tesseract  5.0.0
stringrenderer.cpp
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1 /**********************************************************************
2  * File: stringrenderer.cpp
3  * Description: Class for rendering UTF-8 text to an image, and retrieving
4  * bounding boxes around each grapheme cluster.
5  * Author: Ranjith Unnikrishnan
6  *
7  * (C) Copyright 2013, Google Inc.
8  * Licensed under the Apache License, Version 2.0 (the "License");
9  * you may not use this file except in compliance with the License.
10  * You may obtain a copy of the License at
11  * http://www.apache.org/licenses/LICENSE-2.0
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  *
18  **********************************************************************/
19 
20 #include "stringrenderer.h"
21 
22 #include <allheaders.h> // from leptonica
23 #include "boxchar.h"
24 #include "helpers.h" // for TRand
25 #include "ligature_table.h"
26 #include "normstrngs.h"
27 #include "tlog.h"
28 
29 #include <tesseract/unichar.h>
30 
31 #include "pango/pango-font.h"
32 #include "pango/pango-glyph-item.h"
33 #include "unicode/uchar.h" // from libicu
34 
35 #include <algorithm>
36 #include <cassert>
37 #include <cstdio>
38 #include <cstring>
39 #include <map>
40 #include <utility>
41 #include <vector>
42 
43 #define DISABLE_HEAP_LEAK_CHECK
44 
45 namespace tesseract {
46 
47 static const int kDefaultOutputResolution = 300;
48 
49 // Word joiner (U+2060) inserted after letters in ngram mode, as per
50 // recommendation in http://unicode.org/reports/tr14/ to avoid line-breaks at
51 // hyphens and other non-alpha characters.
52 static const char *kWordJoinerUTF8 = "\u2060";
53 
54 static bool IsCombiner(int ch) {
55  const int char_type = u_charType(ch);
56  return ((char_type == U_NON_SPACING_MARK) || (char_type == U_ENCLOSING_MARK) ||
57  (char_type == U_COMBINING_SPACING_MARK));
58 }
59 
60 static std::string EncodeAsUTF8(const char32 ch32) {
61  UNICHAR uni_ch(ch32);
62  return std::string(uni_ch.utf8(), uni_ch.utf8_len());
63 }
64 
65 // Returns true with probability 'prob'.
66 static bool RandBool(const double prob, TRand *rand) {
67  if (prob == 1.0) {
68  return true;
69  }
70  if (prob == 0.0) {
71  return false;
72  }
73  return rand->UnsignedRand(1.0) < prob;
74 }
75 
76 /* static */
77 static Image CairoARGB32ToPixFormat(cairo_surface_t *surface) {
78  if (cairo_image_surface_get_format(surface) != CAIRO_FORMAT_ARGB32) {
79  printf("Unexpected surface format %d\n", cairo_image_surface_get_format(surface));
80  return nullptr;
81  }
82  const int width = cairo_image_surface_get_width(surface);
83  const int height = cairo_image_surface_get_height(surface);
84  Image pix = pixCreate(width, height, 32);
85  int byte_stride = cairo_image_surface_get_stride(surface);
86 
87  for (int i = 0; i < height; ++i) {
88  memcpy(reinterpret_cast<unsigned char *>(pix->data + i * pix->wpl) + 1,
89  cairo_image_surface_get_data(surface) + i * byte_stride,
90  byte_stride - ((i == height - 1) ? 1 : 0));
91  }
92  return pix;
93 }
94 
95 StringRenderer::StringRenderer(const std::string &font_desc, int page_width, int page_height)
96  : font_(font_desc)
97  , page_width_(page_width)
98  , page_height_(page_height)
99  , h_margin_(50)
100  , v_margin_(50)
101  , pen_color_{0.0, 0.0, 0.0}
102  , char_spacing_(0)
103  , leading_(0)
104  , vertical_text_(false)
105  , gravity_hint_strong_(false)
106  , render_fullwidth_latin_(false)
107  , underline_start_prob_(0)
108  , underline_continuation_prob_(0)
109  , underline_style_(PANGO_UNDERLINE_SINGLE)
110  , drop_uncovered_chars_(true)
111  , strip_unrenderable_words_(false)
112  , add_ligatures_(false)
113  , output_word_boxes_(false)
114  , surface_(nullptr)
115  , cr_(nullptr)
116  , layout_(nullptr)
117  , start_box_(0)
118  , page_(0)
119  , box_padding_(0)
120  , page_boxes_(nullptr)
121  , total_chars_(0)
122  , font_index_(0)
123  , last_offset_(0) {
124  set_resolution(kDefaultOutputResolution);
125  set_font(font_desc);
126 }
127 
128 bool StringRenderer::set_font(const std::string &desc) {
129  bool success = font_.ParseFontDescriptionName(desc);
131  return success;
132 }
133 
134 void StringRenderer::set_resolution(const int resolution) {
135  resolution_ = resolution;
136  font_.set_resolution(resolution);
137 }
138 
140  underline_start_prob_ = std::min(std::max(frac, 0.0), 1.0);
