOORD ComputeBlockAndClassifyRotation(BLOCK *block);
286 
287  // If true then the page language is cjk, so it is safe to perform
288  // FixBrokenCJK.
289  bool cjk_script_;
290  // The minimum gutter width to apply for finding columns.
291  // Modified when vertical text is detected to prevent detection of
292  // vertical text lines as columns.
293  int min_gutter_width_;
294  // The mean gap between columns over the page.
295  int mean_column_gap_;
296  // Config param saved at construction time. Modifies min_gutter_width_ with
297  // vertical text to prevent detection of vertical text as columns.
298  double tabfind_aligned_gap_fraction_;
299  // The rotation vector needed to convert original coords to deskewed.
300  FCOORD deskew_;
301  // The rotation vector needed to convert deskewed back to original coords.
302  FCOORD reskew_;
303  // The rotation vector used to rotate vertically oriented pages.
304  FCOORD rotation_;
305  // The rotation vector needed to convert the rotated back to original coords.
306  FCOORD rerotate_;
307  // The additional rotation vector needed to rotate text for recognition.
308  FCOORD text_rotation_;
309  // The column_sets_ contain the ordered candidate ColPartitionSets that
310  // define the possible divisions of the page into columns.
311  PartSetVector column_sets_;
312  // A simple array of pointers to the best assigned column division at
313  // each grid y coordinate.
314  ColPartitionSet **best_columns_;
315  // The grid used for creating initial partitions with strokewidth.
316  StrokeWidth *stroke_width_;
317  // The grid used to hold ColPartitions after the columns have been determined.
318  ColPartitionGrid part_grid_;
319  // List of ColPartitions that are no longer needed after they have been
320  // turned into regions, but are kept around because they are referenced
321  // by the part_grid_.
322  ColPartition_LIST good_parts_;
323  // List of ColPartitions that are big and might be dropcap or vertically
324  // joined.
325  ColPartition_LIST big_parts_;
326  // List of ColPartitions that have been declared noise.
327  ColPartition_LIST noise_parts_;
328  // The fake blobs that are made from the images.
329  BLOBNBOX_LIST image_bblobs_;
330  // Horizontal line separators.
331  TabVector_LIST horizontal_lines_;
332  // Image map of photo/noise areas on the page.
333  Image nontext_map_;
334  // Textline projection map.
335  TextlineProjection projection_;
336  // Sequence of DENORMS that indicate how to get back to the original image
337  // coordinate space. The destructor must delete all the DENORMs in the chain.
338  DENORM *denorm_;
339 
340  // The equation region detector pointer. Note: This pointer is passed in by
341  // member function SetEquationDetect, and releasing it is NOT owned by this
342  // class.
343  EquationDetectBase *equation_detect_;
344 
345 #ifndef GRAPHICS_DISABLED
346  // Various debug windows that automatically go away on completion.
347  ScrollView *input_blobs_win_ = nullptr;
348 
349  // Allow a subsequent instance to reuse the blocks window.
350  // Not thread-safe, but multiple threads shouldn't be using windows anyway.
351  static ScrollView *blocks_win_;
352 #endif
353 };
354 
355 } // namespace tesseract.
356 
357 #endif // TESSERACT_TEXTORD_COLFIND_H_
std::vector< ColPartitionSet * > PartSetVector
integer coordinate
Definition: points.h:36
const TextlineProjection * projection() const
Definition: colfind.h:70
void set_cjk_script(bool is_cjk)
Definition: colfind.h:73
const DENORM * denorm() const
Definition: colfind.h:67
#define TESS_API
Definition: export.h:34