ambigs.h

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// File:        ambigs.h
// Description: Constants, flags, functions for dealing with
//              ambiguities (training and recognition).
// Author:      Daria Antonova
//
// (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.
//
 
#ifndef TESSERACT_CCUTIL_AMBIGS_H_
#define TESSERACT_CCUTIL_AMBIGS_H_
 
#ifdef HAVE_CONFIG_H
#  include "config_auto.h" // DISABLED_LEGACY_ENGINE
#endif
 
#if !defined(DISABLED_LEGACY_ENGINE)
 
#  include <tesseract/unichar.h>
#  include "elst.h"
#  include "tprintf.h"
#  include "unicharset.h"
 
#  define MAX_AMBIG_SIZE 10
 
namespace tesseract {
 
using UnicharIdVector = std::vector<UNICHAR_ID>;
 
enum AmbigType {
  NOT_AMBIG,      // the ngram pair is not ambiguous
  REPLACE_AMBIG,  // ocred ngram should always be substituted with correct
  DEFINITE_AMBIG, // add correct ngram to the classifier results (1-1)
  SIMILAR_AMBIG,  // use pairwise classifier for ocred/correct pair (1-1)
  CASE_AMBIG,     // this is a case ambiguity (1-1)
 
  AMBIG_TYPE_COUNT // number of enum entries
};
 
// A collection of utility functions for arrays of UNICHAR_IDs that are
// terminated by INVALID_UNICHAR_ID.
class UnicharIdArrayUtils {
public:
  // Compares two arrays of unichar ids. Returns -1 if the length of array1 is
  // less than length of array2, if any array1[i] is less than array2[i].
  // Returns 0 if the arrays are equal, 1 otherwise.
  // The function assumes that the arrays are terminated by INVALID_UNICHAR_ID.
  static inline int compare(const UNICHAR_ID *ptr1, const UNICHAR_ID *ptr2) {
    for (;;) {
      const UNICHAR_ID val1 = *ptr1++;
      const UNICHAR_ID val2 = *ptr2++;
      if (val1 != val2) {
        if (val1 == INVALID_UNICHAR_ID) {
          return -1;
        }
        if (val2 == INVALID_UNICHAR_ID) {
          return 1;
        }
        if (val1 < val2) {
          return -1;
        }
        return 1;
      }
      if (val1 == INVALID_UNICHAR_ID) {
        return 0;
      }
    }
  }
 
  // Copies UNICHAR_IDs from dst to src. Returns the number of ids copied.
  // The function assumes that the arrays are terminated by INVALID_UNICHAR_ID
  // and that dst has enough space for all the elements from src.
  static inline int copy(const UNICHAR_ID src[], UNICHAR_ID dst[]) {
    int i = 0;
    do {
      dst[i] = src[i];
    } while (dst[i++] != INVALID_UNICHAR_ID);
    return i - 1;
  }
 
  // Prints unichars corresponding to the unichar_ids in the given array.
  // The function assumes that array is terminated by INVALID_UNICHAR_ID.
  static inline void print(const UNICHAR_ID array[], const UNICHARSET &unicharset) {
    const UNICHAR_ID *ptr = array;
    if (*ptr == INVALID_UNICHAR_ID) {
      tprintf("[Empty]");
    }
    while (*ptr != INVALID_UNICHAR_ID) {
      tprintf("%s ", unicharset.id_to_unichar(*ptr++));
    }
    tprintf("( ");
    ptr = array;
    while (*ptr != INVALID_UNICHAR_ID) {
      tprintf("%d ", *ptr++);
    }
    tprintf(")\n");
  }
};
 
// AMBIG_SPEC_LIST stores a list of dangerous ambigs that
// start with the same unichar (e.g. r->t rn->m rr1->m).
class AmbigSpec : public ELIST_LINK {
public:
  AmbigSpec();
  ~AmbigSpec() = default;
 
  // Comparator function for sorting AmbigSpec_LISTs. The lists will
  // be sorted by their wrong_ngram arrays. Example of wrong_ngram vectors
  // in a sorted AmbigSpec_LIST: [9 1 3], [9 3 4], [9 8], [9, 8 1].
  static int compare_ambig_specs(const void *spec1, const void *spec2) {
    const AmbigSpec *s1 = *static_cast<const AmbigSpec *const *>(spec1);
    const AmbigSpec *s2 = *static_cast<const AmbigSpec *const *>(spec2);
    int result = UnicharIdArrayUtils::compare(s1->wrong_ngram, s2->wrong_ngram);
    if (result != 0) {
      return result;
    }
    return UnicharIdArrayUtils::compare(s1->correct_fragments, s2->correct_fragments);
  }
 
