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image_cache

The image cache node holds a central position in our architecture and serves multiple purposes detailed above.

Subscribed Topics

left/image_raw (sensor_msgs/Image)

• Raw image stream from the left camera

left/camera_info (sensor_msgs/CameraInfo)

• Left camera metadata

right/image_raw (sensor_msgs/Image)

• Raw image stream from the right camera

right/camera_info (sensor_msgs/CameraInfo)

• Right camera metadata

node_added (slam_backend/NodeAdded)

• Timestamp and Node ID of vertex newly added to the graph

Published Topics

throttled_image_raw (sensor_msgs/Image)

• Republished left image sampled at sub frame rate

Services

image_service (image_cache/GetImage)

• Request any number of to images specified as matching a given from image using this service. The caller node should specify IDs in republished space, and is also required to specify whether the return images should be rectified or not. The service returns the stereo image pairs for the from image and for all to images.

info_service (image_cache/GetInfo)

• Request stored camera information via this service.

neighbour_service (image_cache/GetNeighbours)

• Request the neighbours in the SLAM graph corresponding to a particular republished image ID. This information is then used to insert loop closure edges at interpolated points in the graph.

Parameters

~stereo_topic (string, default: stereo)

• The topic prefix under which stereo images are published.

~republished_topic (string, default: throttled)

• The topic prefix under which the republished image should be published.

~cache_path (string, default: ./)

• The directory location at which the image cache should be stored.

~div (int, default: 4)

• The rate at which to subsample images. By default, republish and save every fourth image.