Spatial median filter

examples/median_spatial_filter.launch.py

@@ -0,0 +1,18 @@
+from launch import LaunchDescription
+from launch.substitutions import PathJoinSubstitution
+from launch_ros.actions import Node
+from ament_index_python.packages import get_package_share_directory
+
+
+def generate_launch_description():
+    return LaunchDescription([
+        Node(
+            package="laser_filters",
+            executable="scan_to_scan_filter_chain",
+            parameters=[
+                PathJoinSubstitution([
+                    get_package_share_directory("laser_filters"),
+                    "examples", "median_spatial_filter_example.yaml",
+                ])],
+        )
+    ])

examples/median_spatial_filter.launch.xml

@@ -0,0 +1,5 @@
+<launch>
+    <node name="scan_to_scan_filter_chain" pkg="laser_filters" exec="scan_to_scan_filter_chain" output="screen">
+        <param from="$(find-pkg-share laser_filters)/examples/median_spatial_filter_example.yaml" />
+    </node>
+</launch>

examples/median_spatial_filter_example.yaml

@@ -0,0 +1,17 @@
+scan_to_scan_filter_chain:
+  ros__parameters:
+    filter1:
+      name: median_spatial
+      type: laser_filters/LaserScanMedianSpatialFilter
+      params:
+        window_size: 31
+    filter2:
+      name: median_filter
+      type: laser_filters/LaserArrayFilter
+      params:
+        range_filter_chain:
+          filter1:
+            name: median
+            type: filters/MultiChannelMedianFilterFloat
+            params:
+              number_of_observations: 3

