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get the raw kinect data

asked 2012-08-28 03:08:20 -0500

ha gravatar image

updated 2012-08-29 03:31:18 -0500

In openni, I think sensor_msgs encode data.

Because, rostopic echo /camera/depth/image and /camera/depth/disparity pulish not 16bit or 11bit, just 0~255.

I think the data is not actual depth data( distance )

I want to know depth value. But I don't know how to get the depth value.

I know the relation ( Z=fT/d ).

I think the fomula substituted raw data is right.

How can I get the raw kinect sensor data?

Or How can I get the actual depth value?

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I think sensor_msgs/image message format is 8bit and using cv_bridge is 16bit or 32bit. Dose from 8bit to 32bit make loss accuracy?

ha gravatar image ha  ( 2012-08-29 11:56:42 -0500 )edit

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answered 2012-08-29 05:37:47 -0500

mjcarroll gravatar image

updated 2012-08-29 05:47:10 -0500

Looking at the openni_camera documentation on the ROS wiki, you can see that the openni_node broadcasts several topics.

I think for the data that you are looking for, the topics of interest will be the depth/image_raw messages, or the depth_registered/image_raw if you have the OpenNI registration turned on.

The */image_raw messages are in the sensor_msgs/Image message format, which stores the data in a byte array, that can then be reassembled in the subscriber. This is accomplished using cv_bridge.

cv_bridge allows you to write code like this for your callback:

void imageCb(const sensor_msgs::ImageConstPtr& msg)
  cv_bridge::CvImagePtr cv_ptr;
    cv_ptr = cv_bridge::toCvCopy(msg, enc::TYPE_32FC1);
  catch (cv_bridge::Exception& e)
    ROS_ERROR("cv_bridge exception: %s", e.what());
  cv::imshow(WINDOW, cv_ptr->image);

cv_ptr->image will contain an OpenCV cv::Mat, in this case containing floating point values, which represent the depth in millimeters for that pixel.

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Can you tell how to access the floating point values in cv_ptr->image?

shinnqy gravatar image shinnqy  ( 2014-05-21 22:59:25 -0500 )edit

answered 2012-08-28 05:09:40 -0500

hahaha gravatar image

I also read the page (

" The raw 11-bit disparity value to a depth value in centimeters is:

100/(-0.00307 * rawDisparity + 3.33). "

  1. depth value = distance. Is it right?

  2. So, how can I get the rawDisparity?

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Please do not create answers just for discussing or asking new questions. This is not a forum. Instead please either use comments or (if you are the original poster) edit the question.

Lorenz gravatar image Lorenz  ( 2012-08-29 03:48:49 -0500 )edit

I am sorry~ but I don't find "add comment" in windows. How can I find it. I use ros in ubuntu now. And can you answer my former question? please

hahaha gravatar image hahaha  ( 2012-08-29 04:52:00 -0500 )edit

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Asked: 2012-08-28 03:08:20 -0500

Seen: 2,821 times

Last updated: Aug 29 '12