tesseract/training/stringrenderer.h
2017-06-02 09:58:26 +02:00

225 lines
8.1 KiB
C++

/**********************************************************************
* File: stringrenderer.h
* Description: Class for rendering UTF-8 text to an image, and retrieving
* bounding boxes around each grapheme cluster.
*
* Instances are created using a font description string
* (eg. "Arial Italic 12"; see pango_font_info.h for the format)
* and the page dimensions. Other renderer properties such as
* spacing, ligaturization, as well a preprocessing behavior such
* as removal of unrenderable words and a special n-gram mode may
* be set using respective set_* methods.
*
* Author: Ranjith Unnikrishnan
* Created: Mon Nov 18 2013
*
* (C) Copyright 2013, Google Inc.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
**********************************************************************/
#ifndef TESSERACT_TRAINING_STRINGRENDERER_H_
#define TESSERACT_TRAINING_STRINGRENDERER_H_
#include <string>
#include <unordered_map>
#include <vector>
#include "host.h"
#include "pango_font_info.h"
#include "pango/pango-layout.h"
#include "pango/pangocairo.h"
struct Boxa;
struct Pix;
namespace tesseract {
class BoxChar;
class StringRenderer {
public:
StringRenderer(const string& font_desc, int page_width, int page_height);
~StringRenderer();
// Renders the text with the chosen font and returns the byte offset up to
// which the text could be rendered so as to fit the specified page
// dimensions.
int RenderToImage(const char* text, int text_length, Pix** pix);
int RenderToGrayscaleImage(const char* text, int text_length, Pix** pix);
int RenderToBinaryImage(const char* text, int text_length, int threshold,
Pix** pix);
// Renders a line of text with all available fonts that were able to render
// at least min_coverage fraction of the input text. Use 1.0 to require that
// a font be able to render all the text.
int RenderAllFontsToImage(double min_coverage, const char* text,
int text_length, string* font_used, Pix** pix);
bool set_font(const string& desc);
void set_char_spacing(double char_spacing) {
char_spacing_ = char_spacing;
}
void set_leading(int leading) {
leading_ = leading;
}
void set_resolution(const int resolution);
void set_vertical_text(bool vertical_text) {
vertical_text_ = vertical_text;
}
void set_gravity_hint_strong(bool gravity_hint_strong) {
gravity_hint_strong_ = gravity_hint_strong;
}
void set_render_fullwidth_latin(bool render_fullwidth_latin) {
render_fullwidth_latin_ = render_fullwidth_latin;
}
// Sets the probability (value in [0, 1]) of starting to render a word with an
// underline. This implementation consider words to be space-delimited
// sequences of characters.
void set_underline_start_prob(const double frac);
// Set the probability (value in [0, 1]) of continuing a started underline to
// the next word.
void set_underline_continuation_prob(const double frac);
void set_underline_style(const PangoUnderline style) {
underline_style_ = style;
}
void set_features(const char* features) {
free(features_);
features_ = strdup(features);
}
void set_page(int page) {
page_ = page;
}
void set_box_padding(int val) {
box_padding_ = val;
}
void set_drop_uncovered_chars(bool val) {
drop_uncovered_chars_ = val;
}
void set_strip_unrenderable_words(bool val) {
strip_unrenderable_words_ = val;
}
void set_output_word_boxes(bool val) {
output_word_boxes_ = val;
}
// Before rendering the string, replace latin characters with their optional
// ligatured forms (such as "fi", "ffi" etc.) if the font_ covers those
// unicodes.
void set_add_ligatures(bool add_ligatures) {
add_ligatures_ = add_ligatures;
}
// Set the rgb value of the text ink. Values range in [0, 1.0]
void set_pen_color(double r, double g, double b) {
pen_color_[0] = r;
pen_color_[1] = g;
pen_color_[2] = b;
}
void set_h_margin(const int h_margin) {
h_margin_ = h_margin;
}
void set_v_margin(const int v_margin) {
v_margin_ = v_margin;
}
const PangoFontInfo& font() const {
return font_;
}
int h_margin() const { return h_margin_; }
int v_margin() const { return v_margin_; }
// Get the boxchars of all clusters rendered thus far (or since the last call
// to ClearBoxes()).
const std::vector<BoxChar*>& GetBoxes() const;
// Get the rendered page bounding boxes of all pages created thus far (or
// since last call to ClearBoxes()).
Boxa* GetPageBoxes() const;
// Rotate the boxes on the most recent page by the given rotation.
void RotatePageBoxes(float rotation);
// Delete all boxes.
void ClearBoxes();
// Returns the boxes in a boxfile string.
string GetBoxesStr();
// Writes the boxes to a boxfile.
void WriteAllBoxes(const string& filename);
// Removes space-delimited words from the string that are not renderable by
// the current font and returns the count of such words.
int StripUnrenderableWords(string* utf8_text) const;
// Insert a Word Joiner symbol (U+2060) between adjacent characters, excluding
// spaces and combining types, in each word before rendering to ensure words
// are not broken across lines. The output boxchars will not contain the
// joiner.
static string InsertWordJoiners(const string& text);
// Helper functions to convert fullwidth Latin and halfwidth Basic Latin.
static string ConvertBasicLatinToFullwidthLatin(const string& text);
static string ConvertFullwidthLatinToBasicLatin(const string& text);
protected:
// Init and free local renderer objects.
void InitPangoCairo();
void FreePangoCairo();
// Set rendering properties.
void SetLayoutProperties();
void SetWordUnderlineAttributes(const string& page_text);
// Compute bounding boxes around grapheme clusters.
void ComputeClusterBoxes();
void CorrectBoxPositionsToLayout(std::vector<BoxChar*>* boxchars);
bool GetClusterStrings(std::vector<string>* cluster_text);
int FindFirstPageBreakOffset(const char* text, int text_length);
PangoFontInfo font_;
// Page properties
int page_width_, page_height_, h_margin_, v_margin_;
// Text rendering properties
double pen_color_[3];
double char_spacing_;
int leading_, resolution_;
bool vertical_text_;
bool gravity_hint_strong_;
bool render_fullwidth_latin_;
double underline_start_prob_;
double underline_continuation_prob_;
PangoUnderline underline_style_;
char* features_;
// Text filtering options
bool drop_uncovered_chars_;
bool strip_unrenderable_words_;
bool add_ligatures_;
bool output_word_boxes_;
// Pango and cairo specific objects
cairo_surface_t* surface_;
cairo_t* cr_;
PangoLayout* layout_;
// Internal state of current page number, updated on successive calls to
// RenderToImage()
int start_box_;
int page_;
// Boxes and associated text for all pages rendered with RenderToImage() since
// the last call to ClearBoxes().
std::vector<BoxChar*> boxchars_;
int box_padding_;
// Bounding boxes for pages since the last call to ClearBoxes().
Boxa* page_boxes_;
// Objects cached for subsequent calls to RenderAllFontsToImage()
std::unordered_map<char32, inT64> char_map_; // Time-saving char histogram.
int total_chars_; // Number in the string to be rendered.
int font_index_; // Index of next font to use in font list.
int last_offset_; // Offset returned from last successful rendering
private:
StringRenderer(const StringRenderer&);
void operator=(const StringRenderer&);
};
} // namespace tesseract
#endif // THIRD_PARTY_TESSERACT_TRAINING_STRINGRENDERER_H_