alignedblob.h

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// File:        alignedblob.h
// Description: A class to find vertically aligned blobs in a BBGrid,
//              and a struct to hold control parameters.
// Author:      Ray Smith
//
// (C) Copyright 2008, 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 TESSERACT_TEXTORD_ALIGNEDBLOB_H_
#define TESSERACT_TEXTORD_ALIGNEDBLOB_H_
 
#include "bbgrid.h"
#include "blobbox.h"
#include "tabvector.h"
 
namespace tesseract {
 
extern INT_VAR_H(textord_debug_bugs);
extern INT_VAR_H(textord_debug_tabfind);
extern BOOL_VAR_H(textord_debug_printable);
 
// Simple structure to hold the search parameters for AlignedBlob.
// The members are mostly derived from constants, which are
// conditioned on the alignment parameter.
// For finding vertical lines, a different set of constants are
// used, conditioned on the different constructor.
struct AlignedBlobParams {
  // Constructor to set the parameters for finding aligned and ragged tabs.
  // Vertical_x and vertical_y are the current estimates of the true vertical
  // direction (up) in the image. Height is the height of the starter blob.
  // v_gap_multiple is the multiple of height that will be used as a limit
  // on vertical gap before giving up and calling the line ended.
  // resolution is the original image resolution, and align0 indicates the
  // type of tab stop to be found.
  AlignedBlobParams(int vertical_x, int vertical_y, int height, int v_gap_multiple,
                    int min_gutter_width, int resolution, TabAlignment alignment0);
  // Constructor to set the parameters for finding vertical lines.
  // Vertical_x and vertical_y are the current estimates of the true vertical
  // direction (up) in the image. Width is the width of the starter blob.
  AlignedBlobParams(int vertical_x, int vertical_y, int width);
 
  // Fit the vertical vector into an ICOORD, which is 16 bit.
  void set_vertical(int vertical_x, int vertical_y);
 
  double gutter_fraction; // Multiple of height used for min_gutter.
  bool right_tab;         // We are looking at right edges.
  bool ragged;            // We are looking for a ragged (vs aligned) edge.
  TabAlignment alignment; // The type we are trying to produce.
  TabType confirmed_type; // Type to flag blobs if accepted.
  int max_v_gap;          // Max vertical gap to be tolerated.
  int min_gutter;         // Minimum gutter between columns.
  // Tolerances allowed on horizontal alignment of aligned edges.
  int l_align_tolerance; // Left edges.
  int r_align_tolerance; // Right edges.
  // Conditions for accepting a line.
  int min_points; // Minimum number of points to be OK.
  int min_length; // Min length of completed line.
 
  ICOORD vertical; // Current estimate of logical vertical.
};
 
// The AlignedBlob class contains code to find vertically aligned blobs.
// This is factored out into a separate class, so it can be used by both
// vertical line finding (LineFind) and tabstop finding (TabFind).
class TESS_API AlignedBlob : public BlobGrid {
public:
  AlignedBlob(int gridsize, const ICOORD &bleft, const ICOORD &tright);
  ~AlignedBlob() override;
 
  // Return true if the given coordinates are within the test rectangle
  // and the debug level is at least the given detail level.
  static bool WithinTestRegion(int detail_level, int x, int y);
 
  // Display the tab codes of the BLOBNBOXes in this grid.
  ScrollView *DisplayTabs(const char *window_name, ScrollView *tab_win);
 
  // Finds a vector corresponding to a set of vertically aligned blob edges
  // running through the given box. The type of vector returned and the
  // search parameters are determined by the AlignedBlobParams.
  // vertical_x and y are updated with an estimate of the real
  // vertical direction. (skew finding.)
  // Returns nullptr if no decent vector can be found.
  TabVector *FindVerticalAlignment(AlignedBlobParams align_params, BLOBNBOX *bbox, int *vertical_x,
                                   int *vertical_y);
 
private:
  // Find a set of blobs that are aligned in the given vertical
  // direction with the given blob. Returns a list of aligned
  // blobs and the number in the list.
  // For other parameters see FindAlignedBlob below.
  int AlignTabs(const AlignedBlobParams &params, bool top_to_bottom, BLOBNBOX *bbox,
                BLOBNBOX_CLIST *good_points, int *end_y);
 
  // Search vertically for a blob that is aligned with the input bbox.
  // The search parameters are determined by AlignedBlobParams.
  // top_to_bottom tells whether to search down or up.
  // The return value is nullptr if nothing was found in the search box
  // or if a blob was found in the gutter. On a nullptr return, end_y
  // is set to the edge of the search box or the leading edge of the
  // gutter blob if one was found.
  BLOBNBOX *FindAlignedBlob(const AlignedBlobParams &p, bool top_to_bottom, BLOBNBOX *bbox,
                            int x_start, int *end_y);
};
 
} // namespace tesseract.
 
#endif // TESSERACT_TEXTORD_ALIGNEDBLOB_H_