src/textord/pitsync1.cpp

/**********************************************************************
 * File:        pitsync1.cpp  (Formerly pitsync.c)
 * Description: Code to find the optimum fixed pitch segmentation of some blobs.
 * Author:      Ray Smith
 *
 * (C) Copyright 1992, Hewlett-Packard Ltd.
 ** 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 "pitsync1.h"

#include <cfloat> // for FLT_MAX
#include <cmath>

namespace tesseract {

INT_VAR(pitsync_linear_version, 6, "Use new fast algorithm");
double_VAR(pitsync_joined_edge, 0.75, "Dist inside big blob for chopping");
double_VAR(pitsync_offset_freecut_fraction, 0.25, "Fraction of cut for free cuts");

/**********************************************************************
 * FPSEGPT::FPSEGPT
 *
 * Constructor to make a new FPSEGPT.
 * The existing FPCUTPT is duplicated.
 **********************************************************************/

FPSEGPT::FPSEGPT(  // constructor
    FPCUTPT *cutpt // create from new form
) {
  pred = nullptr;
  mean_sum = cutpt->sum();
  sq_sum = cutpt->squares();
  cost = cutpt->cost_function();
  faked = cutpt->faked;
  terminal = cutpt->terminal;
  fake_count = cutpt->fake_count;
  xpos = cutpt->position();
  mid_cuts = cutpt->cheap_cuts();
}

/**********************************************************************
 * FPSEGPT::FPSEGPT
 *
 * Constructor to make a new FPSEGPT.
 **********************************************************************/

FPSEGPT::FPSEGPT( // constructor
    int16_t x     // position
    )
    : xpos(x) {
  pred = nullptr;
  mean_sum = 0;
  sq_sum = 0;
  cost = 0;
  faked = false;
  terminal = false;
  fake_count = 0;
  mid_cuts = 0;
}

/**********************************************************************
 * FPSEGPT::FPSEGPT
 *
 * Constructor to make a new FPSEGPT.
 **********************************************************************/

FPSEGPT::FPSEGPT(           // constructor
    int16_t x,              // position
    bool faking,            // faking this one
    int16_t offset,         // dist to gap
    int16_t region_index,   // segment number
    int16_t pitch,          // proposed pitch
    int16_t pitch_error,    // allowed tolerance
    FPSEGPT_LIST *prev_list // previous segment
    )
    : fake_count(0), xpos(x), mean_sum(0.0), sq_sum(0.0) {
  int16_t best_fake;              // on previous
  FPSEGPT *segpt;                 // segment point
  int32_t dist;                   // from prev segment
  double sq_dist;                 // squared distance
  double mean;                    // mean pitch
  double total;                   // total dists
  double factor;                  // cost function
  FPSEGPT_IT pred_it = prev_list; // for previuos segment

  cost = FLT_MAX;
  pred = nullptr;
  faked = faking;
  terminal = false;
  best_fake = INT16_MAX;
  mid_cuts = 0;
  for (pred_it.mark_cycle_pt(); !pred_it.cycled_list(); pred_it.forward()) {
    segpt = pred_it.data();
    if (segpt->fake_count < best_fake) {
      best_fake = segpt->fake_count;
    }
    dist = x - segpt->xpos;
    if (dist >= pitch - pitch_error && dist <= pitch + pitch_error && !segpt->terminal) {
      total = segpt->mean_sum + dist;
      sq_dist = dist * dist + segpt->sq_sum + offset * offset;
      // sum of squarees
      mean = total / region_index;
      factor = mean - pitch;
      factor *= factor;
      factor += sq_dist / (region_index)-mean * mean;
      if (factor < cost) {
        cost = factor; // find least cost
        pred = segpt;  // save path
        mean_sum = total;
        sq_sum = sq_dist;
        fake_count = segpt->fake_count + faked;
      }
    }
  }
  if (fake_count > best_fake + 1) {
    pred = nullptr; // fail it
  }
}

/**********************************************************************
 * check_pitch_sync
 *
 * Construct the lattice of possible segmentation points and choose the
 * optimal path. Return the optimal path only.
 * The return value is a measure of goodness of the sync.
 **********************************************************************/

double check_pitch_sync(   // find segmentation
    BLOBNBOX_IT *blob_it,  // blobs to do
    int16_t blob_count,    // no of blobs
    int16_t pitch,         // pitch estimate
    int16_t pitch_error,   // tolerance
    STATS *projection,     // vertical
    FPSEGPT_LIST *seg_list // output list
) {
  int16_t x;          // current coord
  int16_t min_index;  // blob number
  int16_t max_index;  // blob number
  int16_t left_edge;  // of word
  int16_t right_edge; // of word
  int16_t right_max;  // max allowed x
  int16_t min_x;      // in this region
  int16_t max_x;
  int16_t region_index;
  int16_t best_region_index = 0; // for best result
  int16_t offset;                // dist to legal area
  int16_t left_best_x;           // edge of good region
  int16_t right_best_x;          // right edge
  TBOX min_box;                  // bounding box
  TBOX max_box;                  // bounding box
  TBOX next_box;                 // box of next blob
  FPSEGPT *segpt;                // segment point
  FPSEGPT_LIST *segpts;          // points in a segment
  double best_cost;              // best path
  double mean_sum;               // computes result
  FPSEGPT *best_end;             // end of best path
  BLOBNBOX_IT min_it;            // copy iterator
  BLOBNBOX_IT max_it;            // copy iterator
  FPSEGPT_IT segpt_it;           // iterator
                                 // output segments
  FPSEGPT_IT outseg_it = seg_list;
  FPSEGPT_LIST_CLIST lattice; // list of lists
                              // region iterator
  FPSEGPT_LIST_C_IT lattice_it = &lattice;

