Added LaserScanBinningFilter: places measurements into fixed number of bins.

include/laser_filters/binning_filter.h

@@ -0,0 +1,114 @@
+/*********************************************************************
+* Software License Agreement (BSD License)
+* 
+*  Copyright (c) 2024, Anthony Goeckner <[email protected]>
+*  All rights reserved.
+* 
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+
+#ifndef BINNING_FILTER_H
+#define BINNING_FILTER_H
+/**
+\author Anthony Goeckner
+@b LaserScanBinningFilter splits input scans into bins, ensuring that every output scan has the exact same number of readings as the number of bins.
+
+**/
+
+#include "filters/filter_base.hpp"
+
+#include <sensor_msgs/msg/laser_scan.hpp>
+
+namespace laser_filters
+{
+
+class LaserScanBinningFilter : public filters::FilterBase<sensor_msgs::msg::LaserScan>
+{
+public:
+
+  uint num_bins_;
+
+  bool configure()
+  {
+    num_bins_ = 360;
+    getParam("num_bins", num_bins_);
+
+    return true;
+  }
+
+  virtual ~LaserScanBinningFilter()
+  { 
+  }
+
+  bool update(const sensor_msgs::msg::LaserScan& input_scan, sensor_msgs::msg::LaserScan& filtered_scan)
+  {
+    // Copy data first.
+    filtered_scan = input_scan;
+
+    // Set up filtered_scan.
+    filtered_scan.ranges.assign(num_bins_, std::numeric_limits<float>::quiet_NaN());
+    filtered_scan.intensities.assign(num_bins_, std::numeric_limits<float>::quiet_NaN());
+    filtered_scan.angle_increment = 2.0 * M_PI / static_cast<float>(num_bins_);
+
+    // Convert to positive angles.
+    float input_angle_min = fmodf(2.0 * M_PI + input_scan.angle_min, 2.0 * M_PI);
+
+    // Need to account for case where scan wraps around, causing the data at angle 0 to actually occur
+    // at the end of the scan. Therefore, we need to adjust the starting point of the scan.
+    double angle_overlap = fmodf(input_scan.angle_increment * input_scan.ranges.size(), 2.0 * M_PI);
+
+    // Update the scan time and angle_min to the oldest reading which will not be overlapped by a newer one.
+    filtered_scan.scan_time = input_scan.scan_time + input_scan.time_increment * angle_overlap / input_scan.angle_increment;
+    filtered_scan.time_increment = input_scan.time_increment * (num_bins_ * 2.0 * M_PI) / (input_scan.ranges.size() * input_scan.angle_increment);
+    filtered_scan.angle_min = fmodf(input_angle_min + angle_overlap, 2.0 * M_PI);
+    filtered_scan.angle_max = filtered_scan.angle_min + 2.0 * M_PI;
+
+    // Assign data to bins.
+    unsigned int i = 0;
+    while(i < input_scan.ranges.size())
+    {
+      // Calculate angle.
+      double input_angle_relative = input_scan.angle_increment * i;
+      double angle = fmodf(input_angle_relative - angle_overlap + 2.0 * M_PI, 2.0 * M_PI);
+
+      // Calculate the bin index.
+      unsigned int bin_index = static_cast<unsigned int>(floor(angle / filtered_scan.angle_increment));
+
+      // Copy the range and intensity values.
+      filtered_scan.ranges[bin_index] = input_scan.ranges[i];
+      filtered_scan.intensities[bin_index] = input_scan.intensities[i];
+
+      i++;
+    }
+    return true;
+  }
+};
+
+}
+
+#endif // LASER_SCAN_INTENSITY_FILTER_H

laser_filters_plugins.xml

@@ -30,6 +30,12 @@
       This is a filter that will generate range readings for error readings in a scan by interpolating between valid readings on either side of the error
       </description>
     </class>
+    <class name="laser_filters/LaserScanBinningFilter" type="laser_filters::LaserScanBinningFilter" 
+	    base_class_type="filters::FilterBase&lt;sensor_msgs::msg::LaserScan&gt;">
+      <description>
+	      This is a filter that bins laser scans such that the output always contains a fixed number of measurements.
+      </description>
+    </class>
     <class name="laser_filters/LaserScanAngularBoundsFilter" type="laser_filters::LaserScanAngularBoundsFilter" 
 	    base_class_type="filters::FilterBase&lt;sensor_msgs::msg::LaserScan&gt;">
       <description>

src/laser_scan_filters.cpp

@@ -30,6 +30,7 @@
 #include "laser_filters/median_filter.h"
 #include "laser_filters/median_spatial_filter.h"
 #include "laser_filters/array_filter.h"
+#include "laser_filters/binning_filter.h"
 #include "laser_filters/intensity_filter.h"
 #include "laser_filters/range_filter.h"
 #include "laser_filters/scan_mask_filter.h"
@@ -52,6 +53,7 @@
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserMedianFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanMedianSpatialFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserArrayFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
+PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanBinningFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanIntensityFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanRangeFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanAngularBoundsFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)