source: trunk/src/Detection/lutz_detect.cc

// -----------------------------------------------------------------------
// lutz_detect.cc: Search a 2D Image for objects.
// -----------------------------------------------------------------------
// Copyright (C) 2006, Matthew Whiting, ATNF
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// Duchamp is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with Duchamp; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
//
// Correspondence concerning Duchamp may be directed to:
//    Internet email: Matthew.Whiting [at] atnf.csiro.au
//    Postal address: Dr. Matthew Whiting
//                    Australia Telescope National Facility, CSIRO
//                    PO Box 76
//                    Epping NSW 1710
//                    AUSTRALIA
// -----------------------------------------------------------------------
#include <duchamp/Detection/finders.hh>
#include <duchamp/PixelMap/Voxel.hh>
#include <duchamp/PixelMap/Object2D.hh>
#include <vector>

using namespace PixelInfo;

/// @brief Enumeration to describe status of a pixel or a detected object
enum STATUS { NONOBJECT, ///< Pixel not above the threshold.
              OBJECT,    ///< Pixel above the threshold.
              COMPLETE,  ///< Object is complete
              INCOMPLETE ///< Object not yet complete
};

/// @brief Simple enumeration to enable obvious reference to current or prior row.
enum ROW { PRIOR=0, CURRENT};

/// @brief A couple of null values: the default starting value for markers, and one used for debugging.
enum NULLS { NULLSTART=-1, ///< Default start/end value, obviously
                           ///   outside valid range.
             NULLMARKER=45 ///< ASCII 45 = '-', which eases printing
                           ///   for debugging purposes
}; 

//---------------------------
/// @brief
/// A simple class local to @file to help manage detected
/// objects.
/// 
/// @details Keeps a track of a detection, as well as the start and finish
/// locations of the detection on the current row.
/// 
class FoundObject{
public:
  /// @brief Basic constructor, setting the start & end to NULL values. 
  FoundObject(){start=NULLSTART; end=NULLSTART;};
  int start; ///< Pixel on the current row where the detection starts.
  int end;   ///< Pixel on the current row where the detection finishes.
  Object2D info; ///< Collection of detected pixels.
};
//---------------------------

namespace duchamp
{

  std::vector<Object2D> lutz_detect(std::vector<bool> &array, size_t xdim, size_t ydim, unsigned int minSize) 
  {
    /// @details
    ///  A detection algorithm for 2-dimensional images based on that of
    ///  Lutz (1980).
    ///  
    ///  The image is raster-scanned, and searched row-by-row. Objects
    ///  detected in each row are compared to objects in subsequent rows,
    ///  and combined if they are connected (in an 8-fold sense).
    /// 

    // Allocate necessary arrays.
    std::vector<Object2D> outputlist;
    STATUS *status  = new STATUS[2];
    Object2D *store = new Object2D[xdim+1];
    char *marker    = new char[xdim+1];
    for(size_t i=0; i<(xdim+1); i++) marker[i] = NULLMARKER;
    std::vector<FoundObject> oS;
    std::vector<STATUS>      psS;

    size_t loc=0;

    for(size_t posY=0;posY<(ydim+1);posY++){
      // Loop over each row -- consider rows one at a time
    
      status[PRIOR] = COMPLETE;
      status[CURRENT] = NONOBJECT;

      for(size_t posX=0;posX<(xdim+1);posX++){
        // Now the loop for a given row, looking at each column individually.

        char currentMarker = marker[posX];
        marker[posX] = NULLMARKER;

        bool isObject;
        if((posX<xdim)&&(posY<ydim)){ 
          // if we are in the original image
          isObject = array[loc++];
        }
        else isObject = false;
        // else we're in the padding row/col and isObject=FALSE;

        // 
        // ------------------------------ START SEGMENT ------------------------
        // If the current pixel is object and the previous pixel is not, then
        // start a new segment.
        // If the pixel touches an object on the prior row, the marker is either
        // an S or an s, depending on whether the object has started yet.
        // If it doesn't touch a prior object, this is the start of a completly
        // new object on this row.
        // 
        if ( (isObject) && (status[CURRENT] != OBJECT) ){

          status[CURRENT] = OBJECT;
          if(status[PRIOR] == OBJECT){
          
            if(oS.back().start==NULLSTART){
              marker[posX] = 'S';
              oS.back().start = int(posX);
            }
            else  marker[posX] = 's';
          }
          else{
            psS.push_back(status[PRIOR]);  //PUSH PS onto PSSTACK;
            marker[posX] = 'S';
            oS.resize(oS.size()+1);        //PUSH OBSTACK;
            oS.back().start = int(posX);