141 }
142 
144  underline_continuation_prob_ = std::min(std::max(frac, 0.0), 1.0);
145 }
146 
148  ClearBoxes();
149  FreePangoCairo();
150 }
151 
153  FreePangoCairo();
154  surface_ = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, page_width_, page_height_);
155  cr_ = cairo_create(surface_);
156  {
158  layout_ = pango_cairo_create_layout(cr_);
159  }
160 
161  if (vertical_text_) {
162  PangoContext *context = pango_layout_get_context(layout_);
163  pango_context_set_base_gravity(context, PANGO_GRAVITY_EAST);
164  if (gravity_hint_strong_) {
165  pango_context_set_gravity_hint(context, PANGO_GRAVITY_HINT_STRONG);
166  }
167  pango_layout_context_changed(layout_);
168  }
169 
171 }
172 
174  std::string font_desc = font_.DescriptionName();
175  // Specify the font via a description name
176  PangoFontDescription *desc = pango_font_description_from_string(font_desc.c_str());
177  // Assign the font description to the layout
178  pango_layout_set_font_description(layout_, desc);
179  pango_font_description_free(desc); // free the description
180  pango_cairo_context_set_resolution(pango_layout_get_context(layout_), resolution_);
181 
182  int max_width = page_width_ - 2 * h_margin_;
183  int max_height = page_height_ - 2 * v_margin_;
184  tlog(3, "max_width = %d, max_height = %d\n", max_width, max_height);
185  if (vertical_text_) {
186  using std::swap;
187  swap(max_width, max_height);
188  }
189  pango_layout_set_width(layout_, max_width * PANGO_SCALE);
190  // Ultra-wide Thai strings need to wrap at char level.
191  pango_layout_set_wrap(layout_, PANGO_WRAP_WORD_CHAR);
192 
193  // Adjust character spacing
194  PangoAttrList *attr_list = pango_attr_list_new();
195  if (char_spacing_) {
196  PangoAttribute *spacing_attr = pango_attr_letter_spacing_new(char_spacing_ * PANGO_SCALE);
197  spacing_attr->start_index = 0;
198  spacing_attr->end_index = static_cast<guint>(-1);
199  pango_attr_list_change(attr_list, spacing_attr);
200  }
201 
202  if (add_ligatures_) {
203  set_features("liga, clig, dlig, hlig");
204  PangoAttribute *feature_attr = pango_attr_font_features_new(features_.c_str());
205  pango_attr_list_change(attr_list, feature_attr);
206  }
207 
208  pango_layout_set_attributes(layout_, attr_list);
209  pango_attr_list_unref(attr_list);
210  // Adjust line spacing
211  if (leading_) {
212  pango_layout_set_spacing(layout_, leading_ * PANGO_SCALE);
213  }
214 }
215 
217  if (layout_) {
218  g_object_unref(layout_);
219  layout_ = nullptr;
220  }
221  if (cr_) {
222  cairo_destroy(cr_);
223  cr_ = nullptr;
224  }
225  if (surface_) {
226  cairo_surface_destroy(surface_);
227  surface_ = nullptr;
228  }
229 }
230 
231 void StringRenderer::SetWordUnderlineAttributes(const std::string &page_text) {
232  if (underline_start_prob_ == 0) {
233  return;
234  }
235  PangoAttrList *attr_list = pango_layout_get_attributes(layout_);
236 
237  const char *text = page_text.c_str();
238  size_t offset = 0;
239  TRand rand;
240  bool started_underline = false;
241  PangoAttribute *und_attr = nullptr;
242 
243  while (offset < page_text.length()) {
244  offset += SpanUTF8Whitespace(text + offset);
245  if (offset == page_text.length()) {
246  break;
247  }
248 
249  int word_start = offset;
250  int word_len = SpanUTF8NotWhitespace(text + offset);
251  offset += word_len;
252  if (started_underline) {
253  // Should we continue the underline to the next word?
254  if (RandBool(underline_continuation_prob_, &rand)) {
255  // Continue the current underline to this word.
256  und_attr->end_index = word_start + word_len;
257  } else {
258  // Otherwise end the current underline attribute at the end of the
259  // previous word.
260  pango_attr_list_insert(attr_list, und_attr);
261  started_underline = false;
262  und_attr = nullptr;
263  }
264  }
265  if (!started_underline && RandBool(underline_start_prob_, &rand)) {
266  // Start a new underline attribute
267  und_attr = pango_attr_underline_new(underline_style_);
268  und_attr->start_index = word_start;
269  und_attr->end_index = word_start + word_len;
270  started_underline = true;
271  }
272  }
273  // Finish the current underline attribute at the end of the page.
274  if (started_underline) {
275  und_attr->end_index = page_text.length();
276  pango_attr_list_insert(attr_list, und_attr);
277  }
278 }
279 
280 // Returns offset in utf8 bytes to first page.
