intensity_filter.h

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#ifndef LASER_SCAN_INTENSITY_FILTER_H
#define LASER_SCAN_INTENSITY_FILTER_H

#include "filters/filter_base.h"
#include "sensor_msgs/LaserScan.h"

namespace laser_filters
{

class LaserScanIntensityFilter : public filters::FilterBase<sensor_msgs::LaserScan>
{
public:

  double lower_threshold_ ;
  double upper_threshold_ ;
  int disp_hist_ ;
  bool disp_hist_enabled_;

  bool configure()
  {
    lower_threshold_ = 8000.0;
    upper_threshold_ = 100000.0;
    disp_hist_ = 1;
    getParam("lower_threshold", lower_threshold_);
    getParam("upper_threshold", upper_threshold_) ;
    getParam("disp_histogram",  disp_hist_) ;

    disp_hist_enabled_ = (disp_hist_ == 0) ? false : true;

    return true;
  }

  virtual ~LaserScanIntensityFilter(){}

  bool update(const sensor_msgs::LaserScan& input_scan, sensor_msgs::LaserScan& filtered_scan)
  {
    const double hist_max = 4*12000.0 ;
    const int num_buckets = 24 ;
    int histogram[num_buckets] ;
    for (int i=0; i < num_buckets; i++)
      histogram[i] = 0 ;

    filtered_scan = input_scan;

    // Need to check ever reading in the current scan
    for (unsigned int i=0;
         i < input_scan.ranges.size() && i < input_scan.intensities.size();
         i++)
    {
      // Is this reading below our lower threshold?
      // Is this reading above our upper threshold?
      if (filtered_scan.intensities[i] <= lower_threshold_ ||
          filtered_scan.intensities[i] >= upper_threshold_)
      {
        // If so, then make it an invalid value (NaN)
        filtered_scan.ranges[i] = std::numeric_limits<float>::quiet_NaN();
      }

      // Calculate histogram
      if (disp_hist_enabled_){
        // If intensity value is inf or NaN, skip voting histogram
        if( std::isinf((double)filtered_scan.intensities[i]) ||
            std::isnan((double)filtered_scan.intensities[i]) )
          continue;

        // Choose bucket to vote on histogram,
        // and check the index of bucket is in the histogram array
        int cur_bucket = (int)(filtered_scan.intensities[i] / hist_max * num_buckets);
        if (cur_bucket > num_buckets-1)
          cur_bucket = num_buckets-1;
        else if (cur_bucket < 0) cur_bucket = 0;
        histogram[cur_bucket]++;
      }
    }

    // Display Histogram
    if (disp_hist_enabled_)
    {
      printf("********** SCAN **********\n") ;
      for (int i=0; i < num_buckets; i++)
      {
        printf("%u - %u: %u\n", (unsigned int) hist_max/num_buckets*i,
                                (unsigned int) hist_max/num_buckets*(i+1),
                                histogram[i]) ;
      }
    }
    return true;
  }
};
}

#endif // LASER_SCAN_INTENSITY_FILTER_H