From c26293d0004bbd91bb6e50c139ef505bcc4e57d0 Mon Sep 17 00:00:00 2001
From: sl-perception <sl-perception@saltylab.local>
Date: Mon, 2 Mar 2026 11:02:15 -0500
Subject: [PATCH] feat(jetson): depth confidence filter node (issue #190)

Adds depth_confidence_filter_node.py to saltybot_bringup:
- Synchronises /camera/depth/image_rect_raw + /camera/depth/confidence
  via ApproximateTimeSynchronizer (10ms slop)
- Zeros pixels where confidence uint8 < threshold * 255 (default 0.5)
- Republishes filtered float32 depth on /camera/depth/filtered
- Registered as depth_confidence_filter console_scripts entry point

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 .../depth_confidence_filter_node.py           | 96 +++++++++++++++++++
 jetson/ros2_ws/src/saltybot_bringup/setup.py  |  4 +-
 2 files changed, 99 insertions(+), 1 deletion(-)
 create mode 100644 jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/depth_confidence_filter_node.py

diff --git a/jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/depth_confidence_filter_node.py b/jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/depth_confidence_filter_node.py
new file mode 100644
index 0000000..6c56f89
--- /dev/null
+++ b/jetson/ros2_ws/src/saltybot_bringup/saltybot_bringup/depth_confidence_filter_node.py
@@ -0,0 +1,96 @@
+"""
+depth_confidence_filter_node.py — Depth confidence filter for D435i.
+
+Subscribes:
+  /camera/depth/image_rect_raw      sensor_msgs/Image  float32 depth (m)
+  /camera/depth/confidence          sensor_msgs/Image  uint8 confidence (0-255)
+
+Publishes:
+  /camera/depth/filtered            sensor_msgs/Image  float32 depth, low-confidence
+                                                        pixels zeroed
+
+The D435i outputs a per-pixel confidence map alongside the depth image.
+Values below the threshold (default 0.5, normalised from 0–255) are replaced
+with 0.0 (no-return) so downstream nodes (VO, RTAB-Map) treat them as invalid.
+
+Parameters:
+  confidence_threshold  float  0.5    (0.0–1.0; raw uint8 value = threshold * 255)
+  queue_size            int    5
+"""
+
+import rclpy
+from rclpy.node import Node
+from rclpy.qos import QoSProfile, ReliabilityPolicy, HistoryPolicy
+import message_filters
+import numpy as np
+from cv_bridge import CvBridge
+from sensor_msgs.msg import Image
+
+
+_SENSOR_QOS = QoSProfile(
+    reliability=ReliabilityPolicy.BEST_EFFORT,
+    history=HistoryPolicy.KEEP_LAST,
+    depth=5,
+)
+
+
+class DepthConfidenceFilterNode(Node):
+
+    def __init__(self):
+        super().__init__('depth_confidence_filter')
+
+        self.declare_parameter('confidence_threshold', 0.5)
+        self.declare_parameter('queue_size', 5)
+
+        thr_norm   = self.get_parameter('confidence_threshold').value
+        queue_size = self.get_parameter('queue_size').value
+
+        # Raw uint8 threshold (D435i confidence map is 0–255)
+        self._thr = int(thr_norm * 255)
+
+        self._bridge = CvBridge()
+
+        depth_sub = message_filters.Subscriber(
+            self, Image, '/camera/depth/image_rect_raw', qos_profile=_SENSOR_QOS
+        )
+        conf_sub = message_filters.Subscriber(
+            self, Image, '/camera/depth/confidence', qos_profile=_SENSOR_QOS
+        )
+        self._sync = message_filters.ApproximateTimeSynchronizer(
+            [depth_sub, conf_sub], queue_size=queue_size, slop=0.01
+        )
+        self._sync.registerCallback(self._on_frame)
+
+        self._pub = self.create_publisher(Image, '/camera/depth/filtered', 10)
+
+        self.get_logger().info(
+            f'depth_confidence_filter ready — threshold={thr_norm:.2f} ({self._thr}/255)'
+        )
+
+    def _on_frame(self, depth_msg: Image, conf_msg: Image) -> None:
+        try:
+            depth = self._bridge.imgmsg_to_cv2(depth_msg, desired_encoding='32FC1')
+            conf  = self._bridge.imgmsg_to_cv2(conf_msg,  desired_encoding='mono8')
+        except Exception as exc:
+            self.get_logger().warning(f'decode error: {exc}')
+            return
+
+        filtered = np.where(conf >= self._thr, depth, 0.0).astype(np.float32)
+
+        out = self._bridge.cv2_to_imgmsg(filtered, encoding='32FC1')
+        out.header = depth_msg.header
+        self._pub.publish(out)
+
+
+def main(args=None):
+    rclpy.init(args=args)
+    node = DepthConfidenceFilterNode()
+    try:
+        rclpy.spin(node)
+    finally:
+        node.destroy_node()
+        rclpy.shutdown()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/jetson/ros2_ws/src/saltybot_bringup/setup.py b/jetson/ros2_ws/src/saltybot_bringup/setup.py
index 507c836..5c166f5 100644
--- a/jetson/ros2_ws/src/saltybot_bringup/setup.py
+++ b/jetson/ros2_ws/src/saltybot_bringup/setup.py
@@ -27,6 +27,8 @@ setup(
     license='MIT',
     tests_require=['pytest'],
     entry_points={
-        'console_scripts': [],
+        'console_scripts': [
+            'depth_confidence_filter = saltybot_bringup.depth_confidence_filter_node:main',
+        ],
     },
 )
-- 
2.47.2