  UNICHAR_ID wrong_ngram[MAX_AMBIG_SIZE + 1];
  UNICHAR_ID correct_fragments[MAX_AMBIG_SIZE + 1];
  UNICHAR_ID correct_ngram_id;
  AmbigType type;
  int wrong_ngram_size;
};
ELISTIZEH(AmbigSpec)
 
// AMBIG_TABLE[i] stores a set of ambiguities whose
// wrong ngram starts with unichar id i.
using UnicharAmbigsVector = std::vector<AmbigSpec_LIST *>;
 
class UnicharAmbigs {
public:
  UnicharAmbigs() = default;
  ~UnicharAmbigs() {
    for (auto data : replace_ambigs_) {
      delete data;
    }
    for (auto data : dang_ambigs_) {
      delete data;
    }
    for (auto data : one_to_one_definite_ambigs_) {
      delete data;
    }
  }
 
  const UnicharAmbigsVector &dang_ambigs() const {
    return dang_ambigs_;
  }
  const UnicharAmbigsVector &replace_ambigs() const {
    return replace_ambigs_;
  }
 
  // Initializes the ambigs by adding a nullptr pointer to each table.
  void InitUnicharAmbigs(const UNICHARSET &unicharset, bool use_ambigs_for_adaption);
 
  // Loads the universal ambigs that are useful for any language.
  void LoadUniversal(const UNICHARSET &encoder_set, UNICHARSET *unicharset);
 
  // Fills in two ambiguity tables (replaceable and dangerous) with information
  // read from the ambigs file. An ambiguity table is an array of lists.
  // The array is indexed by a class id. Each entry in the table provides
  // a list of potential ambiguities which can start with the corresponding
  // character. For example the ambiguity "rn -> m", would be located in the
  // table at index of unicharset.unichar_to_id('r').
  // In 1-1 ambiguities (e.g. s -> S, 1 -> I) are recorded in
  // one_to_one_definite_ambigs_. This vector is also indexed by the class id
  // of the wrong part of the ambiguity and each entry contains a vector of
  // unichar ids that are ambiguous to it.
  // encoder_set is used to encode the ambiguity strings, undisturbed by new
  // unichar_ids that may be created by adding the ambigs.
  void LoadUnicharAmbigs(const UNICHARSET &encoder_set, TFile *ambigs_file, int debug_level,
                         bool use_ambigs_for_adaption, UNICHARSET *unicharset);
 
  // Returns definite 1-1 ambigs for the given unichar id.
  inline const UnicharIdVector *OneToOneDefiniteAmbigs(UNICHAR_ID unichar_id) const {
    if (one_to_one_definite_ambigs_.empty()) {
      return nullptr;
    }
    return one_to_one_definite_ambigs_[unichar_id];
  }
 
  // Returns a pointer to the vector with all unichar ids that appear in the
  // 'correct' part of the ambiguity pair when the given unichar id appears
  // in the 'wrong' part of the ambiguity. E.g. if DangAmbigs file consist of
  // m->rn,rn->m,m->iii, UnicharAmbigsForAdaption() called with unichar id of
  // m will return a pointer to a vector with unichar ids of r,n,i.
  inline const UnicharIdVector *AmbigsForAdaption(UNICHAR_ID unichar_id) const {
    if (ambigs_for_adaption_.empty()) {
      return nullptr;
    }
    return ambigs_for_adaption_[unichar_id];
  }
 
  // Similar to the above, but return the vector of unichar ids for which
  // the given unichar_id is an ambiguity (appears in the 'wrong' part of
  // some ambiguity pair).
  inline const UnicharIdVector *ReverseAmbigsForAdaption(UNICHAR_ID unichar_id) const {
    if (reverse_ambigs_for_adaption_.empty()) {
      return nullptr;
    }
    return reverse_ambigs_for_adaption_[unichar_id];
  }
 
private:
  bool ParseAmbiguityLine(int line_num, int version, int debug_level, const UNICHARSET &unicharset,
                          char *buffer, int *test_ambig_part_size, UNICHAR_ID *test_unichar_ids,
                          int *replacement_ambig_part_size, char *replacement_string, int *type);
  bool InsertIntoTable(UnicharAmbigsVector &table, int test_ambig_part_size,
                       UNICHAR_ID *test_unichar_ids, int replacement_ambig_part_size,
                       const char *replacement_string, int type, AmbigSpec *ambig_spec,
                       UNICHARSET *unicharset);
 
  UnicharAmbigsVector dang_ambigs_;
  UnicharAmbigsVector replace_ambigs_;
  std::vector<UnicharIdVector *> one_to_one_definite_ambigs_;
  std::vector<UnicharIdVector *> ambigs_for_adaption_;
  std::vector<UnicharIdVector *> reverse_ambigs_for_adaption_;
};
 
} // namespace tesseract
 
#endif // !defined(DISABLED_LEGACY_ENGINE)
 
#endif // TESSERACT_CCUTIL_AMBIGS_H_