Function to get detected keypoint indices in PCL keypoint detectors

[musi00]

PCL currently does not provide an interface to get the indices of the detected keypoints using a keypoint detector such as ISSKeypoint3D. For example if I have situation where I have pointcloud and its associated normals pointcloud and I wanted to detect the keypoints of that cloud and get the normals associated with those keypoints. To get the normals of the cloud using the pcl implementation you would have to rerun the normal estimation for the keypoints which is a waste of processing because the normals are already there in the original normals cloud. Having the indices of the keypoints would allow me to simply access those indices in the normals cloud in constant time.

[musi00]

@nizar-sallem I created the issue but I don't think I have rights to assign it to anybody or tag it

[nizar-sallem]

it is ok :)

[nizar-sallem]

Work is in progress, the keypoint indices will be stored in the label field if any.
So for instance instead of calling pcl::HarrisKeypoint3D <pcl::PointXYZRGB, pcl::PointXYZRGB> you will need to call pcl::HarrisKeypoint3D <pcl::PointXYZRGB, pcl::PointXYZRGBL> and then get the indices from the label field of each point. I will wait for the ISSKeypoint bug fix to be pulled before asking for the pull request.

[nizar-sallem]

I had a change of heart, a better way to do it is to provide keypoints indices through a getKeypointsIndices () method.