281 int StringRenderer::FindFirstPageBreakOffset(const char *text, int text_length) {
282  if (!text_length) {
283  return 0;
284  }
285  const int max_height = (page_height_ - 2 * v_margin_);
286  const int max_width = (page_width_ - 2 * h_margin_);
287  const int max_layout_height = vertical_text_ ? max_width : max_height;
288 
289  UNICHAR::const_iterator it = UNICHAR::begin(text, text_length);
290  const UNICHAR::const_iterator it_end = UNICHAR::end(text, text_length);
291  const int kMaxUnicodeBufLength = 15000;
292  for (int i = 0; i < kMaxUnicodeBufLength && it != it_end; ++it, ++i) {
293  ;
294  }
295  int buf_length = it.utf8_data() - text;
296  tlog(1, "len = %d buf_len = %d\n", text_length, buf_length);
297  pango_layout_set_text(layout_, text, buf_length);
298 
299  PangoLayoutIter *line_iter = nullptr;
300  { // Fontconfig caches some info here that is not freed before exit.
302  line_iter = pango_layout_get_iter(layout_);
303  }
304  bool first_page = true;
305  int page_top = 0;
306  int offset = buf_length;
307  do {
308  // Get bounding box of the current line
309  PangoRectangle line_ink_rect;
310  pango_layout_iter_get_line_extents(line_iter, &line_ink_rect, nullptr);
311  pango_extents_to_pixels(&line_ink_rect, nullptr);
312  PangoLayoutLine *line = pango_layout_iter_get_line_readonly(line_iter);
313  if (first_page) {
314  page_top = line_ink_rect.y;
315  first_page = false;
316  }
317  int line_bottom = line_ink_rect.y + line_ink_rect.height;
318  if (line_bottom - page_top > max_layout_height) {
319  offset = line->start_index;
320  tlog(1, "Found offset = %d\n", offset);
321  break;
322  }
323  } while (pango_layout_iter_next_line(line_iter));
324  pango_layout_iter_free(line_iter);
325  return offset;
326 }
327 
328 const std::vector<BoxChar *> &StringRenderer::GetBoxes() const {
329  return boxchars_;
330 }
331 
333  return page_boxes_;
334 }
335 
336 void StringRenderer::RotatePageBoxes(float rotation) {
338  &boxchars_);
339 }
340 
342  for (auto &boxchar : boxchars_) {
343  delete boxchar;
344  }
345  boxchars_.clear();
346  boxaDestroy(&page_boxes_);
347 }
348 
352 }
353 
354 void StringRenderer::WriteAllBoxes(const std::string &filename) {
357 }
358 
359 // Returns cluster strings in logical order.
360 bool StringRenderer::GetClusterStrings(std::vector<std::string> *cluster_text) {
361  std::map<int, std::string> start_byte_to_text;
362  PangoLayoutIter *run_iter = pango_layout_get_iter(layout_);
363  const char *full_text = pango_layout_get_text(layout_);
364  do {
365  PangoLayoutRun *run = pango_layout_iter_get_run_readonly(run_iter);
366  if (!run) {
367  // End of line nullptr run marker
368  tlog(2, "Found end of line marker\n");
369  continue;
370  }
371  PangoGlyphItemIter cluster_iter;
372  gboolean have_cluster;
373  for (have_cluster = pango_glyph_item_iter_init_start(&cluster_iter, run, full_text);
374  have_cluster; have_cluster = pango_glyph_item_iter_next_cluster(&cluster_iter)) {
375  const int start_byte_index = cluster_iter.start_index;
376  const int end_byte_index = cluster_iter.end_index;
377  std::string text =
378  std::string(full_text + start_byte_index, end_byte_index - start_byte_index);
379  if (IsUTF8Whitespace(text.c_str())) {
380  tlog(2, "Found whitespace\n");
381  text = " ";
382  }
383  tlog(2, "start_byte=%d end_byte=%d : '%s'\n", start_byte_index, end_byte_index, text.c_str());
384  if (add_ligatures_) {
385  // Make sure the output box files have ligatured text in case the font
386  // decided to use an unmapped glyph.
387  text = LigatureTable::Get()->AddLigatures(text, nullptr);
388  }
389  start_byte_to_text[start_byte_index] = text;
390  }
391  } while (pango_layout_iter_next_run(run_iter));
392  pango_layout_iter_free(run_iter);
393 
394  cluster_text->clear();
395  for (auto it = start_byte_to_text.begin(); it != start_byte_to_text.end(); ++it) {
396  cluster_text->push_back(it->second);
397  }
398  return !cluster_text->empty();
399 }
400 
401 // Merges an array of BoxChars into words based on the identification of
402 // BoxChars containing the space character as inter-word separators.
403 //
404 // Sometime two adjacent characters in the sequence may be detected as lying on
405 // different lines based on their spatial positions. This may be the result of a
406 // newline character at end of the last word on a line in the source text, or of
407 // a discretionary line-break created by Pango at intra-word locations like
408 // hyphens. When this is detected the word is split at that location into
409 // multiple BoxChars. Otherwise, each resulting BoxChar will contain a word and
410 // its bounding box.
