tesseract/wordrec/associate.h

///////////////////////////////////////////////////////////////////////
// File:        associate.h
// Description: Structs, classes, typedefs useful for the segmentation
//              search. Functions for scoring segmentation paths according
//              to their character widths, gap widths and seam cuts.
// Author:      Daria Antonova
// Created:     Mon Mar 8 11:26:43 PDT 2010
//
// (C) Copyright 2010, 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 ASSOCIATE_H
#define ASSOCIATE_H

#include "blobs.h"
#include "elst.h"
#include "matrix.h"
#include "seam.h"
#include "split.h"
#include "states.h"

typedef inT16 BLOB_WEIGHTS[MAX_NUM_CHUNKS];

// Each unichar evaluated.
struct EVALUATION_RECORD {
  float match;
  float certainty;
  char character;
  int width;
  int gap;
};

typedef EVALUATION_RECORD EVALUATION_ARRAY[MAX_NUM_CHUNKS];

// Classification info for chunks.
//
// TODO(daria): move to tesseract namespace when obsolete code using
// this struct that is not in tesseract namespace is deprecated.
struct CHUNKS_RECORD {
  MATRIX *ratings;
  TBLOB *chunks;
  SEAMS splits;
  int x_height;
  WIDTH_RECORD *chunk_widths;
  WIDTH_RECORD *char_widths;
  inT16 *weights;
};

namespace tesseract {

// Statisitcs about character widths, gaps and seams.
struct AssociateStats {
  AssociateStats() { Clear(); }

  void Clear() {
    shape_cost = 0.0f;
    bad_shape = false;
    full_wh_ratio = 0.0f;
    full_wh_ratio_total = 0.0f;
    full_wh_ratio_var = 0.0f;
    bad_fixed_pitch_right_gap = false;
    bad_fixed_pitch_wh_ratio = false;
  }

  void Print() {
    tprintf("AssociateStats: w(%g %d) s(%g %d)\n", shape_cost, bad_shape);
  }

  float shape_cost;           // cost of blob shape
  bool bad_shape;             // true if the shape of the blob is unacceptable
  float full_wh_ratio;        // width-to-hight ratio + gap on the right
  float full_wh_ratio_total;  // sum of width-to-hight ratios
                              // on the path terminating at this blob
  float full_wh_ratio_var;    // variance of full_wh_ratios on the path
  bool bad_fixed_pitch_right_gap;  // true if there is no gap before
                                   // the blob on the right
  bool bad_fixed_pitch_wh_ratio;   // true if the blobs has width-to-hight
                                   // ratio > kMaxFixedPitchCharAspectRatio
};

// Utility functions for scoring segmentation paths according to their
// character widths, gap widths, seam characteristics.
class AssociateUtils {
 public:
  static const float kMaxFixedPitchCharAspectRatio;
  static const float kMinGap;

  // Computes character widths, gaps and seams stats given the
  // AssociateStats of the path so far, col, row of the blob that
  // is being added to the path, and CHUNKS_RECORD containing information
  // about character widths, gaps and seams.
  // Fills associate_cost with the combined shape, gap and seam cost
  // of adding a unichar from (col, row) to the path (note that since
  // this function could be used to compute the prioritization for
  // pain points, (col, row) entry might not be classified yet; thus
  // information in the (col, row) entry of the ratings matrix is not used).
  //
  // Note: the function assumes that chunks_record, stats and
  // associate_cost pointers are not NULL.
  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);

  // Returns the width of a chunk which is a composed of several blobs
  // blobs[start_blob..last_blob] inclusively.
  // Widths/gaps records are in the form:
  // width_record->num_char = n
  // width_record->widths[2*n-1] = w0,g0,w1,g1..w(n-1),g(n-1)
  static int GetChunksWidth(WIDTH_RECORD *width_record,
                            int start_blob, int last_blob);

  // Returns the width of a gap between the specified chunk and the next one.
  static inline int GetChunksGap(WIDTH_RECORD *width_record, int last_chunk) {
    return (last_chunk >= 0 && last_chunk < width_record->num_chars - 1) ?
      width_record->widths[last_chunk * 2 + 1] : 0;
  }

  // Returns the width cost for fixed-pitch text.
  static float FixedPitchWidthCost(float norm_width, float right_gap,
                                   bool end_pos, float max_char_wh_ratio);

  // Returns the gap cost for fixed-pitch text (penalizes vertically
  // overlapping components).
  static inline float FixedPitchGapCost(float norm_gap, bool end_pos) {
    return (norm_gap < 0.05 && !end_pos) ? 5.0f : 0.0f;
  }
};

}  // namespace tesseract

#endif