angular_bounds_filter.h

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* Author: Eitan Marder-Eppstein
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#ifndef LASER_SCAN_ANGULAR_BOUNDS_FILTER_H
#define LASER_SCAN_ANGULAR_BOUNDS_FILTER_H
 
#include <filters/filter_base.hpp>
#include <sensor_msgs/LaserScan.h>
 
namespace laser_filters
{
  class LaserScanAngularBoundsFilter : public filters::FilterBase<sensor_msgs::LaserScan>
  {
    public:
      double lower_angle_;
      double upper_angle_;
 
      bool configure()
      {
        lower_angle_ = 0;
        upper_angle_ = 0;
 
        if(!getParam("lower_angle", lower_angle_) || !getParam("upper_angle", upper_angle_)){
          ROS_ERROR("Both the lower_angle and upper_angle parameters must be set to use this filter.");
          return false;
        }
 
        return true;
      }
 
      virtual ~LaserScanAngularBoundsFilter(){}
 
      bool update(const sensor_msgs::LaserScan& input_scan, sensor_msgs::LaserScan& filtered_scan){
        filtered_scan.ranges.resize(input_scan.ranges.size());
        filtered_scan.intensities.resize(input_scan.intensities.size());
 
        double start_angle = input_scan.angle_min;
        double current_angle = input_scan.angle_min;
        ros::Time start_time = input_scan.header.stamp;
        unsigned int count = 0;
        //loop through the scan and truncate the beginning and the end of the scan as necessary
        for(unsigned int i = 0; i < input_scan.ranges.size(); ++i){
          if(input_scan.angle_increment > 0){ //if the laserscanner turns counterclockwise
            //wait until we get to our desired starting angle
            if(start_angle < lower_angle_){
              start_angle += input_scan.angle_increment;
              current_angle += input_scan.angle_increment;
              start_time += ros::Duration(input_scan.time_increment);
            }
            else{
              filtered_scan.ranges[count] = input_scan.ranges[i];
 
              //make sure  that we don't update intensity data if its not available
              if(input_scan.intensities.size() > i)
                filtered_scan.intensities[count] = input_scan.intensities[i];
 
              count++;
 
              //check if we need to break out of the loop, basically if the next increment will put us over the threshold
              if(current_angle + input_scan.angle_increment > upper_angle_){
                break;
              }
              current_angle += input_scan.angle_increment;
            }
          }
          else{ //the laserscanner turns clockwise
            //wait until we get to our desired starting angle
            if(start_angle > upper_angle_){
              start_angle += input_scan.angle_increment;
              current_angle += input_scan.angle_increment;
              start_time += ros::Duration(input_scan.time_increment);
            }
            else{
              filtered_scan.ranges[count] = input_scan.ranges[i];
 
              //make sure  that we don't update intensity data if its not available
              if(input_scan.intensities.size() > i)
                filtered_scan.intensities[count] = input_scan.intensities[i];
 
              count++;
 
              //check if we need to break out of the loop, basically if the next increment will put us over the threshold
              if(current_angle + input_scan.angle_increment < lower_angle_){
                break;
              }
 
              current_angle += input_scan.angle_increment;
 
            }
          }
        }
 
        //make sure to set all the needed fields on the filtered scan
        filtered_scan.header.frame_id = input_scan.header.frame_id;
        filtered_scan.header.stamp = start_time;
        filtered_scan.angle_min = start_angle;
        filtered_scan.angle_max = current_angle;
        filtered_scan.angle_increment = input_scan.angle_increment;
        filtered_scan.time_increment = input_scan.time_increment;
        filtered_scan.scan_time = input_scan.scan_time;
        filtered_scan.range_min = input_scan.range_min;
        filtered_scan.range_max = input_scan.range_max;
 
        filtered_scan.ranges.resize(count);
 
        if(input_scan.intensities.size() >= count)
          filtered_scan.intensities.resize(count);
 
        ROS_DEBUG("Filtered out %d points from the laser scan.", (int)input_scan.ranges.size() - (int)count);
 
        return true;
 
      }
  };
};
#endif