411 static void MergeBoxCharsToWords(std::vector<BoxChar *> *boxchars) {
412  std::vector<BoxChar *> result;
413  bool started_word = false;
414  for (auto &boxchar : *boxchars) {
415  if (boxchar->ch() == " " || boxchar->box() == nullptr) {
416  result.push_back(boxchar);
417  boxchar = nullptr;
418  started_word = false;
419  continue;
420  }
421 
422  if (!started_word) {
423  // Begin new word
424  started_word = true;
425  result.push_back(boxchar);
426  boxchar = nullptr;
427  } else {
428  BoxChar *last_boxchar = result.back();
429  // Compute bounding box union
430  const Box *box = boxchar->box();
431  Box *last_box = last_boxchar->mutable_box();
432  int left = std::min(last_box->x, box->x);
433  int right = std::max(last_box->x + last_box->w, box->x + box->w);
434  int top = std::min(last_box->y, box->y);
435  int bottom = std::max(last_box->y + last_box->h, box->y + box->h);
436  // Conclude that the word was broken to span multiple lines based on the
437  // size of the merged bounding box in relation to those of the individual
438  // characters seen so far.
439  if (right - left > last_box->w + 5 * box->w) {
440  tlog(1, "Found line break after '%s'", last_boxchar->ch().c_str());
441  // Insert a fake interword space and start a new word with the current
442  // boxchar.
443  result.push_back(new BoxChar(" ", 1));
444  result.push_back(boxchar);
445  boxchar = nullptr;
446  continue;
447  }
448  // Append to last word
449  last_boxchar->mutable_ch()->append(boxchar->ch());
450  last_box->x = left;
451  last_box->w = right - left;
452  last_box->y = top;
453  last_box->h = bottom - top;
454  delete boxchar;
455  boxchar = nullptr;
456  }
457  }
458  boxchars->swap(result);
459 }
460 
462  const char *text = pango_layout_get_text(layout_);
463  PangoLayoutIter *cluster_iter = pango_layout_get_iter(layout_);
464 
465  // Do a first pass to store cluster start indexes.
466  std::vector<int> cluster_start_indices;
467  do {
468  cluster_start_indices.push_back(pango_layout_iter_get_index(cluster_iter));
469  tlog(3, "Added %d\n", cluster_start_indices.back());
470  } while (pango_layout_iter_next_cluster(cluster_iter));
471  pango_layout_iter_free(cluster_iter);
472  cluster_start_indices.push_back(strlen(text));
473  tlog(3, "Added last index %d\n", cluster_start_indices.back());
474  // Sort the indices and create a map from start to end indices.
475  std::sort(cluster_start_indices.begin(), cluster_start_indices.end());
476  std::map<int, int> cluster_start_to_end_index;
477  for (size_t i = 0; i + 1 < cluster_start_indices.size(); ++i) {
478  cluster_start_to_end_index[cluster_start_indices[i]] = cluster_start_indices[i + 1];
479  }
480 
481  // Iterate again to compute cluster boxes and their text with the obtained
482  // cluster extent information.
483  cluster_iter = pango_layout_get_iter(layout_);
484  // Store BoxChars* sorted by their byte start positions
485  std::map<int, BoxChar *> start_byte_to_box;
486  do {
487  PangoRectangle cluster_rect;
488  pango_layout_iter_get_cluster_extents(cluster_iter, &cluster_rect, nullptr);
489  pango_extents_to_pixels(&cluster_rect, nullptr);
490  const int start_byte_index = pango_layout_iter_get_index(cluster_iter);
491  const int end_byte_index = cluster_start_to_end_index[start_byte_index];
492  std::string cluster_text =
493  std::string(text + start_byte_index, end_byte_index - start_byte_index);
494  if (!cluster_text.empty() && cluster_text[0] == '\n') {
495  tlog(2, "Skipping newlines at start of text.\n");
496  continue;
497  }
498  if (!cluster_rect.width || !cluster_rect.height || IsUTF8Whitespace(cluster_text.c_str())) {
499  tlog(2, "Skipping whitespace with boxdim (%d,%d) '%s'\n", cluster_rect.width,
500  cluster_rect.height, cluster_text.c_str());
501  auto *boxchar = new BoxChar(" ", 1);
502  boxchar->set_page(page_);
503  start_byte_to_box[start_byte_index] = boxchar;
504  continue;
505  }
506  // Prepare a boxchar for addition at this byte position.
507  tlog(2, "[%d %d], %d, %d : start_byte=%d end_byte=%d : '%s'\n", cluster_rect.x, cluster_rect.y,
508  cluster_rect.width, cluster_rect.height, start_byte_index, end_byte_index,
509  cluster_text.c_str());
510  ASSERT_HOST_MSG(cluster_rect.width, "cluster_text:%s start_byte_index:%d\n",
511  cluster_text.c_str(), start_byte_index);
512  ASSERT_HOST_MSG(cluster_rect.height, "cluster_text:%s start_byte_index:%d\n",
513  cluster_text.c_str(), start_byte_index);
514  if (box_padding_) {
515  cluster_rect.x = std::max(0, cluster_rect.x - box_padding_);
516  cluster_rect.width += 2 * box_padding_;
517  cluster_rect.y = std::max(0, cluster_rect.y - box_padding_);
518  cluster_rect.height += 2 * box_padding_;
519  }
520  if (add_ligatures_) {
521  // Make sure the output box files have ligatured text in case the font
522  // decided to use an unmapped glyph.
