tesseract::AssociateUtils Class Reference

#include <associate.h>

Static Public Member Functions
static float	ComputeOutlineLength (float rating_cert_scale, const BLOB_CHOICE &b)
static float	ComputeRating (float rating_cert_scale, float cert, int width)
static void	ComputeStats (int col, int row, const AssociateStats *parent_stats, int parent_path_length, bool fixed_pitch, float max_char_wh_ratio, WERD_RES *word_res, bool debug, AssociateStats *stats)
static float	FixedPitchWidthCost (float norm_width, float right_gap, bool end_pos, float max_char_wh_ratio)
static float	FixedPitchGapCost (float norm_gap, bool end_pos)

Static Public Attributes
static const float	kMaxFixedPitchCharAspectRatio = 2.0f
static const float	kMinGap = 0.03f

Detailed Description

Definition at line 67 of file associate.h.

Member Function Documentation

ComputeOutlineLength()

static float tesseract::AssociateUtils::ComputeOutlineLength ( float  rating_cert_scale, const BLOB_CHOICE &  b  )

inlinestatic

Definition at line 80 of file associate.h.

                                                                 {
    return rating_cert_scale * b.rating() / b.certainty();
  }

ComputeRating()

static float tesseract::AssociateUtils::ComputeRating ( float  rating_cert_scale, float  cert, int  width  )

inlinestatic

Definition at line 84 of file associate.h.

                                                           {
    return static_cast<float>(width) * cert / rating_cert_scale;
  }

ComputeStats()

void tesseract::AssociateUtils::ComputeStats ( int  col, int  row, const AssociateStats *  parent_stats, int  parent_path_length, bool  fixed_pitch, float  max_char_wh_ratio, WERD_RES *  word_res, bool  debug, AssociateStats *  stats  )

static

Definition at line 37 of file associate.cpp.

                                                         {
  stats->Clear();

  ASSERT_HOST(word_res != NULL);
  if (word_res->blob_widths.empty()) {
    return;
  }
  if (debug) {
    tprintf("AssociateUtils::ComputeStats() for col=%d, row=%d%s\n",
            col, row, fixed_pitch ? " (fixed pitch)" : "");
  }
  float normalizing_height = kBlnXHeight;
  ROW* blob_row = word_res->blob_row;
  // TODO(rays/daria) Can unicharset.script_has_xheight be useful here?
  if (fixed_pitch && blob_row != NULL) {
    // For fixed pitch language like CJK, we use the full text height
    // as the normalizing factor so we are not dependent on xheight
    // calculation.
    if (blob_row->body_size() > 0.0f) {
      normalizing_height = word_res->denorm.y_scale() * blob_row->body_size();
    } else {
      normalizing_height = word_res->denorm.y_scale() *
          (blob_row->x_height() + blob_row->ascenders());
    }
    if (debug) {
      tprintf("normalizing height = %g (scale %g xheight %g ascenders %g)\n",
              normalizing_height, word_res->denorm.y_scale(),
              blob_row->x_height(), blob_row->ascenders());
    }
  }
  float wh_ratio = word_res->GetBlobsWidth(col, row) / normalizing_height;
  if (wh_ratio > max_char_wh_ratio) stats->bad_shape = true;
  // Compute the gap sum for this shape. If there are only negative or only
  // positive gaps, record their sum in stats->gap_sum. However, if there is
  // a mixture, record only the sum of the positive gaps.
  // TODO(antonova): explain fragment.
  int negative_gap_sum = 0;
  for (int c = col; c < row; ++c) {
    int gap = word_res->GetBlobsGap(c);
    (gap > 0) ? stats->gap_sum += gap : negative_gap_sum += gap;
  }
  if (stats->gap_sum == 0) stats->gap_sum = negative_gap_sum;
  if (debug) {
    tprintf("wh_ratio=%g (max_char_wh_ratio=%g) gap_sum=%d %s\n",
            wh_ratio, max_char_wh_ratio, stats->gap_sum,
            stats->bad_shape ? "bad_shape" : "");
  }
  // Compute shape_cost (for fixed pitch mode).
  if (fixed_pitch) {
    bool end_row = (row == (word_res->ratings->dimension() - 1));

