tesseract  5.0.0
boxchar.cpp
Go to the documentation of this file.
1 /**********************************************************************
2  * File: boxchar.cpp
3  * Description: Simple class to associate a Tesseract classification unit with
4  * its bounding box so that the boxes can be rotated as the image
5  * is rotated for degradation. Also includes routines to output
6  * the character-tagged boxes to a boxfile.
7  * Author: Ray Smith
8  *
9  * (C) Copyright 2013, Google Inc.
10  * Licensed under the Apache License, Version 2.0 (the "License");
11  * you may not use this file except in compliance with the License.
12  * You may obtain a copy of the License at
13  * http://www.apache.org/licenses/LICENSE-2.0
14  * Unless required by applicable law or agreed to in writing, software
15  * distributed under the License is distributed on an "AS IS" BASIS,
16  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17  * See the License for the specific language governing permissions and
18  * limitations under the License.
19  *
20  **********************************************************************/
21 
22 #include "boxchar.h"
23 
24 #include "fileio.h"
25 #include "normstrngs.h"
26 #include "tprintf.h"
27 #include "unicharset.h"
28 #include "unicode/uchar.h" // from libicu
29 
30 #include <algorithm>
31 #include <cstddef>
32 #include <vector>
33 
34 // Absolute Ratio of dx:dy or dy:dx to be a newline.
35 const int kMinNewlineRatio = 5;
36 
37 namespace tesseract {
38 
39 BoxChar::BoxChar(const char *utf8_str, int len)
40  : ch_(utf8_str, len), box_(nullptr), page_(0), rtl_index_(-1) {}
41 
43  boxDestroy(&box_);
44 }
45 
46 void BoxChar::AddBox(int x, int y, int width, int height) {
47  box_ = boxCreate(x, y, width, height);
48 }
49 
50 // Increments *num_rtl and *num_ltr according to the directionality of
51 // characters in the box.
52 void BoxChar::GetDirection(int *num_rtl, int *num_ltr) const {
53  // Convert the unichar to UTF32 representation
54  std::vector<char32> uni_vector = UNICHAR::UTF8ToUTF32(ch_.c_str());
55  if (uni_vector.empty()) {
56  tprintf("Illegal utf8 in boxchar string:%s = ", ch_.c_str());
57  for (char c : ch_) {
58  tprintf(" 0x%x", c);
59  }
60  tprintf("\n");
61  return;
62  }
63  for (char32 ch : uni_vector) {
64  UCharDirection dir = u_charDirection(ch);
65  if (dir == U_RIGHT_TO_LEFT || dir == U_RIGHT_TO_LEFT_ARABIC || dir == U_RIGHT_TO_LEFT_ISOLATE) {
66  ++*num_rtl;
67  } else if ((dir == U_ARABIC_NUMBER) ||
68  (dir != U_DIR_NON_SPACING_MARK && dir != U_BOUNDARY_NEUTRAL)) {
69  ++*num_ltr;
70  }
71  }
72 }
73 
74 // Reverses the order of unicodes within the box. If Pango generates a
75 // ligature, these will get reversed on output, so reverse now.
77  std::vector<char32> unicodes = UNICHAR::UTF8ToUTF32(ch_.c_str());
78  std::reverse(unicodes.begin(), unicodes.end());
79  ch_ = UNICHAR::UTF32ToUTF8(unicodes);
80 }
81 
82 /* static */
83 void BoxChar::TranslateBoxes(int xshift, int yshift, std::vector<BoxChar *> *boxes) {
84  for (auto &boxe : *boxes) {
85  BOX *box = boxe->box_;
86  if (box != nullptr) {
87  box->x += xshift;
88  box->y += yshift;
89  }
90  }
91 }
92 
93 // Prepares for writing the boxes to a file by inserting newlines, spaces,
94 // and re-ordering so the boxes are strictly left-to-right.
