superscript.cpp

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/******************************************************************
 * File:        superscript.cpp
 * Description: Correction pass to fix superscripts and subscripts.
 * Author:      David Eger
 *
 * (C) Copyright 2012, 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.
 *
 **********************************************************************/
 
#include "normalis.h"
#include "tesseractclass.h"
 
namespace tesseract {
 
static int LeadingUnicharsToChopped(WERD_RES *word, int num_unichars) {
  int num_chopped = 0;
  for (int i = 0; i < num_unichars; i++) {
    num_chopped += word->best_state[i];
  }
  return num_chopped;
}
 
static int TrailingUnicharsToChopped(WERD_RES *word, int num_unichars) {
  int num_chopped = 0;
  for (int i = 0; i < num_unichars; i++) {
    num_chopped += word->best_state[word->best_state.size() - 1 - i];
  }
  return num_chopped;
}
 
static void YOutlierPieces(WERD_RES *word, int rebuilt_blob_index, int super_y_bottom,
                           int sub_y_top, ScriptPos *leading_pos, int *num_leading_outliers,
                           ScriptPos *trailing_pos, int *num_trailing_outliers) {
  ScriptPos sp_unused1, sp_unused2;
  int unused1, unused2;
  if (!leading_pos) {
    leading_pos = &sp_unused1;
  }
  if (!num_leading_outliers) {
    num_leading_outliers = &unused1;
  }
  if (!trailing_pos) {
    trailing_pos = &sp_unused2;
  }
  if (!num_trailing_outliers) {
    num_trailing_outliers = &unused2;
  }
 
  *num_leading_outliers = *num_trailing_outliers = 0;
  *leading_pos = *trailing_pos = SP_NORMAL;
 
  int chopped_start = LeadingUnicharsToChopped(word, rebuilt_blob_index);
  int num_chopped_pieces = word->best_state[rebuilt_blob_index];
  ScriptPos last_pos = SP_NORMAL;
  int trailing_outliers = 0;
  for (int i = 0; i < num_chopped_pieces; i++) {
    TBOX box = word->chopped_word->blobs[chopped_start + i]->bounding_box();
    ScriptPos pos = SP_NORMAL;
    if (box.bottom() >= super_y_bottom) {
      pos = SP_SUPERSCRIPT;
    } else if (box.top() <= sub_y_top) {
      pos = SP_SUBSCRIPT;
    }
    if (pos == SP_NORMAL) {
      if (trailing_outliers == i) {
        *num_leading_outliers = trailing_outliers;
        *leading_pos = last_pos;
      }
      trailing_outliers = 0;
    } else {
      if (pos == last_pos) {
        trailing_outliers++;
      } else {
        trailing_outliers = 1;
      }
    }
    last_pos = pos;
  }
  *num_trailing_outliers = trailing_outliers;
  *trailing_pos = last_pos;
}
 
bool Tesseract::SubAndSuperscriptFix(WERD_RES *word) {
  if (word->tess_failed || word->word->flag(W_REP_CHAR) || !word->best_choice) {
    return false;
  }
  int num_leading, num_trailing;
  ScriptPos sp_leading, sp_trailing;
  float leading_certainty, trailing_certainty;
  float avg_certainty, unlikely_threshold;
 
  // Calculate the number of whole suspicious characters at the edges.
  GetSubAndSuperscriptCandidates(word, &num_leading, &sp_leading, &leading_certainty, &num_trailing,
                                 &sp_trailing, &trailing_certainty, &avg_certainty,
                                 &unlikely_threshold);
 
  const char *leading_pos = sp_leading == SP_SUBSCRIPT ? "sub" : "super";
  const char *trailing_pos = sp_trailing == SP_SUBSCRIPT ? "sub" : "super";
 
  int num_blobs = word->best_choice->length();
 
