camera_preprocessing

camera_preprocessing.py

Overview

camera_preprocessing.py is a horizontal (domain-independent) data-filter component that improves raw RGB + depth imagery before any perception or fusion module touches it. Every robot sharing the same message contracts can reuse this node as-is, giving you a single place to tweak sensor quirks instead of a dozen ad-hoc patches spread across your stack.

Interfaces (strongly-typed, stateless)

Direction

Topic

Message type

Notes

Required

/{robot}/camera

sensor_msgs/Image

BGR8 frames

Required

/{robot}/depth

sensor_msgs/Image

Any depth encoding

Provided

/{robot}/camera_processed

sensor_msgs/Image

Same header; 5 × 5 Gaussian blur (σ ≈ 1)

Provided

/{robot}/depth_processed

sensor_msgs/Image

Same header; values < 0.5 m set to 0

Contract

Pre-conditions

  • Incoming RGB must be 8-bit, 3-channel (BGR8).

  • Depth resolution not larger than 1920×1080 (soft real-time ceiling).

Post-conditions

  • Header stamp and frame_id are identical between input and output.

  • Latency from callback entry to publish is < 12 ms on a 4-core laptop.

  • Output resolution equals input (no accidental rescale).

Invariants

  • Peak RAM ≤ 5×(w×h×c) bytes (one temp copy plus output buffer).

Protocol

  1. Subscribe to both raw topics.

  2. Publish processed counterparts for every incoming frame.

  3. No service calls or stateful dialogue; each message is handled independently.

Lifecycle

  • Node name: {robot}_camera_preprocessing_node.

  • Ready when its two publishers are advertised (no extra init service).

  • Clean shutdown on Ctrl-C or rosnode kill, handled by rospy.

Quality & Reusability Metrics

  • Latency < 12 ms → supports 30 Hz pipelines.

  • Throughput ≥ camera frame-rate (default 30 Hz).

  • Cyclomatic complexity < 15 → easy to maintain / extend.

Adding such a server is orthogonal to the current contract and does not break existing clients.

Implementation Notes

  • A single global CvBridge keeps conversion overhead low.

  • Processing occurs inside subscriber callbacks (no poll loop).

  • The duplicate publisher block at the end of __init__ preserves existing downstream contracts; remove it only after all consumers migrate to the namespaced topics.

Classes

CameraPreprocessing()

In-place enhancement for RGB and depth streams.