Method IdentifySpecialText

deps/tesseract/ccmain/equationdetect.cpp:157–229

}

void EquationDetect::IdentifySpecialText(
    BLOBNBOX *blobnbox, const int height_th) {
  ASSERT_HOST(blobnbox != NULL);
  if (blobnbox->bounding_box().height() < height_th && height_th > 0) {
    // For small blob, we simply set to BSTT_NONE.
    blobnbox->set_special_text_type(BSTT_NONE);
    return;
  }

  BLOB_CHOICE_LIST ratings_equ, ratings_lang;
  C_BLOB* blob = blobnbox->cblob();
  // TODO(joeliu/rays) Fix this. We may have to normalize separately for
  // each classifier here, as they may require different PolygonalCopy.
  TBLOB* tblob = TBLOB::PolygonalCopy(false, blob);
  const TBOX& box = tblob->bounding_box();

  // Normalize the blob. Set the origin to the place we want to be the
  // bottom-middle, and scaling is to make the height the x-height.
  float scaling = static_cast<float>(kBlnXHeight) / box.height();
  float x_orig = (box.left() + box.right()) / 2.0f, y_orig = box.bottom();
  TBLOB* normed_blob = new TBLOB(*tblob);
  normed_blob->Normalize(NULL, NULL, NULL, x_orig, y_orig, scaling, scaling,
                         0.0f, static_cast<float>(kBlnBaselineOffset),
                         false, NULL);
  equ_tesseract_.AdaptiveClassifier(normed_blob, &ratings_equ);
  lang_tesseract_->AdaptiveClassifier(normed_blob, &ratings_lang);
  delete normed_blob;
  delete tblob;

  // Get the best choice from ratings_lang and rating_equ. As the choice in the
  // list has already been sorted by the certainty, we simply use the first
  // choice.
  BLOB_CHOICE *lang_choice = NULL, *equ_choice = NULL;
  if (ratings_lang.length() > 0) {
    BLOB_CHOICE_IT choice_it(&ratings_lang);
    lang_choice = choice_it.data();
  }
  if (ratings_equ.length() > 0) {
    BLOB_CHOICE_IT choice_it(&ratings_equ);
    equ_choice = choice_it.data();
  }

  float lang_score = lang_choice ? lang_choice->certainty() : -FLT_MAX;
  float equ_score = equ_choice ? equ_choice->certainty() : -FLT_MAX;

  const float kConfScoreTh = -5.0f, kConfDiffTh = 1.8;
  // The scores here are negative, so the max/min == fabs(min/max).
  // float ratio = fmax(lang_score, equ_score) / fmin(lang_score, equ_score);
  float diff = fabs(lang_score - equ_score);
  BlobSpecialTextType type = BSTT_NONE;

  // Classification.
  if (fmax(lang_score, equ_score) < kConfScoreTh) {
    // If both score are very small, then mark it as unclear.
    type = BSTT_UNCLEAR;
  } else if (diff > kConfDiffTh && equ_score > lang_score) {
    // If equ_score is significantly higher, then we classify this character as
    // math symbol.