Hi Debjyoti

I'm not quite sure that I understand your question, so here are two possible
alternatives:
1. If you want to associate points in the 3D cloud with real pixels in the
image, look at the points2 message (of type PointCloud2) that
stereo_image_proc publishes. The points in the points2 message are arranged
in an array that corresponds to the original image array, so points[x][y]
corresponds to image[x][y].
2. If you want to project a new point in space onto the image, look at the
image_geometry package (http://www.ros.org/wiki/image_geometry).

Hope that helps
-Caroline

On Fri, Oct 8, 2010 at 2:34 AM, Bera, D. <d.bera@tue.nl> wrote:

> Dear all,
>
> At this moment, we are working with a standard Videre stereo camera and
> make use of standard nodes available from ROS repositories to publish a
> dense point cloud (stereo_image_proc: node).  It would be of great help if
> we could have some suggestions on how to correlate a point on a 2D stereo
> images to a 3D point in a point cloud? Do we need to make a new node to
> perform this operation? What would be its feasibility, accuracy?
>
> Thanks and Regards,
> Debjyoti Bera.
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