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  #ifndef __OPENCV_TEXT_ERFILTER_HPP__
  #define __OPENCV_TEXT_ERFILTER_HPP__
  
  #include "opencv2/core.hpp"
  #include <vector>
  #include <deque>
  #include <string>
  
  namespace cv
  {
  namespace text
  {
  
  //! @addtogroup text_detect
  //! @{
  
  /** @brief The ERStat structure represents a class-specific Extremal Region (ER).
  
  An ER is a 4-connected set of pixels with all its grey-level values smaller than the values in its
  outer boundary. A class-specific ER is selected (using a classifier) from all the ER's in the
  component tree of the image. :
   */
  struct CV_EXPORTS ERStat
  {
  public:
      //! Constructor
      explicit ERStat(int level = 256, int pixel = 0, int x = 0, int y = 0);
      //! Destructor
      ~ERStat() { }
  
      //! seed point and the threshold (max grey-level value)
      int pixel;
      int level;
  
      //! incrementally computable features
      int area;
      int perimeter;
      int euler;                 //!< euler number
      Rect rect;
      double raw_moments[2];     //!< order 1 raw moments to derive the centroid
      double central_moments[3]; //!< order 2 central moments to construct the covariance matrix
      std::deque<int> *crossings;//!< horizontal crossings
      float med_crossings;       //!< median of the crossings at three different height levels
  
      //! 2nd stage features
      float hole_area_ratio;
      float convex_hull_ratio;
      float num_inflexion_points;
  
      // TODO Other features can be added (average color, standard deviation, and such)
  
  
      // TODO shall we include the pixel list whenever available (i.e. after 2nd stage) ?
      std::vector<int> *pixels;
  
      //! probability that the ER belongs to the class we are looking for
      double probability;
  
      //! pointers preserving the tree structure of the component tree
      ERStat* parent;
      ERStat* child;
      ERStat* next;
      ERStat* prev;
  
      //! wenever the regions is a local maxima of the probability
      bool local_maxima;
      ERStat* max_probability_ancestor;
      ERStat* min_probability_ancestor;
  };
  
  /** @brief Base class for 1st and 2nd stages of Neumann and Matas scene text detection algorithm [Neumann12]. :
  
  Extracts the component tree (if needed) and filter the extremal regions (ER's) by using a given classifier.
   */
  class CV_EXPORTS_W ERFilter : public Algorithm
  {
  public:
  
      /** @brief Callback with the classifier is made a class.
  
      By doing it we hide SVM, Boost etc. Developers can provide their own classifiers to the
      ERFilter algorithm.
       */
      class CV_EXPORTS_W Callback
      {
      public:
          virtual ~Callback() { }
          /** @brief The classifier must return probability measure for the region.
  
          @param  stat :   The region to be classified
           */
          virtual double eval(const ERStat& stat) = 0; //const = 0; //TODO why cannot use const = 0 here?
      };
  
      /** @brief The key method of ERFilter algorithm.
  
      Takes image on input and returns the selected regions in a vector of ERStat only distinctive
      ERs which correspond to characters are selected by a sequential classifier
  
      @param image Single channel image CV_8UC1
  
      @param regions Output for the 1st stage and Input/Output for the 2nd. The selected Extremal Regions
      are stored here.
  
      Extracts the component tree (if needed) and filter the extremal regions (ER's) by using a given
      classifier.
       */
      virtual void run( InputArray image, std::vector<ERStat>& regions ) = 0;
  
  
      //! set/get methods to set the algorithm properties,
      virtual void setCallback(const Ptr<ERFilter::Callback>& cb) = 0;
      virtual void setThresholdDelta(int thresholdDelta) = 0;
      virtual void setMinArea(float minArea) = 0;
      virtual void setMaxArea(float maxArea) = 0;
      virtual void setMinProbability(float minProbability) = 0;
      virtual void setMinProbabilityDiff(float minProbabilityDiff) = 0;
      virtual void setNonMaxSuppression(bool nonMaxSuppression) = 0;
      virtual int  getNumRejected() = 0;
  };
  
  
  /*!
      Create an Extremal Region Filter for the 1st stage classifier of N&M algorithm
      Neumann L., Matas J.: Real-Time Scene Text Localization and Recognition, CVPR 2012
  
      The component tree of the image is extracted by a threshold increased step by step
      from 0 to 255, incrementally computable descriptors (aspect_ratio, compactness,
      number of holes, and number of horizontal crossings) are computed for each ER
      and used as features for a classifier which estimates the class-conditional
      probability P(er|character). The value of P(er|character) is tracked using the inclusion
      relation of ER across all thresholds and only the ERs which correspond to local maximum
      of the probability P(er|character) are selected (if the local maximum of the
      probability is above a global limit pmin and the difference between local maximum and
      local minimum is greater than minProbabilityDiff).
  