95 /* static */
96 void BoxChar::PrepareToWrite(std::vector<BoxChar *> *boxes) {
97  bool rtl_rules = ContainsMostlyRTL(*boxes);
98  bool vertical_rules = MostlyVertical(*boxes);
99  InsertNewlines(rtl_rules, vertical_rules, boxes);
100  InsertSpaces(rtl_rules, vertical_rules, boxes);
101  for (size_t i = 0; i < boxes->size(); ++i) {
102  if ((*boxes)[i]->box_ == nullptr) {
103  tprintf("Null box at index %zu\n", i);
104  }
105  }
106  if (rtl_rules) {
107  ReorderRTLText(boxes);
108  }
109 }
110 
111 // Inserts newline (tab) characters into the vector at newline positions.
112 /* static */
113 void BoxChar::InsertNewlines(bool rtl_rules, bool vertical_rules, std::vector<BoxChar *> *boxes) {
114  size_t prev_i = SIZE_MAX;
115  int max_shift = 0;
116  for (size_t i = 0; i < boxes->size(); ++i) {
117  Box *box = (*boxes)[i]->box_;
118  if (box == nullptr) {
119  if (prev_i == SIZE_MAX || prev_i + 1 < i || i + 1 == boxes->size()) {
120  // Erase null boxes at the start of a line and after another null box.
121  do {
122  delete (*boxes)[i];
123  boxes->erase(boxes->begin() + i);
124  if (i == 0) {
125  break;
126  }
127  } while (i-- == boxes->size() && (*boxes)[i]->box_ == nullptr);
128  }
129  continue;
130  }
131  if (prev_i != SIZE_MAX) {
132  Box *prev_box = (*boxes)[prev_i]->box_;
133  int shift = box->x - prev_box->x;
134  if (vertical_rules) {
135  shift = box->y - prev_box->y;
136  } else if (rtl_rules) {
137  shift = -shift;
138  }
139  if (-shift > max_shift) {
140  // This is a newline. Since nothing cares about the size of the box,
141  // except the out-of-bounds checker, minimize the chance of creating
142  // a box outside the image by making the width and height 1.
143  int width = 1;
144  int height = 1;
145  int x = prev_box->x + prev_box->w;
146  int y = prev_box->y;
147  if (vertical_rules) {
148  x = prev_box->x;
149  y = prev_box->y + prev_box->h;
150  } else if (rtl_rules) {
151  x = prev_box->x - width;
152  if (x < 0) {
153  tprintf("prev x = %d, width=%d\n", prev_box->x, width);
154  x = 0;
155  }
156  }
157  if (prev_i + 1 == i) {
158  // New character needed.
159  auto *new_box = new BoxChar("\t", 1);
160  new_box->AddBox(x, y, width, height);
161  new_box->page_ = (*boxes)[i]->page_;
162  boxes->insert(boxes->begin() + i, new_box);
163  ++i;
164  } else {
165  (*boxes)[i - 1]->AddBox(x, y, width, height);
166  (*boxes)[i - 1]->ch_ = "\t";
167  }
168  max_shift = 0;
169  } else if (shift > max_shift) {
170  max_shift = shift;
171  }
172  }
173  prev_i = i;
174  }
175 }
176 
177 // Converts nullptr boxes to space characters, with appropriate bounding boxes.
178 /* static */
179 void BoxChar::InsertSpaces(bool rtl_rules, bool vertical_rules, std::vector<BoxChar *> *boxes) {
180  // After InsertNewlines, any remaining null boxes are not newlines, and are
181  // singletons, so add a box to each remaining null box.
182  for (size_t i = 1; i + 1 < boxes->size(); ++i) {
183  Box *box = (*boxes)[i]->box_;
184  if (box == nullptr) {
185  Box *prev = (*boxes)[i - 1]->box_;
186  Box *next = (*boxes)[i + 1]->box_;
187  ASSERT_HOST(prev != nullptr && next != nullptr);
188  int top = std::min(prev->y, next->y);
189  int bottom = std::max(prev->y + prev->h, next->y + next->h);
190  int left = prev->x + prev->w;
191  int right = next->x;
192  if (vertical_rules) {
193  top = prev->y + prev->h;
194  bottom = next->y;
195  left = std::min(prev->x, next->x);
196  right = std::max(prev->x + prev->w, next->x + next->w);
197  } else if (rtl_rules) {
198  // With RTL we have to account for BiDi.
199  // Right becomes the min left of all prior boxes back to the first
200  // space or newline.
