tesseract/src/training/boxchar.h

/**********************************************************************
 * File:        boxchar.h
 * Description: Simple class to associate a Tesseract classification unit with
 *              its bounding box so that the boxes can be rotated as the image
 *              is rotated for degradation.  Also includes routines to output
 *              the character-tagged boxes to a boxfile.
 * Author:      Ray Smith
 * Created:     Mon Nov 18 2013
 *
 * (C) Copyright 2013, 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_TRAINING_BOXCHAR_H_
#define TESSERACT_TRAINING_BOXCHAR_H_

#include <string>
#include <vector>

#include "allheaders.h"  // from Leptonica
#include "platform.h"

struct Box;

namespace tesseract {

class BoxChar {
 public:
  BoxChar(const char* utf8_str, int len);

  ~BoxChar();

  // Accessors.
  const std::string& ch() const { return ch_; }
  const Box* box() const   { return box_; }
  const int& page() const  { return page_; }
  void set_rtl_index(int index) { rtl_index_ = index; }
  const int& rtl_index() const { return rtl_index_; }

  // Set the box_ member.
  void AddBox(int x, int y, int width, int height);

  void set_page(int page) { page_ = page; }

  std::string* mutable_ch() { return &ch_; }
  Box* mutable_box()   { return box_; }

  // Sort function for sorting by left edge of box. Note that this will not
  // work properly until after InsertNewlines and InsertSpaces.
  bool operator<(const BoxChar& other) const {
    if (box_ == nullptr) return true;
    if (other.box_ == nullptr) return false;
    return box_->x < other.box_->x;
  }
  // Increments *num_rtl and *num_ltr according to the directionality of
  // characters in the box.
  void GetDirection(int* num_rtl, int* num_ltr) const;
  // Reverses the order of unicodes within the box. If Pango generates a
  // ligature, these will get reversed on output, so reverse now.
  void ReverseUnicodesInBox();

  static void TranslateBoxes(int xshift, int yshift,
                             std::vector<BoxChar*>* boxes);

  // Prepares for writing the boxes to a file by inserting newlines, spaces,
  // and re-ordering so the boxes are strictly left-to-right.
  static void PrepareToWrite(std::vector<BoxChar*>* boxes);
  // Inserts newline (tab) characters into the vector at newline positions.
  static void InsertNewlines(bool rtl_rules, bool vertical_rules,
                             std::vector<BoxChar*>* boxes);
  // Converts nullptr boxes to space characters, with appropriate bounding
  // boxes.
  static void InsertSpaces(bool rtl_rules, bool vertical_rules,
                           std::vector<BoxChar*>* boxes);
  // Reorders text in a right-to-left script in left-to-right order.
  static void ReorderRTLText(std::vector<BoxChar*>* boxes);
  // Returns true if the vector contains mostly RTL characters.
  static bool ContainsMostlyRTL(const std::vector<BoxChar*>& boxes);
  // Returns true if the text is mostly laid out vertically.
  static bool MostlyVertical(const std::vector<BoxChar*>& boxes);

  // Returns the total length of all the strings in the boxes.
  static int TotalByteLength(const std::vector<BoxChar*>& boxes);

  // Rotate the vector of boxes between start and end by the given rotation.
  // The rotation is in radians clockwise about the given center.
  static void RotateBoxes(float rotation,
                          int xcenter,
                          int ycenter,
                          int start_box,
                          int end_box,
                          std::vector<BoxChar*>* boxes);

  // Create a tesseract box file from the vector of boxes. The image height
  // is needed to convert to tesseract coordinates.
  static void WriteTesseractBoxFile(const std::string& name, int height,
                                    const std::vector<BoxChar*>& boxes);
  // Gets the tesseract box file as a string from the vector of boxes.
  // The image height is needed to convert to tesseract coordinates.
  static std::string GetTesseractBoxStr(int height,
                                        const std::vector<BoxChar*>& boxes);

 private:
  std::string ch_;
  Box* box_;
  int page_;
  // If the box is an RTL character, contains the original position in the
  // array of boxes (before reversal), otherwise -1.
  int rtl_index_;
};

// Sort predicate to sort a vector of BoxChar*.
struct BoxCharPtrSort {
  bool operator()(const BoxChar* box1, const BoxChar* box2) const {
    if (box1->rtl_index() >= 0 && box2->rtl_index() >= 0)
      return box2->rtl_index() < box1->rtl_index();
    return *box1 < *box2;
  }
};

}  // namespace tesseract

#endif  // TESSERACT_TRAINING_BOXCHAR_H_