  //      tprintf("Computing sync on word of %d blobs with pitch %d\n",
  //              blob_count, pitch);
  //      if (blob_count==8 && pitch==27)
  //              projection->print(stdout,true);
  if (pitch < 3) {
    pitch = 3; // nothing ludicrous
  }
  if ((pitch - 3) / 2 < pitch_error) {
    pitch_error = (pitch - 3) / 2;
  }
  min_it = *blob_it;
  min_box = box_next(&min_it); // get box
  //      if (blob_count==8 && pitch==27)
  //              tprintf("1st box at (%d,%d)->(%d,%d)\n",
  //                      min_box.left(),min_box.bottom(),
  //                      min_box.right(),min_box.top());
  // left of word
  left_edge = min_box.left() + pitch_error;
  for (min_index = 1; min_index < blob_count; min_index++) {
    min_box = box_next(&min_it);
    //              if (blob_count==8 && pitch==27)
    //                      tprintf("Box at (%d,%d)->(%d,%d)\n",
    //                              min_box.left(),min_box.bottom(),
    //                              min_box.right(),min_box.top());
  }
  right_edge = min_box.right(); // end of word
  max_x = left_edge;
  // min permissible
  min_x = max_x - pitch + pitch_error * 2 + 1;
  right_max = right_edge + pitch - pitch_error - 1;
  segpts = new FPSEGPT_LIST; // list of points
  segpt_it.set_to_list(segpts);
  for (x = min_x; x <= max_x; x++) {
    segpt = new FPSEGPT(x); // make a new one
                            // put in list
    segpt_it.add_after_then_move(segpt);
  }
  // first segment
  lattice_it.add_before_then_move(segpts);
  min_index = 0;
  region_index = 1;
  best_cost = FLT_MAX;
  best_end = nullptr;
  min_it = *blob_it;
  min_box = box_next(&min_it); // first box
  do {
    left_best_x = -1;
    right_best_x = -1;
    segpts = new FPSEGPT_LIST; // list of points
    segpt_it.set_to_list(segpts);
    min_x += pitch - pitch_error; // next limits
    max_x += pitch + pitch_error;
    while (min_box.right() < min_x && min_index < blob_count) {
      min_index++;
      min_box = box_next(&min_it);
    }
    max_it = min_it;
    max_index = min_index;
    max_box = min_box;
    next_box = box_next(&max_it);
    for (x = min_x; x <= max_x && x <= right_max; x++) {
      while (x < right_edge && max_index < blob_count && x > max_box.right()) {
        max_index++;
        max_box = next_box;
        next_box = box_next(&max_it);
      }
      if (x <= max_box.left() + pitch_error || x >= max_box.right() - pitch_error ||
          x >= right_edge || (max_index < blob_count - 1 && x >= next_box.left()) ||
          (x - max_box.left() > pitch * pitsync_joined_edge &&
           max_box.right() - x > pitch * pitsync_joined_edge)) {
        //                      || projection->local_min(x))
        if (x - max_box.left() > 0 && x - max_box.left() <= pitch_error) {
          // dist to real break
          offset = x - max_box.left();
        } else if (max_box.right() - x > 0 && max_box.right() - x <= pitch_error &&
                   (max_index >= blob_count - 1 || x < next_box.left())) {
          offset = max_box.right() - x;
        } else {
          offset = 0;
        }
        //                              offset=pitsync_offset_freecut_fraction*projection->pile_count(x);
        segpt = new FPSEGPT(x, false, offset, region_index, pitch, pitch_error, lattice_it.data());
      } else {
        offset = projection->pile_count(x);
        segpt = new FPSEGPT(x, true, offset, region_index, pitch, pitch_error, lattice_it.data());
      }
      if (segpt->previous() != nullptr) {
        segpt_it.add_after_then_move(segpt);
        if (x >= right_edge - pitch_error) {
          segpt->terminal = true; // no more wanted
          if (segpt->cost_function() < best_cost) {
            best_cost = segpt->cost_function();
            // find least
            best_end = segpt;
            best_region_index = region_index;
            left_best_x = x;
            right_best_x = x;
          } else if (segpt->cost_function() == best_cost && right_best_x == x - 1) {
            right_best_x = x;
          }
        }
      } else {
        delete segpt; // no good
      }
    }
    if (segpts->empty()) {
      if (best_end != nullptr) {
        break; // already found one
      }
      make_illegal_segment(lattice_it.data(), min_box, min_it, region_index, pitch, pitch_error,
                           segpts);
    } else {
      if (right_best_x > left_best_x + 1) {
        left_best_x = (left_best_x + right_best_x + 1) / 2;
        for (segpt_it.mark_cycle_pt();
             !segpt_it.cycled_list() && segpt_it.data()->position() != left_best_x;
             segpt_it.forward()) {
          ;
        }
        if (segpt_it.data()->position() == left_best_x) {
          // middle of region
          best_end = segpt_it.data();
        }
      }
    }
    // new segment
    lattice_it.add_before_then_move(segpts);
    region_index++;
  } while (min_x < right_edge);
  ASSERT_HOST(best_end != nullptr); // must always find some