  // Calculate the remainder (partial characters) at the edges.
  // This accounts for us having classified the best version of
  // a word as [speaker?'] when it was instead [speaker.^{21}]
  // (that is we accidentally thought the 2 was attached to the period).
  int num_remainder_leading = 0, num_remainder_trailing = 0;
  if (num_leading + num_trailing < num_blobs && unlikely_threshold < 0.0) {
    int super_y_bottom = kBlnBaselineOffset + kBlnXHeight * superscript_min_y_bottom;
    int sub_y_top = kBlnBaselineOffset + kBlnXHeight * subscript_max_y_top;
    int last_word_char = num_blobs - 1 - num_trailing;
    float last_char_certainty = word->best_choice->certainty(last_word_char);
    if (word->best_choice->unichar_id(last_word_char) != 0 &&
        last_char_certainty <= unlikely_threshold) {
      ScriptPos rpos;
      YOutlierPieces(word, last_word_char, super_y_bottom, sub_y_top, nullptr, nullptr, &rpos,
                     &num_remainder_trailing);
      if (num_trailing > 0 && rpos != sp_trailing) {
        num_remainder_trailing = 0;
      }
      if (num_remainder_trailing > 0 && last_char_certainty < trailing_certainty) {
        trailing_certainty = last_char_certainty;
      }
    }
    bool another_blob_available =
        (num_remainder_trailing == 0) || num_leading + num_trailing + 1 < num_blobs;
    int first_char_certainty = word->best_choice->certainty(num_leading);
    if (another_blob_available && word->best_choice->unichar_id(num_leading) != 0 &&
        first_char_certainty <= unlikely_threshold) {
      ScriptPos lpos;
      YOutlierPieces(word, num_leading, super_y_bottom, sub_y_top, &lpos, &num_remainder_leading,
                     nullptr, nullptr);
      if (num_leading > 0 && lpos != sp_leading) {
        num_remainder_leading = 0;
      }
      if (num_remainder_leading > 0 && first_char_certainty < leading_certainty) {
        leading_certainty = first_char_certainty;
      }
    }
  }
 
  // If nothing to do, bail now.
  if (num_leading + num_trailing + num_remainder_leading + num_remainder_trailing == 0) {
    return false;
  }
 
  if (superscript_debug >= 1) {
    tprintf("Candidate for superscript detection: %s (",
            word->best_choice->unichar_string().c_str());
    if (num_leading || num_remainder_leading) {
      tprintf("%d.%d %s-leading ", num_leading, num_remainder_leading, leading_pos);
    }
    if (num_trailing || num_remainder_trailing) {
      tprintf("%d.%d %s-trailing ", num_trailing, num_remainder_trailing, trailing_pos);
    }
    tprintf(")\n");
  }
  if (superscript_debug >= 3) {
    word->best_choice->print();
  }
  if (superscript_debug >= 2) {
    tprintf(" Certainties -- Average: %.2f  Unlikely thresh: %.2f  ", avg_certainty,
            unlikely_threshold);
    if (num_leading) {
      tprintf("Orig. leading (min): %.2f  ", leading_certainty);
    }
    if (num_trailing) {
      tprintf("Orig. trailing (min): %.2f  ", trailing_certainty);
    }
    tprintf("\n");
  }
 
  // We've now calculated the number of rebuilt blobs we want to carve off.
  // However, split_word() works from TBLOBs in chopped_word, so we need to
  // convert to those.
  int num_chopped_leading = LeadingUnicharsToChopped(word, num_leading) + num_remainder_leading;
  int num_chopped_trailing = TrailingUnicharsToChopped(word, num_trailing) + num_remainder_trailing;
 
  int retry_leading = 0;
  int retry_trailing = 0;
  bool is_good = false;
  WERD_RES *revised = TrySuperscriptSplits(num_chopped_leading, leading_certainty, sp_leading,
                                           num_chopped_trailing, trailing_certainty, sp_trailing,
                                           word, &is_good, &retry_leading, &retry_trailing);
  if (is_good) {
    word->ConsumeWordResults(revised);
  } else if (retry_leading || retry_trailing) {
    int retry_chopped_leading = LeadingUnicharsToChopped(revised, retry_leading);
    int retry_chopped_trailing = TrailingUnicharsToChopped(revised, retry_trailing);
    WERD_RES *revised2 = TrySuperscriptSplits(
        retry_chopped_leading, leading_certainty, sp_leading, retry_chopped_trailing,
        trailing_certainty, sp_trailing, revised, &is_good, &retry_leading, &retry_trailing);
    if (is_good) {
      word->ConsumeWordResults(revised2);
    }
    delete revised2;
  }
  delete revised;
  return is_good;
}
 
