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New in ROS Fuerte depth_image_proc has found a new home in image_pipeline. In Electric it resided in openni_kinect.

Overview

depth_image_proc provides basic processing for depth images, much as image_proc does for traditional 2D images. The two packages are complementary; for example, you can (and should!) rectify your depth image before converting it to a point cloud.

A variety of camera technologies can produce depth images:

• The Kinect and related devices

• Traditional stereo cameras
• Time-of-flight cameras

See REP 118 for details on depth image representation. The REP recommends that, wherever possible, producers and consumers of depth data use depth images (of type sensor_msgs/Image) instead of sensor_msgs/DisparityImage.

All nodelets (besides convert_metric) in this package support both standard floating point depth images and OpenNI-specific uint16 depth images. Thus when working with OpenNI cameras (e.g. the Kinect), you can save a few CPU cycles by using the uint16 raw topics instead of the float topics.

For an example of depth_image_proc in practice, examine the contents of openni_launch.

Nodelets

depth_image_proc/convert_metric

Nodelet to convert raw uint16 depth image in mm to float depth image in m.

Subscribed Topics

image_raw (sensor_msgs/Image)

• uint16 depth image in mm, the native OpenNI format.

Published Topics

image (sensor_msgs/Image)

• float depth image in m, the recommended format for processing in ROS.

depth_image_proc/disparity

Nodelet to convert depth image to disparity image.

Subscribed Topics

left/image_rect (sensor_msgs/Image)

• Rectified depth image.

right/camera_info (sensor_msgs/CameraInfo)

• Camera calibration and metadata. Must contain the baseline, which conventionally is encoded in the right camera P matrix.

Published Topics

left/disparity (stereo_msgs/DisparityImage)

• Disparity image (inversely related to depth), for interop with stereo processing nodes. For all other purposes use depth images instead.

Parameters

min_range (double, default: 0.0)

• Minimum detectable distance.

max_range (double, default: +Inf)

• Maximum detectable distance.

delta_d (double, default: 0.125)

• Smallest allowed disparity increment, which relates to the achievable depth range resolution. Defaults to 1/8 pixel.

queue_size (int, default: 5)

• Size of message queue for synchronizing subscribed topics.

depth_image_proc/point_cloud_xyz

Nodelet to convert depth image to XYZ point cloud.

Subscribed Topics

camera_info (sensor_msgs/CameraInfo)

• Camera calibration and metadata.

image_rect (sensor_msgs/Image)

• Rectified depth image.

Published Topics

points (sensor_msgs/PointCloud2)

• XYZ point cloud. If using PCL, subscribe as PointCloud<PointXYZ>.

Parameters

queue_size (int, default: 5)

• Size of message queue for synchronizing subscribed topics.

depth_image_proc/point_cloud_xyzrgb

Nodelet to combine registered depth image and RGB image into XYZRGB point cloud.

Subscribed Topics

rgb/camera_info (sensor_msgs/CameraInfo)

• Camera calibration and metadata.

rgb/image_rect_color (sensor_msgs/Image)

• Rectified color image.

depth_registered/image_rect (sensor_msgs/Image)

• Rectified depth image, registered to the RGB camera.

Published Topics

depth_registered/points (sensor_msgs/PointCloud2)

• XYZRGB point cloud. If using PCL, subscribe as PointCloud<PointXYZRGB>.

Parameters

queue_size (int, default: 5)

• Size of message queue for synchronizing subscribed topics.

depth_image_proc/register

Nodelet to "register" a depth image to another camera frame. Reprojecting the depths requires the calibration parameters of both cameras and, from tf, the extrinsic transform between them.

Subscribed Topics

rgb/camera_info (sensor_msgs/CameraInfo)

• RGB camera calibration and metadata.

depth/camera_info (sensor_msgs/CameraInfo)

• Depth camera calibration and metadata.

depth/image_rect (sensor_msgs/Image)

• Rectified depth image.

Published Topics

depth_registered/camera_info (sensor_msgs/CameraInfo)

• Camera calibration and metadata. Same as rgb/camera_info but time-synced to depth_registered/image_rect.

depth_registered/image_rect (sensor_msgs/Image)

• Reprojected depth image in the RGB camera frame.

Parameters

queue_size (int, default: 5)

• Size of message queue for synchronizing subscribed topics.

Required tf Transforms

/depth_optical_frame → /rgb_optical_frame

• The transform between the depth and RGB camera optical frames as specified in the headers of the subscribed topics (rendered here as /depth_optical_frame and /rgb_optical_frame).

Execution

Since the package is made of 'nodelet's, 'nodelet' execution method is used as: http://wiki.ros.org/nodelet/Tutorials/Running%20a%20nodelet

For example, the launch file to execute a 'point_cloud_xyz' nodelet is like as:

<launch>
  <node pkg="nodelet" type="nodelet" name="nodelet_manager" args="manager" />

  <node pkg="nodelet" type="nodelet" name="nodelet1"
        args="load depth_image_proc/point_cloud_xyz nodelet_manager">
    <remap from="camera_info" to="/camera/depth/camera_info"/>
    <remap from="image_rect" to="/camera/depth/image_rect_raw"/>
    <remap from="points" to="/camera/depth/points"/>
  </node>
</launch>