Spatial median filter

include/laser_filters/median_spatial_filter.h

@@ -0,0 +1,122 @@
+/*********************************************************************
+* 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>
+
+namespace laser_filters
+{
+
+class LaserScanMedianSpatialFilter : public filters::FilterBase<sensor_msgs::msg::LaserScan>
+{
+public:
+  int window_size_;
+
+  bool configure()
+  {
+    // Default window size
+    window_size_ = 3;
+    getParam("window_size", window_size_);
+
+    // Ensure window size is positive
+    if (window_size_ <= 0)
+    {
+      throw std::runtime_error("Window size must be positive");
+    }
+
+    // Ensure window size is odd
+    if (window_size_ % 2 == 0)
+    {
+      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> window;
+
+    for (size_t i = 0; i < input_scan.ranges.size(); ++i)
+    {
+      window.clear();
+
+      // Collect points within the window
+      for (int j = -half_window; j <= half_window; ++j)
+      {
+        int index = i + j;
+
+        if (index >= 0 && index < input_scan.ranges.size())
+        {
+          if (!std::isnan(input_scan.ranges[index]))
+          {
+            window.push_back(input_scan.ranges[index]);
+          }
+        }
+      }
+
+      if (!window.empty())
+      {
+        // Calculate median
+        std::sort(window.begin(), window.end());
+        filtered_scan.ranges[i] = window[window.size() / 2];
+      }
+      else
+      {
+        filtered_scan.ranges[i] = std::numeric_limits<float>::quiet_NaN();
+      }
+    }
+
+    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.  
+      </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>)