tesseract  5.0.0
stringrenderer.h
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1 /**********************************************************************
2  * File: stringrenderer.h
3  * Description: Class for rendering UTF-8 text to an image, and retrieving
4  * bounding boxes around each grapheme cluster.
5  *
6  * Instances are created using a font description string
7  * (eg. "Arial Italic 12"; see pango_font_info.h for the format)
8  * and the page dimensions. Other renderer properties such as
9  * spacing, ligaturization, as well a preprocessing behavior such
10  * as removal of unrenderable words and a special n-gram mode may
11  * be set using respective set_* methods.
12  *
13  * Author: Ranjith Unnikrishnan
14  *
15  * (C) Copyright 2013, Google Inc.
16  * Licensed under the Apache License, Version 2.0 (the "License");
17  * you may not use this file except in compliance with the License.
18  * You may obtain a copy of the License at
19  * http://www.apache.org/licenses/LICENSE-2.0
20  * Unless required by applicable law or agreed to in writing, software
21  * distributed under the License is distributed on an "AS IS" BASIS,
22  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
23  * See the License for the specific language governing permissions and
24  * limitations under the License.
25  *
26  **********************************************************************/
27 
28 #ifndef TESSERACT_TRAINING_STRINGRENDERER_H_
29 #define TESSERACT_TRAINING_STRINGRENDERER_H_
30 
31 #include "export.h"
32 
33 #include "pango/pango-layout.h"
34 #include "pango/pangocairo.h"
35 #include "pango_font_info.h"
36 
37 #include "image.h"
38 
39 #include <string>
40 #include <unordered_map>
41 #include <vector>
42 
43 struct Boxa;
44 struct Pix;
45 
46 namespace tesseract {
47 
48 class BoxChar;
49 
50 class TESS_PANGO_TRAINING_API StringRenderer {
51 public:
52  StringRenderer(const std::string &font_desc, int page_width, int page_height);
53  ~StringRenderer();
54 
55  // Renders the text with the chosen font and returns the byte offset up to
56  // which the text could be rendered so as to fit the specified page
57  // dimensions.
58  int RenderToImage(const char *text, int text_length, Image *pix);
59  int RenderToGrayscaleImage(const char *text, int text_length, Image *pix);
60  int RenderToBinaryImage(const char *text, int text_length, int threshold, Image *pix);
61  // Renders a line of text with all available fonts that were able to render
62  // at least min_coverage fraction of the input text. Use 1.0 to require that
63  // a font be able to render all the text.
64  int RenderAllFontsToImage(double min_coverage, const char *text, int text_length,
65  std::string *font_used, Image *pix);
66 
67  bool set_font(const std::string &desc);
68  // Char spacing is in PIXELS!!!!.
69  void set_char_spacing(int char_spacing) {
70  char_spacing_ = char_spacing;
71  }
72  void set_leading(int leading) {
73  leading_ = leading;
74  }
75  void set_resolution(const int resolution);
76  void set_vertical_text(bool vertical_text) {
77  vertical_text_ = vertical_text;
78  }
79  void set_gravity_hint_strong(bool gravity_hint_strong) {
80  gravity_hint_strong_ = gravity_hint_strong;
81  }
82  void set_render_fullwidth_latin(bool render_fullwidth_latin) {
83  render_fullwidth_latin_ = render_fullwidth_latin;
84  }
85  // Sets the probability (value in [0, 1]) of starting to render a word with an
86  // underline. This implementation consider words to be space-delimited
87  // sequences of characters.
88  void set_underline_start_prob(const double frac);
89  // Set the probability (value in [0, 1]) of continuing a started underline to
90  // the next word.
91  void set_underline_continuation_prob(const double frac);
92  void set_underline_style(const PangoUnderline style) {
93  underline_style_ = style;
94  }
95  void set_features(const char *features) {
96  features_ = features;
97  }
98  void set_page(int page) {
99  page_ = page;
100  }
101  void set_box_padding(int val) {
102  box_padding_ = val;
103  }
104  void set_drop_uncovered_chars(bool val) {
105  drop_uncovered_chars_ = val;
106  }
108  strip_unrenderable_words_ = val;
109  }
110  void set_output_word_boxes(bool val) {
111  output_word_boxes_ = val;
112  }
113  // Before rendering the string, replace latin characters with their optional
114  // ligatured forms (such as "fi", "ffi" etc.) if the font_ covers those
115  // unicodes.
