lang_model_helpers.h

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// Copyright 2017 Google Inc. All Rights Reserved.
// Author: rays@google.com (Ray Smith)
// Purpose: Collection of convenience functions to simplify creation of the
//          unicharset, recoder, and dawgs for an LSTM model.
 
// 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_LANG_MODEL_HELPERS_H_
#define TESSERACT_TRAINING_LANG_MODEL_HELPERS_H_
 
#include "export.h"
 
#include "serialis.h"
#include "tessdatamanager.h"
#include "unicharset.h"
 
#include <string>
 
namespace tesseract {
 
// Helper makes a filename (<output_dir>/<lang>/<lang><suffix>) and writes data
// to the file, using writer if not null, otherwise, a default writer.
// Default writer will overwrite any existing file, but a supplied writer
// can do its own thing. If lang is empty, returns true but does nothing.
// NOTE that suffix should contain any required . for the filename.
TESS_UNICHARSET_TRAINING_API
bool WriteFile(const std::string &output_dir, const std::string &lang, const std::string &suffix,
               const std::vector<char> &data, FileWriter writer);
// Helper reads a file with optional reader and returns a string.
// On failure emits a warning message and returns and empty string.
TESS_UNICHARSET_TRAINING_API
std::string ReadFile(const std::string &filename, FileReader reader = nullptr);
 
// Helper writes the unicharset to file and to the traineddata.
bool WriteUnicharset(const UNICHARSET &unicharset, const std::string &output_dir,
                     const std::string &lang, FileWriter writer, TessdataManager *traineddata);
// Helper creates the recoder from the unicharset and writes it to the
// traineddata, with a human-readable form to file at:
// <output_dir>/<lang>/<lang>.charset_size=<num> for some num being the size
// of the re-encoded character set. The charset_size file is written using
// writer if not null, or using a default file writer otherwise, overwriting
// any existing content.
// If pass_through is true, then the recoder will be a no-op, passing the
// unicharset codes through unchanged. Otherwise, the recoder will "compress"
// the unicharset by encoding Hangul in Jamos, decomposing multi-unicode
// symbols into sequences of unicodes, and encoding Han using the data in the
// radical_table_data, which must be the content of the file:
// langdata/radical-stroke.txt.
bool WriteRecoder(const UNICHARSET &unicharset, bool pass_through, const std::string &output_dir,
                  const std::string &lang, FileWriter writer, std::string *radical_table_data,
                  TessdataManager *traineddata);
 
// The main function for combine_lang_model.cpp.
// Returns EXIT_SUCCESS or EXIT_FAILURE for error.
// unicharset: can be a hand-created file with incomplete fields. Its basic
//             and script properties will be set before it is used.
// script_dir: should point to the langdata (github repo) directory.
// version_str: arbitrary version label.
// Output files will be written to <output_dir>/<lang>/<lang>.*
// If pass_through_recoder is true, the unicharset will be used unchanged as
// labels in the classifier, otherwise, the unicharset will be "compressed" to
// make the recognition task simpler and faster.
// The words/puncs/numbers lists may be all empty. If any are non-empty then
// puncs must be non-empty.
// lang_is_rtl indicates that the language is generally written from right
// to left (eg Arabic/Hebrew).
TESS_UNICHARSET_TRAINING_API
int CombineLangModel(const UNICHARSET &unicharset, const std::string &script_dir,
                     const std::string &version_str, const std::string &output_dir,
                     const std::string &lang, bool pass_through_recoder,
                     const std::vector<std::string> &words, const std::vector<std::string> &puncs,
                     const std::vector<std::string> &numbers, bool lang_is_rtl, FileReader reader,
                     FileWriter writer);
 
} // namespace tesseract
 
#endif // TESSERACT_TRAINING_LANG_MODEL_HELPERS_H_