RANSAC and 2D point clouds

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but we must have pair point in vectors firstPtVector, secndPtVector isn't it? I have just 2 point sets without pairs.

If you do not have pairing, you cannot define anything. There are infinite combinations of possibilities of transforms between two points sets.

I don't fink so, for example http://www.mrpt.org/Iterative_Closest_Point_(ICP)_and_other_matching_algorithms I just don't know how to generalize ICP algorithm to perspective transform.

@sammy , under some constraints (you know the relation is an affine transform for example), in most real world cases there is only one transform.

I need to align raster and vector data, raster data is distorted, I represent the, as point clouds in 2D. Look here there is no need for pair points http://www.mrpt.org/Iterative_Closest_Point_(ICP)_and_other_matching_algorithms but I need non rigid ICP.

If distortion is not too big you may still use ICP. ICP doesn't require that 2 point clouds are exactly identical. One point cloud may contain points corrupted with a noise and ICP will still work.

The catch is that ICP requires point clouds to be roughly aligned. So if corresponding points in your point clouds are quite close you may use ICP. Otherwise you'll need to use some method to roughly align your point clouds (e.g. compute some kind of feature descriptors for each point, use these feature descriptors to create matching between points in both clouds and roughly align point clouds using these matchings) and then use ICP for final registration.

The problem is that implementation of ICP that I found have only translate and rotation invariance, but I need to register images with perspective transform.