201  right = prev->x;
202  left = next->x + next->w;
203  for (int j = i - 2; j >= 0 && (*boxes)[j]->ch_ != " " && (*boxes)[j]->ch_ != "\t"; --j) {
204  prev = (*boxes)[j]->box_;
205  ASSERT_HOST(prev != nullptr);
206  if (prev->x < right) {
207  right = prev->x;
208  }
209  }
210  // Left becomes the max right of all next boxes forward to the first
211  // space or newline.
212  for (size_t j = i + 2;
213  j < boxes->size() && (*boxes)[j]->box_ != nullptr && (*boxes)[j]->ch_ != "\t"; ++j) {
214  next = (*boxes)[j]->box_;
215  if (next->x + next->w > left) {
216  left = next->x + next->w;
217  }
218  }
219  }
220  // Italic and stylized characters can produce negative spaces, which
221  // Leptonica doesn't like, so clip to a positive size.
222  if (right <= left) {
223  right = left + 1;
224  }
225  if (bottom <= top) {
226  bottom = top + 1;
227  }
228  (*boxes)[i]->AddBox(left, top, right - left, bottom - top);
229  (*boxes)[i]->ch_ = " ";
230  }
231  }
232 }
233 
234 // Reorders text in a right-to-left script in left-to-right order.
235 /* static */
236 void BoxChar::ReorderRTLText(std::vector<BoxChar *> *boxes) {
237  // Ideally we need the inverse of the algorithm used by ResultIterator.
238  // For now, let's try a sort that reverses original positions for RTL
239  // characters, otherwise by x-position. This should be much closer to
240  // correct than just sorting by x-position.
241  size_t num_boxes = boxes->size();
242  for (size_t i = 0; i < num_boxes; ++i) {
243  int num_rtl = 0, num_ltr = 0;
244  (*boxes)[i]->GetDirection(&num_rtl, &num_ltr);
245  if (num_rtl > num_ltr) {
246  (*boxes)[i]->set_rtl_index(i);
247  (*boxes)[i]->ReverseUnicodesInBox();
248  }
249  }
250  BoxCharPtrSort sorter;
251  size_t end = 0;
252  for (size_t start = 0; start < boxes->size(); start = end + 1) {
253  end = start + 1;
254  while (end < boxes->size() && (*boxes)[end]->ch_ != "\t") {
255  ++end;
256  }
257  std::sort(boxes->begin() + start, boxes->begin() + end, sorter);
258  }
259 }
260 
261 // Returns true if the vector contains mostly RTL characters.
262 /* static */
263 bool BoxChar::ContainsMostlyRTL(const std::vector<BoxChar *> &boxes) {
264  int num_rtl = 0, num_ltr = 0;
265  for (auto boxe : boxes) {
266  boxe->GetDirection(&num_rtl, &num_ltr);
267  }
268  return num_rtl > num_ltr;
269 }
270 
271 // Returns true if the text is mostly laid out vertically.
272 /* static */
273 bool BoxChar::MostlyVertical(const std::vector<BoxChar *> &boxes) {
274  int64_t total_dx = 0, total_dy = 0;
275  for (size_t i = 1; i < boxes.size(); ++i) {
276  if (boxes[i - 1]->box_ != nullptr && boxes[i]->box_ != nullptr &&
277  boxes[i - 1]->page_ == boxes[i]->page_) {
278  int dx = boxes[i]->box_->x - boxes[i - 1]->box_->x;
279  int dy = boxes[i]->box_->y - boxes[i - 1]->box_->y;
280  if (abs(dx) > abs(dy) * kMinNewlineRatio || abs(dy) > abs(dx) * kMinNewlineRatio) {
281  total_dx += dx * dx;
282  total_dy += dy * dy;
283  }
284  }
285  }
286  return total_dy > total_dx;
287 }
288 
289 // Returns the total length of all the strings in the boxes.
290 /* static */
291 int BoxChar::TotalByteLength(const std::vector<BoxChar *> &boxes) {
292  int total_length = 0;
293  for (auto boxe : boxes) {
294  total_length += boxe->ch_.size();
295  }
296  return total_length;
297 }
298 
299 // Rotate the boxes in [start_box, end_box) by the given rotation.
300 // The rotation is in radians clockwise about the given center.
