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comparison mupdf-source/thirdparty/tesseract/src/training/pango/stringrenderer.h @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
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 }
107 void set_strip_unrenderable_words(bool val) {
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
183 PangoFontInfo font_;
184 // Page properties
185 int page_width_, page_height_, h_margin_, v_margin_;
186 // Text rendering properties
187 double pen_color_[3];
188 int char_spacing_;
189 int leading_, resolution_;
190 bool vertical_text_;
191 bool gravity_hint_strong_;
192 bool render_fullwidth_latin_;
193 double underline_start_prob_;
194 double underline_continuation_prob_;
195 PangoUnderline underline_style_;
196 std::string features_;
197 // Text filtering options
198 bool drop_uncovered_chars_;
199 bool strip_unrenderable_words_;
200 bool add_ligatures_;
201 bool output_word_boxes_;
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()
208 int start_box_;
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_;
213 int box_padding_;
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_