523  cluster_text = LigatureTable::Get()->AddLigatures(cluster_text, nullptr);
524  }
525  auto *boxchar = new BoxChar(cluster_text.c_str(), cluster_text.size());
526  boxchar->set_page(page_);
527  boxchar->AddBox(cluster_rect.x, cluster_rect.y, cluster_rect.width, cluster_rect.height);
528  start_byte_to_box[start_byte_index] = boxchar;
529  } while (pango_layout_iter_next_cluster(cluster_iter));
530  pango_layout_iter_free(cluster_iter);
531 
532  // There is a subtle bug in the cluster text reported by the PangoLayoutIter
533  // on ligatured characters (eg. The word "Lam-Aliph" in arabic). To work
534  // around this, we use text reported using the PangoGlyphIter which is
535  // accurate.
536  // TODO(ranjith): Revisit whether this is still needed in newer versions of
537  // pango.
538  std::vector<std::string> cluster_text;
539  if (GetClusterStrings(&cluster_text)) {
540  ASSERT_HOST(cluster_text.size() == start_byte_to_box.size());
541  int ind = 0;
542  for (auto it = start_byte_to_box.begin(); it != start_byte_to_box.end(); ++it, ++ind) {
543  it->second->mutable_ch()->swap(cluster_text[ind]);
544  }
545  }
546 
547  // Append to the boxchars list in byte order.
548  std::vector<BoxChar *> page_boxchars;
549  page_boxchars.reserve(start_byte_to_box.size());
550  std::string last_ch;
551  for (auto it = start_byte_to_box.begin(); it != start_byte_to_box.end(); ++it) {
552  if (it->second->ch() == kWordJoinerUTF8) {
553  // Skip zero-width joiner characters (ZWJs) here.
554  delete it->second;
555  } else {
556  page_boxchars.push_back(it->second);
557  }
558  }
559  CorrectBoxPositionsToLayout(&page_boxchars);
560 
562  for (auto &it : start_byte_to_box) {
563  // Convert fullwidth Latin characters to their halfwidth forms.
564  std::string half(ConvertFullwidthLatinToBasicLatin(it.second->ch()));
565  it.second->mutable_ch()->swap(half);
566  }
567  }
568 
569  // Merge the character boxes into word boxes if we are rendering n-grams.
570  if (output_word_boxes_) {
571  MergeBoxCharsToWords(&page_boxchars);
572  }
573 
574  boxchars_.insert(boxchars_.end(), page_boxchars.begin(), page_boxchars.end());
575 
576  // Compute the page bounding box
577  Box *page_box = nullptr;
578  Boxa *all_boxes = nullptr;
579  for (auto &page_boxchar : page_boxchars) {
580  if (page_boxchar->box() == nullptr) {
581  continue;
582  }
583  if (all_boxes == nullptr) {
584  all_boxes = boxaCreate(0);
585  }
586  boxaAddBox(all_boxes, page_boxchar->mutable_box(), L_CLONE);
587  }
588  if (all_boxes != nullptr) {
589  boxaGetExtent(all_boxes, nullptr, nullptr, &page_box);
590  boxaDestroy(&all_boxes);
591  if (page_boxes_ == nullptr) {
592  page_boxes_ = boxaCreate(0);
593  }
594  boxaAddBox(page_boxes_, page_box, L_INSERT);
595  }
596 }
597 
598 void StringRenderer::CorrectBoxPositionsToLayout(std::vector<BoxChar *> *boxchars) {
599  if (vertical_text_) {
600  const double rotation = -pango_gravity_to_rotation(
601  pango_context_get_base_gravity(pango_layout_get_context(layout_)));
603  BoxChar::RotateBoxes(rotation, page_width_ - h_margin_, v_margin_, 0, boxchars->size(),
604  boxchars);
605  } else {
607  }
608 }
609 
610 int StringRenderer::StripUnrenderableWords(std::string *utf8_text) const {
611  std::string output_text;
612  const char *text = utf8_text->c_str();
613  size_t offset = 0;
614  int num_dropped = 0;
615  while (offset < utf8_text->length()) {
616  int space_len = SpanUTF8Whitespace(text + offset);
617  output_text.append(text + offset, space_len);
618  offset += space_len;
619  if (offset == utf8_text->length()) {
620  break;
621  }
622 
623  int word_len = SpanUTF8NotWhitespace(text + offset);
624  if (font_.CanRenderString(text + offset, word_len)) {
625  output_text.append(text + offset, word_len);
626  } else {
627  ++num_dropped;
628  }
629  offset += word_len;
630  }
631  utf8_text->swap(output_text);
632 
633  if (num_dropped > 0) {
634  tprintf("Stripped %d unrenderable words\n", num_dropped);
635  }
636  return num_dropped;
637 }
638 
639 int StringRenderer::RenderToGrayscaleImage(const char *text, int text_length, Image *pix) {
640  Image orig_pix = nullptr;
641  int offset = RenderToImage(text, text_length, &orig_pix);
642  if (orig_pix) {
643  *pix = pixConvertTo8(orig_pix, false);
644  orig_pix.destroy();
645  }
646  return offset;
647 }
648 
649 int StringRenderer::RenderToBinaryImage(const char *text, int text_length, int threshold,
650  Image *pix) {
651  Image orig_pix = nullptr;
652  int offset = RenderToImage(text, text_length, &orig_pix);
653  if (orig_pix) {
654  Image gray_pix = pixConvertTo8(orig_pix, false);
655  orig_pix.destroy();
656  *pix = pixThresholdToBinary(gray_pix, threshold);
657  gray_pix.destroy();
658  } else {
659  *pix = orig_pix;
660  }
661  return offset;
662 }
663 
664 // Add word joiner (WJ) characters between adjacent non-space characters except
665 // immediately before a combiner.