301 /* static */
302 void BoxChar::RotateBoxes(float rotation, int xcenter, int ycenter, int start_box, int end_box,
303  std::vector<BoxChar *> *boxes) {
304  Boxa *orig = boxaCreate(0);
305  for (int i = start_box; i < end_box; ++i) {
306  BOX *box = (*boxes)[i]->box_;
307  if (box) {
308  boxaAddBox(orig, box, L_CLONE);
309  }
310  }
311  Boxa *rotated = boxaRotate(orig, xcenter, ycenter, rotation);
312  boxaDestroy(&orig);
313  for (int i = start_box, box_ind = 0; i < end_box; ++i) {
314  if ((*boxes)[i]->box_) {
315  boxDestroy(&((*boxes)[i]->box_));
316  (*boxes)[i]->box_ = boxaGetBox(rotated, box_ind++, L_CLONE);
317  }
318  }
319  boxaDestroy(&rotated);
320 }
321 
322 const int kMaxLineLength = 1024;
323 /* static */
324 void BoxChar::WriteTesseractBoxFile(const std::string &filename, int height,
325  const std::vector<BoxChar *> &boxes) {
326  std::string output = GetTesseractBoxStr(height, boxes);
327  File::WriteStringToFileOrDie(output, filename);
328 }
329 
330 /* static */
331 std::string BoxChar::GetTesseractBoxStr(int height, const std::vector<BoxChar *> &boxes) {
332  std::string output;
333  char buffer[kMaxLineLength];
334  for (auto boxe : boxes) {
335  const Box *box = boxe->box_;
336  if (box == nullptr) {
337  tprintf("Error: Call PrepareToWrite before WriteTesseractBoxFile!!\n");
338  return "";
339  }
340  int nbytes = snprintf(buffer, kMaxLineLength, "%s %d %d %d %d %d\n", boxe->ch_.c_str(), box->x,
341  height - box->y - box->h, box->x + box->w, height - box->y, boxe->page_);
342  output.append(buffer, nbytes);
343  }
344  return output;
345 }
346 
347 } // namespace tesseract
#define ASSERT_HOST(x)
Definition: errcode.h:59
const int kMinNewlineRatio
Definition: boxchar.cpp:35
void tprintf(const char *format,...)
Definition: tprintf.cpp:41
signed int char32
Definition: unichar.h:51
const int kMaxLineLength
Definition: boxchar.cpp:322
static std::vector< char32 > UTF8ToUTF32(const char *utf8_str)
Definition: unichar.cpp:220
static std::string UTF32ToUTF8(const std::vector< char32 > &str32)
Definition: unichar.cpp:237
static bool MostlyVertical(const std::vector< BoxChar * > &boxes)
Definition: boxchar.cpp:273
static void WriteTesseractBoxFile(const std::string &name, int height, const std::vector< BoxChar * > &boxes)
Definition: boxchar.cpp:324
static void PrepareToWrite(std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:96
static void InsertSpaces(bool rtl_rules, bool vertical_rules, std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:179
BoxChar(const char *utf8_str, int len)
Definition: boxchar.cpp:39
void ReverseUnicodesInBox()
Definition: boxchar.cpp:76
void GetDirection(int *num_rtl, int *num_ltr) const
Definition: boxchar.cpp:52
static void ReorderRTLText(std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:236
const std::string & ch() const
Definition: boxchar.h:43
static int TotalByteLength(const std::vector< BoxChar * > &boxes)
Definition: boxchar.cpp:291
static std::string GetTesseractBoxStr(int height, const std::vector< BoxChar * > &boxes)
Definition: boxchar.cpp:331
static void TranslateBoxes(int xshift, int yshift, std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:83
void AddBox(int x, int y, int width, int height)
Definition: boxchar.cpp:46
static void RotateBoxes(float rotation, int xcenter, int ycenter, int start_box, int end_box, std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:302
const Box * box() const
Definition: boxchar.h:46
static bool ContainsMostlyRTL(const std::vector< BoxChar * > &boxes)
Definition: boxchar.cpp:263
static void InsertNewlines(bool rtl_rules, bool vertical_rules, std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:113
static void WriteStringToFileOrDie(const std::string &str, const std::string &filename)
Definition: fileio.cpp:54