Tesseract  3.02
Static Public Member Functions | Static Public Attributes
tesseract::AssociateUtils Class Reference

#include <associate.h>

List of all members.

Static Public Member Functions

static void ComputeStats (int col, int row, const AssociateStats *parent_stats, int parent_path_length, bool fixed_pitch, float max_char_wh_ratio, const DENORM *denorm, CHUNKS_RECORD *chunks_record, int debug_level, AssociateStats *stats)
static int GetChunksWidth (WIDTH_RECORD *width_record, int start_blob, int last_blob)
static int GetChunksGap (WIDTH_RECORD *width_record, int last_chunk)
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 96 of file associate.h.

Member Function Documentation

void tesseract::AssociateUtils::ComputeStats ( int  col,
int  row,
const AssociateStats *  parent_stats,
int  parent_path_length,
bool  fixed_pitch,
float  max_char_wh_ratio,
const DENORM *  denorm,
CHUNKS_RECORD *  chunks_record,
int  debug_level,
AssociateStats *  stats 
) [static]

Definition at line 37 of file associate.cpp.

                                                         {
  stats->Clear();

  if (debug_level > 0) {
    tprintf("AssociateUtils::ComputeStats() for col=%d, row=%d%s\n",
            col, row, fixed_pitch ? " (fixed pitch)" : "");
  }
  float normalizing_height = BASELINE_SCALE;
  // TODO(rays/daria) Can unicharset.script_has_xheight be useful here?
  if (fixed_pitch && denorm != NULL && denorm->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 (denorm->row()->body_size() > 0.0f) {
      normalizing_height = denorm->y_scale() * denorm->row()->body_size();
    } else {
      normalizing_height = denorm->y_scale() *
          (denorm->row()->x_height() + denorm->row()->ascenders());
    }
    if (debug_level > 0) {
      tprintf("normalizing height = %g (scale %g xheight %g ascenders %g)\n",
              normalizing_height, denorm->y_scale(), denorm->row()->x_height(),
              denorm->row()->ascenders());
    }
  }
  float wh_ratio =
    GetChunksWidth(chunks_record->chunk_widths, col, row) / normalizing_height;
  if (debug_level) tprintf("wh_ratio %g\n", wh_ratio);
  if (wh_ratio > max_char_wh_ratio) stats->bad_shape = true;
  if (fixed_pitch) {
    bool end_row = (row == (chunks_record->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 =
        GetChunksGap(chunks_record->chunk_widths, col-1) / normalizing_height;
      SEAM *left_seam =
        static_cast<SEAM *>(array_value(chunks_record->splits, col-1));
      if (debug_level) {
        tprintf("left_gap %g, left_seam %g\n", left_gap, left_seam->priority);
      }
      if ((!end_row && left_gap < kMinGap) || left_seam->priority > 0.0f) {
        stats->bad_shape = true;
      }
    }
    float right_gap = 0.0f;
    if (!end_row) {
      right_gap =
        GetChunksGap(chunks_record->chunk_widths, row) / normalizing_height;
      SEAM *right_seam =
        static_cast<SEAM *>(array_value(chunks_record->splits, row));
      if (debug_level) {
        tprintf("right_gap %g right_seam %g\n",
                right_gap, right_seam->priority);
      }
      if (right_gap < kMinGap || right_seam->priority > 0.0f) {
        stats->bad_shape = true;
        if (right_gap < kMinGap) stats->bad_fixed_pitch_right_gap = true;
      }
    }

    // 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_level) {
      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_level) tprintf("shape_cost %g\n", stats->shape_cost);
  }
}
static float tesseract::AssociateUtils::FixedPitchGapCost ( float  norm_gap,
bool  end_pos 
) [inline, static]

Definition at line 143 of file associate.h.

                                                                      {
    return (norm_gap < 0.05 && !end_pos) ? 5.0f : 0.0f;
  }
float tesseract::AssociateUtils::FixedPitchWidthCost ( float  norm_width,
float  right_gap,
bool  end_pos,
float  max_char_wh_ratio 
) [static]

Definition at line 152 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;
}
static int tesseract::AssociateUtils::GetChunksGap ( WIDTH_RECORD *  width_record,
int  last_chunk 
) [inline, static]

Definition at line 132 of file associate.h.

                                                                             {
    return (last_chunk >= 0 && last_chunk < width_record->num_chars - 1) ?
      width_record->widths[last_chunk * 2 + 1] : 0;
  }
int tesseract::AssociateUtils::GetChunksWidth ( WIDTH_RECORD *  width_record,
int  start_blob,
int  last_blob 
) [static]

Definition at line 144 of file associate.cpp.

                                                                  {
  int result = 0;
  for (int x = start_blob * 2; x <= last_blob * 2; x++)
    result += width_record->widths[x];
  return result;
}

Member Data Documentation

const float tesseract::AssociateUtils::kMaxFixedPitchCharAspectRatio = 2.0f [static]

Definition at line 98 of file associate.h.

const float tesseract::AssociateUtils::kMinGap = 0.03f [static]

Definition at line 99 of file associate.h.

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