    // Ensure that the blob has gaps on the left and the right sides
    // (except for beginning and ending punctuation) and that there is
    // no cutting through ink at the blob boundaries.
    if (col > 0) {
      float left_gap = word_res->GetBlobsGap(col - 1) / normalizing_height;
      SEAM *left_seam = word_res->seam_array[col - 1];
      if ((!end_row && left_gap < kMinGap) || left_seam->priority() > 0.0f) {
        stats->bad_shape = true;
      }
      if (debug) {
        tprintf("left_gap %g, left_seam %g %s\n", left_gap,
                left_seam->priority(), stats->bad_shape ? "bad_shape" : "");
      }
    }
    float right_gap = 0.0f;
    if (!end_row) {
      right_gap = word_res->GetBlobsGap(row) / normalizing_height;
      SEAM *right_seam = word_res->seam_array[row];
      if (right_gap < kMinGap || right_seam->priority() > 0.0f) {
        stats->bad_shape = true;
        if (right_gap < kMinGap) stats->bad_fixed_pitch_right_gap = true;
      }
      if (debug) {
        tprintf("right_gap %g right_seam %g %s\n", right_gap,
                right_seam->priority(), stats->bad_shape ? "bad_shape" : "");
      }
    }

    // Impose additional segmentation penalties if blob widths or gaps
    // distribution don't fit a fixed-pitch model.
    // Since we only know the widths and gaps of the path explored so far,
    // the means and variances are computed for the path so far (not
    // considering characters to the right of the last character on the path).
    stats->full_wh_ratio = wh_ratio + right_gap;
    if (parent_stats != NULL) {
      stats->full_wh_ratio_total =
        (parent_stats->full_wh_ratio_total + stats->full_wh_ratio);
      float mean =
        stats->full_wh_ratio_total / static_cast<float>(parent_path_length+1);
      stats->full_wh_ratio_var =
        parent_stats->full_wh_ratio_var + pow(mean-stats->full_wh_ratio, 2);
    } else {
      stats->full_wh_ratio_total = stats->full_wh_ratio;
    }
    if (debug) {
      tprintf("full_wh_ratio %g full_wh_ratio_total %g full_wh_ratio_var %g\n",
              stats->full_wh_ratio, stats->full_wh_ratio_total,
              stats->full_wh_ratio_var);
    }

    stats->shape_cost =
      FixedPitchWidthCost(wh_ratio, right_gap, end_row, max_char_wh_ratio);

    // For some reason Tesseract prefers to treat the whole CJ words
    // as one blob when the initial segmentation is particularly bad.
    // This hack is to avoid favoring such states.
    if (col == 0 && end_row && wh_ratio > max_char_wh_ratio) {
      stats->shape_cost += 10;
    }
    stats->shape_cost += stats->full_wh_ratio_var;
    if (debug) tprintf("shape_cost %g\n", stats->shape_cost);
  }
}

FixedPitchGapCost()

static float tesseract::AssociateUtils::FixedPitchGapCost ( float  norm_gap, bool  end_pos  )

inlinestatic

Definition at line 116 of file associate.h.

                                                                      {
    return (norm_gap < 0.05 && !end_pos) ? 5.0f : 0.0f;
  }

FixedPitchWidthCost()

float tesseract::AssociateUtils::FixedPitchWidthCost ( float  norm_width, float  right_gap, bool  end_pos, float  max_char_wh_ratio  )

static

Definition at line 159 of file associate.cpp.

                                                                   {
  float cost = 0.0f;
  if (norm_width > max_char_wh_ratio) cost += norm_width;
  if (norm_width > kMaxFixedPitchCharAspectRatio)
    cost += norm_width * norm_width;  // extra penalty for merging CJK chars
  // Penalize skinny blobs, except for punctuation in the last position.
  if (norm_width+right_gap < 0.5f && !end_pos) {
    cost += 1.0f - (norm_width + right_gap);
  }
  return cost;
}

Member Data Documentation

kMaxFixedPitchCharAspectRatio

const float tesseract::AssociateUtils::kMaxFixedPitchCharAspectRatio = 2.0f

static

Definition at line 69 of file associate.h.

kMinGap

const float tesseract::AssociateUtils::kMinGap = 0.03f

static

Definition at line 70 of file associate.h.

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The documentation for this class was generated from the following files:

• /home/stefan/src/github/tesseract-ocr/tesseract/wordrec/associate.h
• /home/stefan/src/github/tesseract-ocr/tesseract/wordrec/associate.cpp