void Tesseract::GetSubAndSuperscriptCandidates(const WERD_RES *word, int *num_rebuilt_leading,
                                               ScriptPos *leading_pos, float *leading_certainty,
                                               int *num_rebuilt_trailing, ScriptPos *trailing_pos,
                                               float *trailing_certainty, float *avg_certainty,
                                               float *unlikely_threshold) {
  *avg_certainty = *unlikely_threshold = 0.0f;
  *num_rebuilt_leading = *num_rebuilt_trailing = 0;
  *leading_certainty = *trailing_certainty = 0.0f;
 
  int super_y_bottom = kBlnBaselineOffset + kBlnXHeight * superscript_min_y_bottom;
  int sub_y_top = kBlnBaselineOffset + kBlnXHeight * subscript_max_y_top;
 
  // Step one: Get an average certainty for "normally placed" characters.
 
  // Counts here are of blobs in the rebuild_word / unichars in best_choice.
  *leading_pos = *trailing_pos = SP_NORMAL;
  int leading_outliers = 0;
  int trailing_outliers = 0;
  int num_normal = 0;
  float normal_certainty_total = 0.0f;
  float worst_normal_certainty = 0.0f;
  ScriptPos last_pos = SP_NORMAL;
  int num_blobs = word->rebuild_word->NumBlobs();
  for (int b = 0; b < num_blobs; ++b) {
    TBOX box = word->rebuild_word->blobs[b]->bounding_box();
    ScriptPos pos = SP_NORMAL;
    if (box.bottom() >= super_y_bottom) {
      pos = SP_SUPERSCRIPT;
    } else if (box.top() <= sub_y_top) {
      pos = SP_SUBSCRIPT;
    }
    if (pos == SP_NORMAL) {
      if (word->best_choice->unichar_id(b) != 0) {
        float char_certainty = word->best_choice->certainty(b);
        if (char_certainty < worst_normal_certainty) {
          worst_normal_certainty = char_certainty;
        }
        num_normal++;
        normal_certainty_total += char_certainty;
      }
      if (trailing_outliers == b) {
        leading_outliers = trailing_outliers;
        *leading_pos = last_pos;
      }
      trailing_outliers = 0;
    } else {
      if (last_pos == pos) {
        trailing_outliers++;
      } else {
        trailing_outliers = 1;
      }
    }
    last_pos = pos;
  }
  *trailing_pos = last_pos;
  if (num_normal >= 3) { // throw out the worst as an outlier.
    num_normal--;
    normal_certainty_total -= worst_normal_certainty;
  }
  if (num_normal > 0) {
    *avg_certainty = normal_certainty_total / num_normal;
    *unlikely_threshold = superscript_worse_certainty * (*avg_certainty);
  }
  if (num_normal == 0 || (leading_outliers == 0 && trailing_outliers == 0)) {
    return;
  }
 
  // Step two: Try to split off bits of the word that are both outliers
  //           and have much lower certainty than average
  // Calculate num_leading and leading_certainty.
  for (*leading_certainty = 0.0f, *num_rebuilt_leading = 0; *num_rebuilt_leading < leading_outliers;
       (*num_rebuilt_leading)++) {
    float char_certainty = word->best_choice->certainty(*num_rebuilt_leading);
    if (char_certainty > *unlikely_threshold) {
      break;
    }
    if (char_certainty < *leading_certainty) {
      *leading_certainty = char_certainty;
    }
  }
 
  // Calculate num_trailing and trailing_certainty.
  for (*trailing_certainty = 0.0f, *num_rebuilt_trailing = 0;
       *num_rebuilt_trailing < trailing_outliers; (*num_rebuilt_trailing)++) {
    int blob_idx = num_blobs - 1 - *num_rebuilt_trailing;
    float char_certainty = word->best_choice->certainty(blob_idx);
    if (char_certainty > *unlikely_threshold) {
      break;
    }
    if (char_certainty < *trailing_certainty) {
      *trailing_certainty = char_certainty;
    }
  }
}
 
WERD_RES *Tesseract::TrySuperscriptSplits(int num_chopped_leading, float leading_certainty,
                                          ScriptPos leading_pos, int num_chopped_trailing,
                                          float trailing_certainty, ScriptPos trailing_pos,
                                          WERD_RES *word, bool *is_good, int *retry_rebuild_leading,
                                          int *retry_rebuild_trailing) {
  int num_chopped = word->chopped_word->NumBlobs();
 
  *retry_rebuild_leading = *retry_rebuild_trailing = 0;
 
  // Chop apart the word into up to three pieces.
 
