Hi.

I appreciate all the efforts and amazing work in the ROS community. In my situation, I am trying to estimate a distance to an object using RTABMap, ROS, and a Kinect 360. For my implementation, we are using ROS indigo and libfreenect .

In our system, we are able to display the field of view of the robot to a web page using roslibjs. When the user clicks on a certain (x,y) coordinate on that video stream, we want to obtain an estimated distance to the object.

Is there an API in RTABMap/ROS that can help me obtain this information easily?

It looks like the information should be available in the following topic: /camera/depthregistered/imageraw - Raw image from device. Contains uint16 depths in mm.

I'm not sure how I might extract/read the information.

I do appreciate your help and pointers.

All the best!

void callback(
    const sensor_msgs::ImageConstPtr& depth,
    const sensor_msgs::CameraInfoConstPtr& cameraInfo)
{
    cv_bridge::CvImageConstPtr ptr = cv_bridge::toCvShare(depth);

    float distance = 0.0f; // meters
    if(image.type() == CV_32FC1)
    {
        distance = ptr->image.at<float>(y, x);
    }
    else // CV_16UC1
    {
        distance = ptr->image.at<unsigned short>(y, x)/1000.0f; // convert from mm to meters
    }
    ...

image_geometry::PinholeCameraModel model;
model.fromCameraInfo(cameraInfo);
cv::Point3d ray = model.projectPixelTo3dRay(cv::Point2d(x,y));
cv::Point3d pt3d = ray * distance;