666 /* static */
667 std::string StringRenderer::InsertWordJoiners(const std::string &text) {
668  std::string out_str;
669  const UNICHAR::const_iterator it_end = UNICHAR::end(text.c_str(), text.length());
670  for (UNICHAR::const_iterator it = UNICHAR::begin(text.c_str(), text.length()); it != it_end;
671  ++it) {
672  // Add the symbol to the output string.
673  out_str.append(it.utf8_data(), it.utf8_len());
674  // Check the next symbol.
675  UNICHAR::const_iterator next_it = it;
676  ++next_it;
677  bool next_char_is_boundary = (next_it == it_end || *next_it == ' ');
678  bool next_char_is_combiner = (next_it == it_end) ? false : IsCombiner(*next_it);
679  if (*it != ' ' && *it != '\n' && !next_char_is_boundary && !next_char_is_combiner) {
680  out_str += kWordJoinerUTF8;
681  }
682  }
683  return out_str;
684 }
685 
686 // Convert halfwidth Basic Latin characters to their fullwidth forms.
687 std::string StringRenderer::ConvertBasicLatinToFullwidthLatin(const std::string &str) {
688  std::string full_str;
689  const UNICHAR::const_iterator it_end = UNICHAR::end(str.c_str(), str.length());
690  for (UNICHAR::const_iterator it = UNICHAR::begin(str.c_str(), str.length()); it != it_end; ++it) {
691  // Convert printable and non-space 7-bit ASCII characters to
692  // their fullwidth forms.
693  if (IsInterchangeValid7BitAscii(*it) && isprint(*it) && !isspace(*it)) {
694  // Convert by adding 0xFEE0 to the codepoint of 7-bit ASCII.
695  char32 full_char = *it + 0xFEE0;
696  full_str.append(EncodeAsUTF8(full_char));
697  } else {
698  full_str.append(it.utf8_data(), it.utf8_len());
699  }
700  }
701  return full_str;
702 }
703 
704 // Convert fullwidth Latin characters to their halfwidth forms.
705 std::string StringRenderer::ConvertFullwidthLatinToBasicLatin(const std::string &str) {
706  std::string half_str;
707  UNICHAR::const_iterator it_end = UNICHAR::end(str.c_str(), str.length());
708  for (UNICHAR::const_iterator it = UNICHAR::begin(str.c_str(), str.length()); it != it_end; ++it) {
709  char32 half_char = FullwidthToHalfwidth(*it);
710  // Convert fullwidth Latin characters to their halfwidth forms
711  // only if halfwidth forms are printable and non-space 7-bit ASCII.
712  if (IsInterchangeValid7BitAscii(half_char) && isprint(half_char) && !isspace(half_char)) {
713  half_str.append(EncodeAsUTF8(half_char));
714  } else {
715  half_str.append(it.utf8_data(), it.utf8_len());
716  }
717  }
718  return half_str;
719 }
720 
721 // Returns offset to end of text substring rendered in this method.
722 int StringRenderer::RenderToImage(const char *text, int text_length, Image *pix) {
723  if (pix && *pix) {
724  pix->destroy();
725  }
726  InitPangoCairo();
727 
728  const int page_offset = FindFirstPageBreakOffset(text, text_length);
729  if (!page_offset) {
730  return 0;
731  }
732  start_box_ = boxchars_.size();
733 
734  if (!vertical_text_) {
735  // Translate by the specified margin
736  cairo_translate(cr_, h_margin_, v_margin_);
737  } else {
738  // Vertical text rendering is achieved by a two-step process of first
739  // performing regular horizontal layout with character orientation set to
740  // EAST, and then translating and rotating the layout before rendering onto
741  // the desired image surface. The settings required for the former step are
742  // done within InitPangoCairo().
