/**********************************************************************

 * File:        fixxht.cpp  (Formerly fixxht.c)

 * Description: Improve x_ht and look out for case inconsistencies

 * Author:      Phil Cheatle

 * Created:     Thu Aug  5 14:11:08 BST 1993

 *

 * (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 "float2int.h"

#include "params.h"

#include "tesseractclass.h"

#include <algorithm>

#include <cctype>

#include <cmath>

#include <cstring>

namespace tesseract {

// Fixxht overview.

// Premise: Initial estimate of x-height is adequate most of the time, but

// occasionally it is incorrect. Most notable causes of failure are:

// 1. Small caps, where the top of the caps is the same as the body text

// xheight. For small caps words the xheight needs to be reduced to correctly

// recognize the caps in the small caps word.

// 2. All xheight lines, such as summer. Here the initial estimate will have

// guessed that the blob tops are caps and will have placed the xheight too low.

// 3. Noise/logos beside words, or changes in font size on a line. Such

// things can blow the statistics and cause an incorrect estimate.

// 4. Incorrect baseline. Can happen when 2 columns are incorrectly merged.

// In this case the x-height is often still correct.

//

// Algorithm.

// Compare the vertical position (top only) of alphnumerics in a word with

// the range of positions in training data (in the unicharset).

// See CountMisfitTops. If any characters disagree sufficiently with the

// initial xheight estimate, then recalculate the xheight, re-run OCR on

// the word, and if the number of vertical misfits goes down, along with

// either the word rating or certainty, then keep the new xheight.

// The new xheight is calculated as follows:ComputeCompatibleXHeight

// For each alphanumeric character that has a vertically misplaced top

// (a misfit), yet its bottom is within the acceptable range (ie it is not

// likely a sub-or super-script) calculate the range of acceptable xheight

// positions from its range of tops, and give each value in the range a

// number of votes equal to the distance of its top from its acceptance range.

// The x-height position with the median of the votes becomes the new

// x-height. This assumes that most characters will be correctly recognized

// even if the x-height is incorrect. This is not a terrible assumption, but

// it is not great. An improvement would be to use a classifier that does

// not care about vertical position or scaling at all.

// Separately collect stats on shifted baselines and apply the same logic to

// computing a best-fit shift to fix the error. If the baseline needs to be

// shifted, but the x-height is OK, returns the original x-height along with

// the baseline shift to indicate that recognition needs to re-run.

// If the max-min top of a unicharset char is bigger than kMaxCharTopRange

// then the char top cannot be used to judge misfits or suggest a new top.

const int kMaxCharTopRange = 48;

// Returns the number of misfit blob tops in this word.

int Tesseract::CountMisfitTops(WERD_RES *word_res) {

  int bad_blobs = 0;

  int num_blobs = word_res->rebuild_word->NumBlobs();

  for (int blob_id = 0; blob_id < num_blobs; ++blob_id) {

    TBLOB *blob = word_res->rebuild_word->blobs[blob_id];

    UNICHAR_ID class_id = word_res->best_choice->unichar_id(blob_id);

    if (unicharset.get_isalpha(class_id) || unicharset.get_isdigit(class_id)) {

      int top = blob->bounding_box().top();

      if (top >= INT_FEAT_RANGE) {

        top = INT_FEAT_RANGE - 1;

      }

      int min_bottom, max_bottom, min_top, max_top;

      unicharset.get_top_bottom(class_id, &min_bottom, &max_bottom, &min_top, &max_top);

      if (max_top - min_top > kMaxCharTopRange) {

        continue;

      }

      bool bad =

          top < min_top - x_ht_acceptance_tolerance || top > max_top + x_ht_acceptance_tolerance;

      if (bad) {

        ++bad_blobs;

      }

      if (debug_x_ht_level >= 1) {

        tprintf("Class %s is %s with top %d vs limits of %d->%d, +/-%d\n",

                unicharset.id_to_unichar(class_id), bad ? "Misfit" : "OK", top, min_top, max_top,

                static_cast<int>(x_ht_acceptance_tolerance));

      }

    }

  }

  return bad_blobs;

}

// Returns a new x-height maximally compatible with the result in word_res.