include/laser_filters/median_spatial_filter.h

@@ -0,0 +1,157 @@
+/*********************************************************************
+* Software License Agreement (BSD License)
+*
+*  Copyright (c) 2017, laser_filters authors
+*  All rights reserved.
+*
+*  Redistribution and use in source and binary forms, with or without
+*  modification, are permitted provided that the following conditions
+*  are met:
+*
+*   * Redistributions of source code must retain the above copyright
+*     notice, this list of conditions and the following disclaimer.
+*   * Redistributions in binary form must reproduce the above
+*     copyright notice, this list of conditions and the following
+*     disclaimer in the documentation and/or other materials provided
+*     with the distribution.
+*   * Neither the name of the Willow Garage nor the names of its
+*     contributors may be used to endorse or promote products derived
+*     from this software without specific prior written permission.
+*
+*  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+*  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+*  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+*  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+*  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+*  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+*  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+*  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+*  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+*  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+*  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+*  POSSIBILITY OF SUCH DAMAGE.
+*********************************************************************/
+
+/*
+\author Yannic Bachmann
+*/
+
+#ifndef LASER_SCAN_MEDIAN_SPATIAL_FILTER_H
+#define LASER_SCAN_MEDIAN_SPATIAL_FILTER_H
+
+#include "filters/filter_base.hpp"
+#include <sensor_msgs/msg/laser_scan.hpp>
+#include <algorithm>
+#include <vector>
+#include <stdexcept>
+#include <limits>
+#include <cmath>
+
+namespace laser_filters
+{
+
+class LaserScanMedianSpatialFilter : public filters::FilterBase<sensor_msgs::msg::LaserScan>
+{
+private:
+  int window_size_;
+
+public:
+
+  bool configure()
+  {
+    getParam("window_size", window_size_);
+
+    // Ensure window size is positive
+    if (window_size_ <= 0)
+    {
+      RCLCPP_ERROR(logging_interface_->get_logger(), "Window size must be positive.\n");
+      return false;
+    }
+
+    // Ensure window size is odd
+    // If the window_size is even, the current range, which will be modified cannot be centered in the window.
+    if (window_size_ % 2 == 0)
+    {
+      RCLCPP_WARN(logging_interface_->get_logger(), "Window size must be odd. Automatically setting window_size to %d instead of %d.\n", window_size_+1, window_size_);
+      window_size_ += 1;
+    }
+
+    return true;
+  }
+
+  virtual ~LaserScanMedianSpatialFilter() {}
+
+  bool update(const sensor_msgs::msg::LaserScan &input_scan, sensor_msgs::msg::LaserScan &filtered_scan)
+  {
+    filtered_scan = input_scan;
+
+    int half_window = window_size_ / 2;
+    std::vector<float> valid_values;
+    int nan_count = 0;
+    int neg_inf_count = 0;
+    int pos_inf_count = 0;
+
+    for (size_t current_beam_index = 0; current_beam_index < input_scan.ranges.size(); ++current_beam_index)
+    {
+        valid_values.clear();
+        nan_count = 0;
+        neg_inf_count = 0;
+        pos_inf_count = 0;
+
+        // Collect points within the window
+        for (int window_offset = -half_window; window_offset <= half_window; ++window_offset)
+        {
+            int index = current_beam_index + window_offset;
+
+            if (index >= 0 && index < input_scan.ranges.size())
+            {
+                float value = input_scan.ranges[index];
+
+                if (std::isnan(value))
+                {
+                    nan_count++;
+                }
+                else if (value == -std::numeric_limits<float>::infinity())
+                {
+                    neg_inf_count++;
+                }
+                else if (value == std::numeric_limits<float>::infinity())
+                {
+                    pos_inf_count++;
+                }
+                else
+                {
+                    valid_values.push_back(value);
+                }
+            }
+        }
+
+        // Determine which set is the largest
+        // In case of a tie, prioritize valid-values over nan-values over neg-inf-values over pos-inf-values
+        if (valid_values.size() >= nan_count && valid_values.size() >= neg_inf_count && valid_values.size() >= pos_inf_count)
+        {
+            // Sort the valid values and return the median
+            std::sort(valid_values.begin(), valid_values.end());
+            filtered_scan.ranges[current_beam_index] = valid_values[valid_values.size() / 2];
+        }
+        else if (nan_count >= valid_values.size() && nan_count >= neg_inf_count && nan_count >= pos_inf_count)
+        {
+            filtered_scan.ranges[current_beam_index] = std::numeric_limits<float>::quiet_NaN();
+        }
+        else if (neg_inf_count >= valid_values.size() && neg_inf_count >= nan_count && neg_inf_count >= pos_inf_count)
+        {
+            filtered_scan.ranges[current_beam_index] = -std::numeric_limits<float>::infinity();
+        }
+        else if (pos_inf_count >= valid_values.size() && pos_inf_count >= nan_count && pos_inf_count >= neg_inf_count)
+        {
+            filtered_scan.ranges[current_beam_index] = std::numeric_limits<float>::infinity();
+        }
+    }
+
+    return true;
+  }
+};
+
+} // namespace laser_filters
+
+#endif // LASER_SCAN_MEDIAN_SPATIAL_FILTER_H

laser_filters_plugins.xml

@@ -60,6 +60,12 @@
 	 This is a filter that removes points on directions defined in a mask from a laser scan.
       </description>
     </class>
+    <class name="laser_filters/LaserScanMedianSpatialFilter" type="laser_filters::LaserScanMedianSpatialFilter" 
+	    base_class_type="filters::FilterBase&lt;sensor_msgs::msg::LaserScan&gt;">
+      <description>
+	This is a spatial 1D median filter which filters sensor_msgs::msg::LaserScan messages. It smoothes continuous obstacles/walls and removes isolated/scattered noise.
+      </description>
+    </class>
     <class name="laser_filters/LaserMedianFilter" type="laser_filters::LaserMedianFilter" 
 	    base_class_type="filters::FilterBase&lt;sensor_msgs::msg::LaserScan&gt;">
       <description>

src/laser_scan_filters.cpp

@@ -28,6 +28,7 @@
  */
 
 #include "laser_filters/median_filter.h"
+#include "laser_filters/median_spatial_filter.h"
 #include "laser_filters/array_filter.h"
 #include "laser_filters/intensity_filter.h"
 #include "laser_filters/range_filter.h"
@@ -46,6 +47,7 @@
 #include <pluginlib/class_list_macros.hpp>  // NOLINT
 
 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::LaserScanIntensityFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)
 PLUGINLIB_EXPORT_CLASS(laser_filters::LaserScanRangeFilter, filters::FilterBase<sensor_msgs::msg::LaserScan>)