  for (lattice_it.mark_cycle_pt(); !lattice_it.cycled_list(); lattice_it.forward()) {
    segpts = lattice_it.data();
    segpt_it.set_to_list(segpts);
    //              if (blob_count==8 && pitch==27)
    //              {
    //                      for
    //                      (segpt_it.mark_cycle_pt();!segpt_it.cycled_list();segpt_it.forward())
    //                      {
    //                              segpt=segpt_it.data();
    //                              tprintf("At %d, (%x) cost=%g, m=%g, sq=%g,
    //                              pred=%x\n",
    //                                      segpt->position(),segpt,segpt->cost_function(),
    //                                      segpt->sum(),segpt->squares(),segpt->previous());
    //                      }
    //                      tprintf("\n");
    //              }
    for (segpt_it.mark_cycle_pt(); !segpt_it.cycled_list() && segpt_it.data() != best_end;
         segpt_it.forward()) {
      ;
    }
    if (segpt_it.data() == best_end) {
      // save good one
      segpt = segpt_it.extract();
      outseg_it.add_before_then_move(segpt);
      best_end = segpt->previous();
    }
  }
  ASSERT_HOST(best_end == nullptr);
  ASSERT_HOST(!outseg_it.empty());
  outseg_it.move_to_last();
  mean_sum = outseg_it.data()->sum();
  mean_sum = mean_sum * mean_sum / best_region_index;
  if (outseg_it.data()->squares() - mean_sum < 0) {
    tprintf("Impossible sqsum=%g, mean=%g, total=%d\n", outseg_it.data()->squares(),
            outseg_it.data()->sum(), best_region_index);
  }
  lattice.deep_clear(); // shift the lot
  return outseg_it.data()->squares() - mean_sum;
}

/**********************************************************************
 * make_illegal_segment
 *
 * Make a fake set of chop points due to having no legal places.
 **********************************************************************/

void make_illegal_segment(   // find segmentation
    FPSEGPT_LIST *prev_list, // previous segments
    TBOX blob_box,           // bounding box
    BLOBNBOX_IT blob_it,     // iterator
    int16_t region_index,    // number of segment
    int16_t pitch,           // pitch estimate
    int16_t pitch_error,     // tolerance
    FPSEGPT_LIST *seg_list   // output list
) {
  int16_t x;         // current coord
  int16_t min_x = 0; // in this region
  int16_t max_x = 0;
  int16_t offset;                 // dist to edge
  FPSEGPT *segpt;                 // segment point
  FPSEGPT *prevpt;                // previous point
  float best_cost;                // best path
  FPSEGPT_IT segpt_it = seg_list; // iterator
                                  // previous points
  FPSEGPT_IT prevpt_it = prev_list;

  best_cost = FLT_MAX;
  for (prevpt_it.mark_cycle_pt(); !prevpt_it.cycled_list(); prevpt_it.forward()) {
    prevpt = prevpt_it.data();
    if (prevpt->cost_function() < best_cost) {
      // find least
      best_cost = prevpt->cost_function();
      min_x = prevpt->position();
      max_x = min_x; // limits on coords
    } else if (prevpt->cost_function() == best_cost) {
      max_x = prevpt->position();
    }
  }
  min_x += pitch - pitch_error;
  max_x += pitch + pitch_error;
  for (x = min_x; x <= max_x; x++) {
    while (x > blob_box.right()) {
      blob_box = box_next(&blob_it);
    }
    offset = x - blob_box.left();
    if (blob_box.right() - x < offset) {
      offset = blob_box.right() - x;
    }
    segpt = new FPSEGPT(x, false, offset, region_index, pitch, pitch_error, prev_list);
    if (segpt->previous() != nullptr) {
      ASSERT_HOST(offset >= 0);
      fprintf(stderr, "made fake at %d\n", x);
      // make one up
      segpt_it.add_after_then_move(segpt);
      segpt->faked = true;
      segpt->fake_count++;
    } else {
      delete segpt;
    }
  }
}

} // namespace tesseract