// See comment above for overall algorithm.

float Tesseract::ComputeCompatibleXheight(WERD_RES *word_res, float *baseline_shift) {

  STATS top_stats(0, UINT8_MAX - 1);

  STATS shift_stats(-UINT8_MAX, UINT8_MAX - 1);

  int bottom_shift = 0;

  int num_blobs = word_res->rebuild_word->NumBlobs();

  do {

    top_stats.clear();

    shift_stats.clear();

    for (int blob_id = 0; blob_id < num_blobs; ++blob_id) {

      TBLOB *blob = word_res->rebuild_word->blobs[blob_id];

      UNICHAR_ID class_id = word_res->best_choice->unichar_id(blob_id);

      if (unicharset.get_isalpha(class_id) || unicharset.get_isdigit(class_id)) {

        int top = blob->bounding_box().top() + bottom_shift;

        // Clip the top to the limit of normalized feature space.

        if (top >= INT_FEAT_RANGE) {

          top = INT_FEAT_RANGE - 1;

        }

        int bottom = blob->bounding_box().bottom() + bottom_shift;

        int min_bottom, max_bottom, min_top, max_top;

        unicharset.get_top_bottom(class_id, &min_bottom, &max_bottom, &min_top, &max_top);

        // Chars with a wild top range would mess up the result so ignore them.

        if (max_top - min_top > kMaxCharTopRange) {

          continue;

        }

        int misfit_dist = std::max((min_top - x_ht_acceptance_tolerance) - top,

                                   top - (max_top + x_ht_acceptance_tolerance));

        int height = top - kBlnBaselineOffset;

        if (debug_x_ht_level >= 2) {

          tprintf("Class %s: height=%d, bottom=%d,%d top=%d,%d, actual=%d,%d: ",

                  unicharset.id_to_unichar(class_id), height, min_bottom, max_bottom, min_top,

                  max_top, bottom, top);

        }

        // Use only chars that fit in the expected bottom range, and where

        // the range of tops is sensibly near the xheight.

        if (min_bottom <= bottom + x_ht_acceptance_tolerance &&

            bottom - x_ht_acceptance_tolerance <= max_bottom && min_top > kBlnBaselineOffset &&

            max_top - kBlnBaselineOffset >= kBlnXHeight && misfit_dist > 0) {

          // Compute the x-height position using proportionality between the

          // actual height and expected height.

          int min_xht = DivRounded(height * kBlnXHeight, max_top - kBlnBaselineOffset);

          int max_xht = DivRounded(height * kBlnXHeight, min_top - kBlnBaselineOffset);

          if (debug_x_ht_level >= 2) {

            tprintf(" xht range min=%d, max=%d\n", min_xht, max_xht);

          }

          // The range of expected heights gets a vote equal to the distance

          // of the actual top from the expected top.

          for (int y = min_xht; y <= max_xht; ++y) {

            top_stats.add(y, misfit_dist);

          }

        } else if ((min_bottom > bottom + x_ht_acceptance_tolerance ||

                    bottom - x_ht_acceptance_tolerance > max_bottom) &&

                   bottom_shift == 0) {

          // Get the range of required bottom shift.

          int min_shift = min_bottom - bottom;

          int max_shift = max_bottom - bottom;

          if (debug_x_ht_level >= 2) {

            tprintf(" bottom shift min=%d, max=%d\n", min_shift, max_shift);

          }

          // The range of expected shifts gets a vote equal to the min distance

          // of the actual bottom from the expected bottom, spread over the

          // range of its acceptance.

          int misfit_weight = abs(min_shift);

          if (max_shift > min_shift) {

            misfit_weight /= max_shift - min_shift;

          }

          for (int y = min_shift; y <= max_shift; ++y) {

            shift_stats.add(y, misfit_weight);

          }

        } else {

          if (bottom_shift == 0) {

            // Things with bottoms that are already ok need to say so, on the

            // 1st iteration only.

            shift_stats.add(0, kBlnBaselineOffset);

          }

          if (debug_x_ht_level >= 2) {

            tprintf(" already OK\n");

          }

        }

      }

    }

    if (shift_stats.get_total() > top_stats.get_total()) {

      bottom_shift = IntCastRounded(shift_stats.median());

      if (debug_x_ht_level >= 2) {

        tprintf("Applying bottom shift=%d\n", bottom_shift);

      }

    }

  } while (bottom_shift != 0 && top_stats.get_total() < shift_stats.get_total());

  // Baseline shift is opposite sign to the bottom shift.

  *baseline_shift = -bottom_shift / word_res->denorm.y_scale();

  if (debug_x_ht_level >= 2) {

    tprintf("baseline shift=%g\n", *baseline_shift);

  }

  if (top_stats.get_total() == 0) {

    return bottom_shift != 0 ? word_res->x_height : 0.0f;

  }

  // The new xheight is just the median vote, which is then scaled out

  // of BLN space back to pixel space to get the x-height in pixel space.

  float new_xht = top_stats.median();

  if (debug_x_ht_level >= 2) {

    tprintf("Median xht=%f\n", new_xht);

    tprintf("Mode20:A: New x-height = %f (norm), %f (orig)\n", new_xht,

            new_xht / word_res->denorm.y_scale());

  }

  // The xheight must change by at least x_ht_min_change to be used.

  if (std::fabs(new_xht - kBlnXHeight) >= x_ht_min_change) {

    return new_xht / word_res->denorm.y_scale();

  } else {

    return bottom_shift != 0 ? word_res->x_height : 0.0f;

  }

}

} // namespace tesseract