      @param cb – Callback with the classifier. Default classifier can be implicitly load with function
          loadClassifierNM1(), e.g. from file in samples/cpp/trained_classifierNM1.xml
      @param thresholdDelta – Threshold step in subsequent thresholds when extracting the component tree
      @param minArea – The minimum area (% of image size) allowed for retreived ER’s
      @param maxArea – The maximum area (% of image size) allowed for retreived ER’s
      @param minProbability – The minimum probability P(er|character) allowed for retreived ER’s
      @param nonMaxSuppression – Whenever non-maximum suppression is done over the branch probabilities
      @param minProbabilityDiff – The minimum probability difference between local maxima and local minima ERs
  */
  
  /** @brief Create an Extremal Region Filter for the 1st stage classifier of N&M algorithm [Neumann12].
  
  @param  cb :   Callback with the classifier. Default classifier can be implicitly load with function
  loadClassifierNM1, e.g. from file in samples/cpp/trained_classifierNM1.xml
  @param  thresholdDelta :   Threshold step in subsequent thresholds when extracting the component tree
  @param  minArea :   The minimum area (% of image size) allowed for retreived ER's
  @param  minArea :   The maximum area (% of image size) allowed for retreived ER's
  @param  minProbability :   The minimum probability P(er|character) allowed for retreived ER's
  @param  nonMaxSuppression :   Whenever non-maximum suppression is done over the branch probabilities
  @param  minProbability :   The minimum probability difference between local maxima and local minima ERs
  
  The component tree of the image is extracted by a threshold increased step by step from 0 to 255,
  incrementally computable descriptors (aspect_ratio, compactness, number of holes, and number of
  horizontal crossings) are computed for each ER and used as features for a classifier which estimates
  the class-conditional probability P(er|character). The value of P(er|character) is tracked using the
  inclusion relation of ER across all thresholds and only the ERs which correspond to local maximum of
  the probability P(er|character) are selected (if the local maximum of the probability is above a
  global limit pmin and the difference between local maximum and local minimum is greater than
  minProbabilityDiff).
   */
  CV_EXPORTS_W Ptr<ERFilter> createERFilterNM1(const Ptr<ERFilter::Callback>& cb,
                                                    int thresholdDelta = 1, float minArea = (float)0.00025,
                                                    float maxArea = (float)0.13, float minProbability = (float)0.4,
                                                    bool nonMaxSuppression = true,
                                                    float minProbabilityDiff = (float)0.1);
  
  /** @brief Create an Extremal Region Filter for the 2nd stage classifier of N&M algorithm [Neumann12].
  
  @param  cb :   Callback with the classifier. Default classifier can be implicitly load with function
  loadClassifierNM2, e.g. from file in samples/cpp/trained_classifierNM2.xml
  @param  minProbability :   The minimum probability P(er|character) allowed for retreived ER's
  
  In the second stage, the ERs that passed the first stage are classified into character and
  non-character classes using more informative but also more computationally expensive features. The
  classifier uses all the features calculated in the first stage and the following additional
  features: hole area ratio, convex hull ratio, and number of outer inflexion points.
   */
  CV_EXPORTS_W Ptr<ERFilter> createERFilterNM2(const Ptr<ERFilter::Callback>& cb,
                                                    float minProbability = (float)0.3);
  
  
  /** @brief Allow to implicitly load the default classifier when creating an ERFilter object.
  
  @param filename The XML or YAML file with the classifier model (e.g. trained_classifierNM1.xml)
  
  returns a pointer to ERFilter::Callback.
   */
  CV_EXPORTS_W Ptr<ERFilter::Callback> loadClassifierNM1(const String& filename);
  
  /** @brief Allow to implicitly load the default classifier when creating an ERFilter object.
  
  @param filename The XML or YAML file with the classifier model (e.g. trained_classifierNM2.xml)
  
  returns a pointer to ERFilter::Callback.
   */
  CV_EXPORTS_W Ptr<ERFilter::Callback> loadClassifierNM2(const String& filename);
  
  
  //! computeNMChannels operation modes
  enum { ERFILTER_NM_RGBLGrad,
         ERFILTER_NM_IHSGrad
       };
  
  /** @brief Compute the different channels to be processed independently in the N&M algorithm [Neumann12].
  
  @param _src Source image. Must be RGB CV_8UC3.
  
  @param _channels Output vector\<Mat\> where computed channels are stored.
  
  @param _mode Mode of operation. Currently the only available options are:
  **ERFILTER_NM_RGBLGrad** (used by default) and **ERFILTER_NM_IHSGrad**.
  