743  //
744  // Translate to the top-right margin of page
745  cairo_translate(cr_, page_width_ - h_margin_, v_margin_);
746  // Rotate the layout
747  double rotation = -pango_gravity_to_rotation(
748  pango_context_get_base_gravity(pango_layout_get_context(layout_)));
749  tlog(2, "Rotating by %f radians\n", rotation);
750  cairo_rotate(cr_, rotation);
751  pango_cairo_update_layout(cr_, layout_);
752  }
753  std::string page_text(text, page_offset);
755  // Convert Basic Latin to their fullwidth forms.
756  page_text = ConvertBasicLatinToFullwidthLatin(page_text);
757  }
759  StripUnrenderableWords(&page_text);
760  }
761  if (drop_uncovered_chars_ && !font_.CoversUTF8Text(page_text.c_str(), page_text.length())) {
762  int num_dropped = font_.DropUncoveredChars(&page_text);
763  if (num_dropped) {
764  tprintf("WARNING: Dropped %d uncovered characters\n", num_dropped);
765  }
766  }
767  if (add_ligatures_) {
768  // Add ligatures wherever possible, including custom ligatures.
769  page_text = LigatureTable::Get()->AddLigatures(page_text, &font_);
770  }
771  if (underline_start_prob_ > 0) {
772  SetWordUnderlineAttributes(page_text);
773  }
774 
775  pango_layout_set_text(layout_, page_text.c_str(), page_text.length());
776 
777  if (pix) {
778  // Set a white background for the target image surface.
779  cairo_set_source_rgb(cr_, 1.0, 1.0, 1.0); // sets drawing colour to white
780  // Fill the surface with the active colour (if you don't do this, you will
781  // be given a surface with a transparent background to draw on)
782  cairo_paint(cr_);
783  // Set the ink color to black
784  cairo_set_source_rgb(cr_, pen_color_[0], pen_color_[1], pen_color_[2]);
785  // If the target surface or transformation properties of the cairo instance
786  // have changed, update the pango layout to reflect this
787  pango_cairo_update_layout(cr_, layout_);
788  {
789  DISABLE_HEAP_LEAK_CHECK; // for Fontconfig
790  // Draw the pango layout onto the cairo surface
791  pango_cairo_show_layout(cr_, layout_);
792  }
793  *pix = CairoARGB32ToPixFormat(surface_);
794  }
796  FreePangoCairo();
797  // Update internal state variables.
798  ++page_;
799  return page_offset;
800 }
801 
802 // Render a string to an image, returning it as an 8 bit pix. Behaves as
803 // RenderString, except that it ignores the font set at construction and works
804 // through all the fonts, returning 0 until they are exhausted, at which point
805 // it returns the value it should have returned all along, but no pix this time.
806 // Fonts that don't contain a given proportion of the characters in the string
807 // get skipped.
808 // Fonts that work each get rendered and the font name gets added
809 // to the image.
810 // NOTE that no boxes are produced by this function.
811 //
812 // Example usage: To render a null terminated char-array "txt"
813 //
814 // int offset = 0;
815 // do {
816 // Image pix;
817 // offset += renderer.RenderAllFontsToImage(min_proportion, txt + offset,
818 // strlen(txt + offset), nullptr,
819 // &pix);
820 // ...
821 // } while (offset < strlen(text));
822 //
823 int StringRenderer::RenderAllFontsToImage(double min_coverage, const char *text, int text_length,
824  std::string *font_used, Image *image) {
825  *image = nullptr;
826  // Select a suitable font to render the title with.
827  const char kTitleTemplate[] = "%s : %d hits = %.2f%%, raw = %d = %.2f%%";
828  std::string title_font;
829  if (!FontUtils::SelectFont(kTitleTemplate, strlen(kTitleTemplate), &title_font, nullptr)) {
830  tprintf("WARNING: Could not find a font to render image title with!\n");
831  title_font = "Arial";
832  }
833  title_font += " 8";
834  tlog(1, "Selected title font: %s\n", title_font.c_str());
835  if (font_used) {
836  font_used->clear();
837  }
838 
839  std::string orig_font = font_.DescriptionName();
840  if (char_map_.empty()) {
841  total_chars_ = 0;
842  // Fill the hash table and use that for computing which fonts to use.
843  for (UNICHAR::const_iterator it = UNICHAR::begin(text, text_length);
844  it != UNICHAR::end(text, text_length); ++it) {
845  ++total_chars_;
846  ++char_map_[*it];
847  }
848  tprintf("Total chars = %d\n", total_chars_);
849  }
850  const std::vector<std::string> &all_fonts = FontUtils::ListAvailableFonts();
851 
852  for (size_t i = font_index_; i < all_fonts.size(); ++i) {
853  ++font_index_;
854  int raw_score = 0;
855  int ok_chars = FontUtils::FontScore(char_map_, all_fonts[i], &raw_score, nullptr);
856  if (ok_chars > 0 && ok_chars >= total_chars_ * min_coverage) {
857  set_font(all_fonts[i]);
858  int offset = RenderToBinaryImage(text, text_length, 128, image);
859  ClearBoxes(); // Get rid of them as they are garbage.
860  const int kMaxTitleLength = 1024;
861  char title[kMaxTitleLength];
862  snprintf(title, kMaxTitleLength, kTitleTemplate, all_fonts[i].c_str(), ok_chars,
863  100.0 * ok_chars / total_chars_, raw_score, 100.0 * raw_score / char_map_.size());
864  tprintf("%s\n", title);
865  // This is a good font! Store the offset to return once we've tried all
866  // the fonts.
