/usr/include/tesseract/char_bigrams.h is in libtesseract-dev 3.02.01-6.
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* File: char_bigrams.h
* Description: Declaration of a Character Bigrams Class
* Author: Ahmad Abdulkader
* Created: 2007
*
* (C) Copyright 2008, 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.
*
**********************************************************************/
// The CharBigram class represents the interface to the character bigram
// table used by Cube
// A CharBigram object can be constructed from the Char Bigrams file
// Given a sequence of characters, the "Cost" method returns the Char Bigram
// cost of the string according to the table
#ifndef CHAR_BIGRAMS_H
#define CHAR_BIGRAMS_H
#include <string>
#include "char_set.h"
namespace tesseract {
// structure representing a single bigram value
struct Bigram {
int cnt;
int cost;
};
// structure representing the char bigram array of characters
// following a specific character
struct CharBigram {
int total_cnt;
char_32 max_char;
Bigram *bigram;
};
// structure representing the whole bigram table
struct CharBigramTable {
int total_cnt;
int worst_cost;
char_32 max_char;
CharBigram *char_bigram;
};
class CharBigrams {
public:
CharBigrams();
~CharBigrams();
// Construct the CharBigrams class from a file
static CharBigrams *Create(const string &data_file_path,
const string &lang);
// Top-level function to return the mean character bigram cost of a
// sequence of characters. If char_set is not NULL, use
// tesseract functions to return a case-invariant cost.
// This avoids unnecessarily penalizing all-one-case words or
// capitalized words (first-letter upper-case and remaining letters
// lower-case).
int Cost(const char_32 *str, CharSet *char_set) const;
protected:
// Returns the character bigram cost of two characters.
int PairCost(char_32 ch1, char_32 ch2) const;
// Returns the mean character bigram cost of a sequence of
// characters. Adds a space at the beginning and end to account for
// cost of starting and ending characters.
int MeanCostWithSpaces(const char_32 *char_32_ptr) const;
private:
// Only words this length or greater qualify for case-invariant character
// bigram cost.
static const int kMinLengthCaseInvariant = 4;
CharBigramTable bigram_table_;
};
}
#endif // CHAR_BIGRAMS_H
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