116  void set_add_ligatures(bool add_ligatures) {
117  add_ligatures_ = add_ligatures;
118  }
119  // Set the rgb value of the text ink. Values range in [0, 1.0]
120  void set_pen_color(double r, double g, double b) {
121  pen_color_[0] = r;
122  pen_color_[1] = g;
123  pen_color_[2] = b;
124  }
125  void set_h_margin(const int h_margin) {
126  h_margin_ = h_margin;
127  }
128  void set_v_margin(const int v_margin) {
129  v_margin_ = v_margin;
130  }
131  const PangoFontInfo &font() const {
132  return font_;
133  }
134  int h_margin() const {
135  return h_margin_;
136  }
137  int v_margin() const {
138  return v_margin_;
139  }
140 
141  // Get the boxchars of all clusters rendered thus far (or since the last call
142  // to ClearBoxes()).
143  const std::vector<BoxChar *> &GetBoxes() const;
144  // Get the rendered page bounding boxes of all pages created thus far (or
145  // since last call to ClearBoxes()).
146  Boxa *GetPageBoxes() const;
147 
148  // Rotate the boxes on the most recent page by the given rotation.
149  void RotatePageBoxes(float rotation);
150  // Delete all boxes.
151  void ClearBoxes();
152  // Returns the boxes in a boxfile string.
153  std::string GetBoxesStr();
154  // Writes the boxes to a boxfile.
155  void WriteAllBoxes(const std::string &filename);
156  // Removes space-delimited words from the string that are not renderable by
157  // the current font and returns the count of such words.
158  int StripUnrenderableWords(std::string *utf8_text) const;
159 
160  // Insert a Word Joiner symbol (U+2060) between adjacent characters, excluding
161  // spaces and combining types, in each word before rendering to ensure words
162  // are not broken across lines. The output boxchars will not contain the
163  // joiner.
164  static std::string InsertWordJoiners(const std::string &text);
165 
166  // Helper functions to convert fullwidth Latin and halfwidth Basic Latin.
167  static std::string ConvertBasicLatinToFullwidthLatin(const std::string &text);
168  static std::string ConvertFullwidthLatinToBasicLatin(const std::string &text);
169 
170 protected:
171  // Init and free local renderer objects.
172  void InitPangoCairo();
173  void FreePangoCairo();
174  // Set rendering properties.
175  void SetLayoutProperties();
176  void SetWordUnderlineAttributes(const std::string &page_text);
177  // Compute bounding boxes around grapheme clusters.
178  void ComputeClusterBoxes();
179  void CorrectBoxPositionsToLayout(std::vector<BoxChar *> *boxchars);
180  bool GetClusterStrings(std::vector<std::string> *cluster_text);
181  int FindFirstPageBreakOffset(const char *text, int text_length);
182 
184  // Page properties
185  int page_width_, page_height_, h_margin_, v_margin_;
186  // Text rendering properties
187  double pen_color_[3];
189  int leading_, resolution_;
195  PangoUnderline underline_style_;
196  std::string features_;
197  // Text filtering options
202  // Pango and cairo specific objects
203  cairo_surface_t *surface_;
204  cairo_t *cr_;
205  PangoLayout *layout_;
206  // Internal state of current page number, updated on successive calls to
207  // RenderToImage()
209  int page_;
210  // Boxes and associated text for all pages rendered with RenderToImage() since
211  // the last call to ClearBoxes().
212  std::vector<BoxChar *> boxchars_;
214  // Bounding boxes for pages since the last call to ClearBoxes().
215  Boxa *page_boxes_;
216 
217  // Objects cached for subsequent calls to RenderAllFontsToImage()
218  std::unordered_map<char32, int64_t> char_map_; // Time-saving char histogram.
219  int total_chars_; // Number in the string to be rendered.
220  unsigned int font_index_; // Index of next font to use in font list.
221  int last_offset_; // Offset returned from last successful rendering
222 
223 private:
224  StringRenderer(const StringRenderer &) = delete;
225  void operator=(const StringRenderer &) = delete;
226 };
227 } // namespace tesseract
228 
229 #endif // THIRD_PARTY_TESSERACT_TRAINING_STRINGRENDERER_H_
void set_features(const char *features)
void set_pen_color(double r, double g, double b)
void set_vertical_text(bool vertical_text)
void set_underline_style(const PangoUnderline style)
void set_render_fullwidth_latin(bool render_fullwidth_latin)
void set_drop_uncovered_chars(bool val)
void set_gravity_hint_strong(bool gravity_hint_strong)
void set_strip_unrenderable_words(bool val)
void set_add_ligatures(bool add_ligatures)
void set_h_margin(const int h_margin)
cairo_surface_t * surface_
std::vector< BoxChar * > boxchars_
void set_char_spacing(int char_spacing)
void set_output_word_boxes(bool val)
void set_v_margin(const int v_margin)
const PangoFontInfo & font() const
std::unordered_map< char32, int64_t > char_map_
PangoUnderline underline_style_
void set_leading(int leading)