867  if (offset) {
868  last_offset_ = offset;
869  if (font_used) {
870  *font_used = all_fonts[i];
871  }
872  }
873  // Add the font to the image.
874  set_font(title_font);
875  v_margin_ /= 8;
876  Image title_image = nullptr;
877  RenderToBinaryImage(title, strlen(title), 128, &title_image);
878  *image |= title_image;
879  title_image.destroy();
880 
881  v_margin_ *= 8;
882  set_font(orig_font);
883  // We return the real offset only after cycling through the list of fonts.
884  return 0;
885  } else {
886  tprintf("Font %s failed with %d hits = %.2f%%\n", all_fonts[i].c_str(), ok_chars,
887  100.0 * ok_chars / total_chars_);
888  }
889  }
890  font_index_ = 0;
891  char_map_.clear();
892  return last_offset_ == 0 ? -1 : last_offset_;
893 }
894 
895 } // namespace tesseract
#define ASSERT_HOST(x)
Definition: errcode.h:59
#define ASSERT_HOST_MSG(x,...)
Definition: errcode.h:62
signed int char32
#define DISABLE_HEAP_LEAK_CHECK
#define tlog(level,...)
Definition: tlog.h:36
unsigned int SpanUTF8Whitespace(const char *text)
Definition: normstrngs.cpp:237
void tprintf(const char *format,...)
Definition: tprintf.cpp:41
signed int char32
Definition: unichar.h:51
bool IsInterchangeValid7BitAscii(const char32 ch)
Definition: normstrngs.cpp:276
char32 FullwidthToHalfwidth(const char32 ch)
Definition: normstrngs.cpp:282
unsigned int SpanUTF8NotWhitespace(const char *text)
Definition: normstrngs.cpp:249
bool IsUTF8Whitespace(const char *text)
Definition: normstrngs.cpp:233
static const_iterator begin(const char *utf8_str, int byte_length)
Definition: unichar.cpp:209
static const_iterator end(const char *utf8_str, int byte_length)
Definition: unichar.cpp:213
const char * utf8_data() const
Definition: unichar.h:135
void destroy()
Definition: image.cpp:32
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 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
static void RotateBoxes(float rotation, int xcenter, int ycenter, int start_box, int end_box, std::vector< BoxChar * > *boxes)
Definition: boxchar.cpp:302
std::string AddLigatures(const std::string &str, const PangoFontInfo *font) const
static LigatureTable * Get()
void set_resolution(const int resolution)
int DropUncoveredChars(std::string *utf8_text) const
bool CoversUTF8Text(const char *utf8_text, int byte_length) const
bool ParseFontDescriptionName(const std::string &name)
std::string DescriptionName() const
bool CanRenderString(const char *utf8_word, int len, std::vector< std::string > *graphemes) const
static int FontScore(const std::unordered_map< char32, int64_t > &ch_map, const std::string &fontname, int *raw_score, std::vector< bool > *ch_flags)
static bool SelectFont(const char *utf8_word, const int utf8_len, std::string *font_name, std::vector< std::string > *graphemes)
static const std::vector< std::string > & ListAvailableFonts()
static std::string InsertWordJoiners(const std::string &text)
void SetWordUnderlineAttributes(const std::string &page_text)
bool GetClusterStrings(std::vector< std::string > *cluster_text)
void set_features(const char *features)
bool set_font(const std::string &desc)
int RenderToImage(const char *text, int text_length, Image *pix)
void set_underline_start_prob(const double frac)
static std::string ConvertBasicLatinToFullwidthLatin(const std::string &text)
int StripUnrenderableWords(std::string *utf8_text) const
int RenderAllFontsToImage(double min_coverage, const char *text, int text_length, std::string *font_used, Image *pix)
int RenderToBinaryImage(const char *text, int text_length, int threshold, Image *pix)
static std::string ConvertFullwidthLatinToBasicLatin(const std::string &text)
StringRenderer(const std::string &font_desc, int page_width, int page_height)
int FindFirstPageBreakOffset(const char *text, int text_length)
void CorrectBoxPositionsToLayout(std::vector< BoxChar * > *boxchars)
const std::vector< BoxChar * > & GetBoxes() const
void set_resolution(const int resolution)
void set_underline_continuation_prob(const double frac)
int RenderToGrayscaleImage(const char *text, int text_length, Image *pix)
cairo_surface_t * surface_
std::vector< BoxChar * > boxchars_
void WriteAllBoxes(const std::string &filename)
void RotatePageBoxes(float rotation)
std::unordered_map< char32, int64_t > char_map_
PangoUnderline underline_style_