  BlamerBundle *bb0 = nullptr;
  BlamerBundle *bb1 = nullptr;
  WERD_RES *prefix = nullptr;
  WERD_RES *core = nullptr;
  WERD_RES *suffix = nullptr;
  if (num_chopped_leading > 0) {
    prefix = new WERD_RES(*word);
    split_word(prefix, num_chopped_leading, &core, &bb0);
  } else {
    core = new WERD_RES(*word);
  }
 
  if (num_chopped_trailing > 0) {
    int split_pt = num_chopped - num_chopped_trailing - num_chopped_leading;
    split_word(core, split_pt, &suffix, &bb1);
  }
 
  //  Recognize the pieces in turn.
  int saved_cp_multiplier = classify_class_pruner_multiplier;
  int saved_im_multiplier = classify_integer_matcher_multiplier;
  if (prefix) {
    // Turn off Tesseract's y-position penalties for the leading superscript.
    classify_class_pruner_multiplier.set_value(0);
    classify_integer_matcher_multiplier.set_value(0);
 
    // Adjust our expectations about the baseline for this prefix.
    if (superscript_debug >= 3) {
      tprintf(" recognizing first %d chopped blobs\n", num_chopped_leading);
    }
    recog_word_recursive(prefix);
    if (superscript_debug >= 2) {
      tprintf(" The leading bits look like %s %s\n", ScriptPosToString(leading_pos),
              prefix->best_choice->unichar_string().c_str());
    }
 
    // Restore the normal y-position penalties.
    classify_class_pruner_multiplier.set_value(saved_cp_multiplier);
    classify_integer_matcher_multiplier.set_value(saved_im_multiplier);
  }
 
  if (superscript_debug >= 3) {
    tprintf(" recognizing middle %d chopped blobs\n",
            num_chopped - num_chopped_leading - num_chopped_trailing);
  }
 
  if (suffix) {
    // Turn off Tesseract's y-position penalties for the trailing superscript.
    classify_class_pruner_multiplier.set_value(0);
    classify_integer_matcher_multiplier.set_value(0);
 
    if (superscript_debug >= 3) {
      tprintf(" recognizing last %d chopped blobs\n", num_chopped_trailing);
    }
    recog_word_recursive(suffix);
    if (superscript_debug >= 2) {
      tprintf(" The trailing bits look like %s %s\n", ScriptPosToString(trailing_pos),
              suffix->best_choice->unichar_string().c_str());
    }
 
    // Restore the normal y-position penalties.
    classify_class_pruner_multiplier.set_value(saved_cp_multiplier);
    classify_integer_matcher_multiplier.set_value(saved_im_multiplier);
  }
 
  // Evaluate whether we think the results are believably better
  // than what we already had.
  bool good_prefix =
      !prefix || BelievableSuperscript(superscript_debug >= 1, *prefix,
                                       superscript_bettered_certainty * leading_certainty,
                                       retry_rebuild_leading, nullptr);
  bool good_suffix =
      !suffix || BelievableSuperscript(superscript_debug >= 1, *suffix,
                                       superscript_bettered_certainty * trailing_certainty, nullptr,
                                       retry_rebuild_trailing);
 
  *is_good = good_prefix && good_suffix;
  if (!*is_good && !*retry_rebuild_leading && !*retry_rebuild_trailing) {
    // None of it is any good. Quit now.
    delete core;
    delete prefix;
    delete suffix;
    delete bb1;
    return nullptr;
  }
  recog_word_recursive(core);
 
