tesseract/src/training/ligature_table.h

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/**********************************************************************
* File: ligature_table.h
* Description: Class for adding and removing optional latin ligatures,
* conditional on codepoint support by a specified font
* (if specified).
* 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 TRAININGDATA_LIGATURE_TABLE_H_
#define TRAININGDATA_LIGATURE_TABLE_H_
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#include <memory>
#include <string>
#include <unordered_map>
#include "util.h"
namespace tesseract {
class PangoFontInfo; // defined in pango_font_info.h
// Map to substitute strings for ligatures.
typedef std::unordered_map<std::string, std::string, StringHash> LigHash;
class LigatureTable {
public:
// Get a static instance of this class.
static LigatureTable* Get();
// Convert the utf8 string so that ligaturizable sequences, such as "fi" get
// replaced by the (utf8 code for) appropriate ligature characters. Only do so
// if the corresponding ligature character is renderable in the current font.
std::string AddLigatures(const std::string& str, const PangoFontInfo* font) const;
// Remove all ligatures.
std::string RemoveLigatures(const std::string& str) const;
// Remove only custom ligatures (eg. "ct") encoded in the private-use-area.
std::string RemoveCustomLigatures(const std::string& str) const;
const LigHash& norm_to_lig_table() const {
return norm_to_lig_table_;
}
const LigHash& lig_to_norm_table() const {
return lig_to_norm_table_;
}
protected:
LigatureTable();
// Initialize the hash tables mapping between ligature strings and the
// corresponding ligature characters.
void Init();
static std::unique_ptr<LigatureTable> instance_;
LigHash norm_to_lig_table_;
LigHash lig_to_norm_table_;
int min_lig_length_;
int max_lig_length_;
int min_norm_length_;
int max_norm_length_;
private:
LigatureTable(const LigatureTable&);
void operator=(const LigatureTable&);
};
} // namespace tesseract
#endif // OCR_TRAININGDATA_TYPESETTING_LIGATURE_TABLE_H_