            status[PRIOR] = COMPLETE;
          }
        }

        // 
        // ------------------------------ PROCESS MARKER -----------------------
        // If the current marker is not blank, then we need to deal with it. 
        // Four cases:
        //   S --> start of object on prior row. Push priorStatus onto PSSTACK 
        //         and set priorStatus to OBJECT
        //   s --> start of a secondary segment of object on prior row.
        //         If current object joined, pop PSSTACK and join the objects.
        //       Set priorStatus to OBJECT.
        //   f --> end of a secondary segment of object on prior row.
        //         Set priorStatus to INCOMPLETE.
        //   F --> end of object on prior row. If no more of the object is to 
        //          come (priorStatus=COMPLETE), then finish it and output data.
        //         Add to list, but only if it has more than the minimum number
        //           of pixels.
        // 
        if(currentMarker != NULLMARKER){

          if(currentMarker == 'S'){
            psS.push_back(status[PRIOR]);      // PUSH PS onto PSSTACK
            if(status[CURRENT] == NONOBJECT){
              psS.push_back(COMPLETE);         // PUSH COMPLETE ONTO PSSTACK;
              oS.resize(oS.size()+1);          // PUSH OBSTACK;
              oS.back().info = store[posX];
            }
            else oS.back().info = oS.back().info + store[posX];
          
            status[PRIOR] = OBJECT;
          }

          /*---------*/
          if(currentMarker == 's'){

            if( (status[CURRENT] == OBJECT) && (status[PRIOR] == COMPLETE) ){
              status[PRIOR] = psS.back();
              psS.pop_back();                   //POP PSSTACK ONTO PS

              //            oS.at(oS.size()-2).info.addAnObject( oS.back().info );
              //            if(oS.at(oS.size()-2).start == NULLSTART) 
              //              oS.at(oS.size()-2).start = oS.back().start;
              //            else marker[oS.back().start] = 's';

              oS[oS.size()-2].info = oS[oS.size()-2].info + oS.back().info;
              if(oS[oS.size()-2].start == NULLSTART) 
                oS[oS.size()-2].start = oS.back().start;
              else marker[oS.back().start] = 's';

              oS.pop_back();
            }

            status[PRIOR] = OBJECT;
          }

          /*---------*/
          if(currentMarker == 'f') status[PRIOR] = INCOMPLETE;

          /*---------*/
          if(currentMarker == 'F') {

            status[PRIOR] = psS.back();
            psS.pop_back();                    //POP PSSTACK ONTO PS

            if( (status[CURRENT] == NONOBJECT) && (status[PRIOR] == COMPLETE) ){

              if(oS.back().start == NULLSTART){ 
                // The object is completed. If it is big enough, add to
                // the end of the output list.        
                if(oS.back().info.getSize() >= minSize){ 
                  //oS.back().info.calcParams(); // work out midpoints, fluxes etc
                  outputlist.push_back(oS.back().info);
                }
              }
              else{
                marker[ oS.back().end ] = 'F';
                store[ oS.back().start ] = oS.back().info;
              }

              oS.pop_back();

              status[PRIOR] = psS.back();
              psS.pop_back();
            }
          }

        } // end of PROCESSMARKER section ( if(currentMarker!=NULLMARKER) )

        if (isObject){
          oS.back().info.addPixel(long(posX),long(posY));
        }
        else{
          // 
          // ----------------------------- END SEGMENT -------------------------
          // If the current pixel is background and the previous pixel was an 
          // object, then finish the segment.
          // If the prior status is COMPLETE, it's the end of the final segment 
          // of the object section.
          // If not, it's end of the segment, but not necessarily the section.
          // 
          if ( status[CURRENT] == OBJECT) {

            status[CURRENT] = NONOBJECT;

            if(status[PRIOR] != COMPLETE){
              marker[posX] = 'f';
              oS.back().end = int(posX);
            }
            else{
              status[PRIOR] = psS.back();
              psS.pop_back();                   //POP PSSTACK onto PS;
              marker[posX] = 'F';
              store[ oS.back().start ] = oS.back().info;
              oS.pop_back();
            }
          }
        
        } //-> end of END SEGMENT else{ clause

      }//-> end of loop over posX

    }//-> end of loop over posY

    // clean up and remove declared arrays
    delete [] marker;
    delete [] store;
    delete [] status;

    return outputlist;

  }

}