tesseract/textord/blkocc.cpp

/*****************************************************************************
 *
 * File:        blkocc.cpp  (Formerly blockocc.c)
 * Description:  Block Occupancy routines
 * Author:       Chris Newton
 * Created:      Fri Nov 8
 * Modified:
 * Language:     C++
 * Package:      N/A
 * Status:       Experimental (Do Not Distribute)
 *
 * (c) Copyright 1991, Hewlett-Packard Company.
 ** 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.
 *
 ******************************************************************************/

/*
----------------------------------------------------------------------
              I n c l u d e s
----------------------------------------------------------------------
*/

#include <ctype.h>
#include <math.h>
#include "errcode.h"
#include "drawtord.h"
#include "blkocc.h"
#include "helpers.h"

double_VAR(textord_underline_threshold, 0.5, "Fraction of width occupied");

// Forward declarations of static functions
static void horizontal_cblob_projection(C_BLOB *blob,   // blob to project
                                        STATS *stats);  // output
static void horizontal_coutline_projection(C_OUTLINE *outline,
                                           STATS *stats);        // output

/**
 * test_underline
 *
 * Check to see if the blob is an underline.
 * Return TRUE if it is.
 */

BOOL8 test_underline(                   //look for underlines
                     BOOL8 testing_on,  //< drawing blob
                     C_BLOB *blob,      //< blob to test
                     inT16 baseline,    //< coords of baseline
                     inT16 xheight      //< height of line
                    ) {
  inT16 occ;
  inT16 blob_width;              //width of blob
  TBOX blob_box;                  //bounding box
  inT32 desc_occ;
  inT32 x_occ;
  inT32 asc_occ;
  STATS projection;

  blob_box = blob->bounding_box ();
  blob_width = blob->bounding_box ().width ();
  projection.set_range (blob_box.bottom (), blob_box.top () + 1);
  if (testing_on) {
    //              blob->plot(to_win,GOLDENROD,GOLDENROD);
    //              line_color_index(to_win,GOLDENROD);
    //              move2d(to_win,blob_box.left(),baseline);
    //              draw2d(to_win,blob_box.right(),baseline);
    //              move2d(to_win,blob_box.left(),baseline+xheight);
    //              draw2d(to_win,blob_box.right(),baseline+xheight);
    tprintf
      ("Testing underline on blob at (%d,%d)->(%d,%d), base=%d\nOccs:",
      blob->bounding_box ().left (), blob->bounding_box ().bottom (),
      blob->bounding_box ().right (), blob->bounding_box ().top (),
      baseline);
  }
  horizontal_cblob_projection(blob, &projection);
  desc_occ = 0;
  for (occ = blob_box.bottom (); occ < baseline; occ++)
    if (occ <= blob_box.top () && projection.pile_count (occ) > desc_occ)
                                 //max in region
      desc_occ = projection.pile_count (occ);
  x_occ = 0;
  for (occ = baseline; occ <= baseline + xheight; occ++)
    if (occ >= blob_box.bottom () && occ <= blob_box.top ()
    && projection.pile_count (occ) > x_occ)
                                 //max in region
      x_occ = projection.pile_count (occ);
  asc_occ = 0;
  for (occ = baseline + xheight + 1; occ <= blob_box.top (); occ++)
    if (occ >= blob_box.bottom () && projection.pile_count (occ) > asc_occ)
      asc_occ = projection.pile_count (occ);
  if (testing_on) {
    tprintf ("%d %d %d\n", desc_occ, x_occ, asc_occ);
  }
  if (desc_occ == 0 && x_occ == 0 && asc_occ == 0) {
    tprintf ("Bottom=%d, top=%d, base=%d, x=%d\n",
      blob_box.bottom (), blob_box.top (), baseline, xheight);
    projection.print();
  }
  if (desc_occ > x_occ + x_occ
    && desc_occ > blob_width * textord_underline_threshold)
    return TRUE;                 //real underline
  if (asc_occ > x_occ + x_occ
    && asc_occ > blob_width * textord_underline_threshold)
    return TRUE;                 //overline
  return FALSE;                  //neither
}


/**
 * horizontal_cblob_projection
 *
 * Compute the horizontal projection of a cblob from its outlines
 * and add to the given STATS.
 */

static void horizontal_cblob_projection(               //project outlines
                                 C_BLOB *blob,  //< blob to project
                                 STATS *stats   //< output
                                ) {
                                 //outlines of blob
  C_OUTLINE_IT out_it = blob->out_list ();

  for (out_it.mark_cycle_pt (); !out_it.cycled_list (); out_it.forward ()) {
    horizontal_coutline_projection (out_it.data (), stats);
  }
}


/**
 * horizontal_coutline_projection
 *
 * Compute the horizontal projection of a outline from its outlines
 * and add to the given STATS.
 */

static void horizontal_coutline_projection(                     //project outlines
                                    C_OUTLINE *outline,  //< outline to project
                                    STATS *stats         //< output
                                   ) {
  ICOORD pos;                    //current point
  ICOORD step;                   //edge step
  inT32 length;                  //of outline
  inT16 stepindex;               //current step
  C_OUTLINE_IT out_it = outline->child ();

  pos = outline->start_pos ();
  length = outline->pathlength ();
  for (stepindex = 0; stepindex < length; stepindex++) {
    step = outline->step (stepindex);
    if (step.y () > 0) {
      stats->add (pos.y (), pos.x ());
    }
    else if (step.y () < 0) {
      stats->add (pos.y () - 1, -pos.x ());
    }
    pos += step;
  }

  for (out_it.mark_cycle_pt (); !out_it.cycled_list (); out_it.forward ()) {
    horizontal_coutline_projection (out_it.data (), stats);
  }
}