  // Now paste the results together into core.
  if (suffix) {
    suffix->SetAllScriptPositions(trailing_pos);
    join_words(core, suffix, bb1);
  }
  if (prefix) {
    prefix->SetAllScriptPositions(leading_pos);
    join_words(prefix, core, bb0);
    core = prefix;
    prefix = nullptr;
  }
 
  if (superscript_debug >= 1) {
    tprintf("%s superscript fix: %s\n", *is_good ? "ACCEPT" : "REJECT",
            core->best_choice->unichar_string().c_str());
  }
  return core;
}
 
bool Tesseract::BelievableSuperscript(bool debug, const WERD_RES &word, float certainty_threshold,
                                      int *left_ok, int *right_ok) const {
  unsigned initial_ok_run_count = 0;
  unsigned ok_run_count = 0;
  float worst_certainty = 0.0f;
  const WERD_CHOICE &wc = *word.best_choice;
 
  const UnicityTable<FontInfo> &fontinfo_table = get_fontinfo_table();
  for (unsigned i = 0; i < wc.length(); i++) {
    TBLOB *blob = word.rebuild_word->blobs[i];
    UNICHAR_ID unichar_id = wc.unichar_id(i);
    float char_certainty = wc.certainty(i);
    bool bad_certainty = char_certainty < certainty_threshold;
    bool is_punc = wc.unicharset()->get_ispunctuation(unichar_id);
    bool is_italic = word.fontinfo && word.fontinfo->is_italic();
    BLOB_CHOICE *choice = word.GetBlobChoice(i);
    if (choice && fontinfo_table.size() > 0) {
      // Get better information from the specific choice, if available.
      int font_id1 = choice->fontinfo_id();
      bool font1_is_italic = font_id1 >= 0 ? fontinfo_table.at(font_id1).is_italic() : false;
      int font_id2 = choice->fontinfo_id2();
      is_italic = font1_is_italic && (font_id2 < 0 || fontinfo_table.at(font_id2).is_italic());
    }
 
    float height_fraction = 1.0f;
    float char_height = blob->bounding_box().height();
    float normal_height = char_height;
    if (wc.unicharset()->top_bottom_useful()) {
      int min_bot, max_bot, min_top, max_top;
      wc.unicharset()->get_top_bottom(unichar_id, &min_bot, &max_bot, &min_top, &max_top);
      float hi_height = max_top - max_bot;
      float lo_height = min_top - min_bot;
      normal_height = (hi_height + lo_height) / 2;
      if (normal_height >= kBlnXHeight) {
        // Only ding characters that we have decent information for because
        // they're supposed to be normal sized, not tiny specks or dashes.
        height_fraction = char_height / normal_height;
      }
    }
    bool bad_height = height_fraction < superscript_scaledown_ratio;
 
    if (debug) {
      if (is_italic) {
        tprintf(" Rejecting: superscript is italic.\n");
      }
      if (is_punc) {
        tprintf(" Rejecting: punctuation present.\n");
      }
      const char *char_str = wc.unicharset()->id_to_unichar(unichar_id);
      if (bad_certainty) {
        tprintf(
            " Rejecting: don't believe character %s with certainty %.2f "
            "which is less than threshold %.2f\n",
            char_str, char_certainty, certainty_threshold);
      }
      if (bad_height) {
        tprintf(
            " Rejecting: character %s seems too small @ %.2f versus "
            "expected %.2f\n",
            char_str, char_height, normal_height);
      }
    }
    if (bad_certainty || bad_height || is_punc || is_italic) {
      if (ok_run_count == i) {
        initial_ok_run_count = ok_run_count;
      }
      ok_run_count = 0;
    } else {
      ok_run_count++;
    }
    if (char_certainty < worst_certainty) {
      worst_certainty = char_certainty;
    }
  }
  bool all_ok = ok_run_count == wc.length();
  if (all_ok && debug) {
    tprintf(" Accept: worst revised certainty is %.2f\n", worst_certainty);
  }
  if (!all_ok) {
    if (left_ok) {
      *left_ok = initial_ok_run_count;
    }
    if (right_ok) {
      *right_ok = ok_run_count;
    }
  }
  return all_ok;
}
 
} // namespace tesseract