  In N&M algorithm, the combination of intensity (I), hue (H), saturation (S), and gradient magnitude
  channels (Grad) are used in order to obtain high localization recall. This implementation also
  provides an alternative combination of red (R), green (G), blue (B), lightness (L), and gradient
  magnitude (Grad).
   */
  CV_EXPORTS_W void computeNMChannels(InputArray _src, CV_OUT OutputArrayOfArrays _channels, int _mode = ERFILTER_NM_RGBLGrad);
  
  
  
  //! text::erGrouping operation modes
  enum erGrouping_Modes {
  
      /** Exhaustive Search algorithm proposed in [Neumann11] for grouping horizontally aligned text.
      The algorithm models a verification function for all the possible ER sequences. The
      verification fuction for ER pairs consists in a set of threshold-based pairwise rules which
      compare measurements of two regions (height ratio, centroid angle, and region distance). The
      verification function for ER triplets creates a word text line estimate using Least
      Median-Squares fitting for a given triplet and then verifies that the estimate is valid (based
      on thresholds created during training). Verification functions for sequences larger than 3 are
      approximated by verifying that the text line parameters of all (sub)sequences of length 3 are
      consistent.
      */
      ERGROUPING_ORIENTATION_HORIZ,
      /** Text grouping method proposed in [Gomez13][Gomez14] for grouping arbitrary oriented text. Regions
      are agglomerated by Single Linkage Clustering in a weighted feature space that combines proximity
      (x,y coordinates) and similarity measures (color, size, gradient magnitude, stroke width, etc.).
      SLC provides a dendrogram where each node represents a text group hypothesis. Then the algorithm
      finds the branches corresponding to text groups by traversing this dendrogram with a stopping rule
      that combines the output of a rotation invariant text group classifier and a probabilistic measure
      for hierarchical clustering validity assessment.
       */
      ERGROUPING_ORIENTATION_ANY
  };
  
  /** @brief Find groups of Extremal Regions that are organized as text blocks.
  
  @param img Original RGB or Greyscale image from wich the regions were extracted.
  
  @param channels Vector of single channel images CV_8UC1 from wich the regions were extracted.
  
  @param regions Vector of ER's retreived from the ERFilter algorithm from each channel.
  
  @param groups The output of the algorithm is stored in this parameter as set of lists of indexes to
  provided regions.
  
  @param groups_rects The output of the algorithm are stored in this parameter as list of rectangles.
  
  @param method Grouping method (see text::erGrouping_Modes). Can be one of ERGROUPING_ORIENTATION_HORIZ,
  ERGROUPING_ORIENTATION_ANY.
  
  @param filename The XML or YAML file with the classifier model (e.g.
  samples/trained_classifier_erGrouping.xml). Only to use when grouping method is
  ERGROUPING_ORIENTATION_ANY.
  
  @param minProbablity The minimum probability for accepting a group. Only to use when grouping
  method is ERGROUPING_ORIENTATION_ANY.
   */
  CV_EXPORTS void erGrouping(InputArray img, InputArrayOfArrays channels,
                                             std::vector<std::vector<ERStat> > &regions,
                                             std::vector<std::vector<Vec2i> > &groups,
                                             std::vector<Rect> &groups_rects,
                                             int method = ERGROUPING_ORIENTATION_HORIZ,
                                             const std::string& filename = std::string(),
                                             float minProbablity = 0.5);
  
  CV_EXPORTS_W void erGrouping(InputArray image, InputArray channel,
                                             std::vector<std::vector<Point> > regions,
                                             CV_OUT std::vector<Rect> &groups_rects,
                                             int method = ERGROUPING_ORIENTATION_HORIZ,
                                             const String& filename = String(),
                                             float minProbablity = (float)0.5);
  
  /** @brief Converts MSER contours (vector\<Point\>) to ERStat regions.
  
  @param image Source image CV_8UC1 from which the MSERs where extracted.
  
  @param contours Intput vector with all the contours (vector\<Point\>).
  
  @param regions Output where the ERStat regions are stored.
  
  It takes as input the contours provided by the OpenCV MSER feature detector and returns as output
  two vectors of ERStats. This is because MSER() output contains both MSER+ and MSER- regions in a
  single vector\<Point\>, the function separates them in two different vectors (this is as if the
  ERStats where extracted from two different channels).
  
  An example of MSERsToERStats in use can be found in the text detection webcam_demo:
  <https://github.com/opencv/opencv_contrib/blob/master/modules/text/samples/webcam_demo.cpp>
   */
  CV_EXPORTS void MSERsToERStats(InputArray image, std::vector<std::vector<Point> > &contours,
                                 std::vector<std::vector<ERStat> > &regions);
  
  // Utility funtion for scripting
  CV_EXPORTS_W void detectRegions(InputArray image, const Ptr<ERFilter>& er_filter1, const Ptr<ERFilter>& er_filter2, CV_OUT std::vector< std::vector<Point> >& regions);
  
  //! @}
  
  }
  }
  #endif // _OPENCV_TEXT_ERFILTER_HPP_
  