Re-distort points with camera intrinsics/extrinsics

Question

Given a set of 2D points, how can I apply the opposite of undistortPoints?

I have the camera intrinsics and distCoeffs and would like to (for example) create a square, and distort it as if the camera had viewed it through the lens.

I have found a 'distort' patch here : http://code.opencv.org/issues/1387 but it would seem this is only good for images, I want to work on sparse points.

Answer 1

This question is rather old but since I ended up here from a google search without seeing a neat answer I decided to answer it anyway.

There is a function called projectPoints that does exactly this. The C version is used internally by OpenCV when estimating camera parameters with functions like calibrateCamera and stereoCalibrate

EDIT:
To use 2D points as input, we can set all z-coordinates to 1 with convertPointsToHomogeneous and use projectPoints with no rotation and no translation.

cv::Mat points2d = ...;
cv::Mat points3d;
cv::Mat distorted_points2d;
convertPointsToHomogeneous(points2d, points3d);
projectPoints(points3d, cv::Vec3f(0,0,0), cv::Vec3f(0,0,0), camera_matrix, dist_coeffs, distorted_points2d);