1. An image processing apparatus, comprising: an input port (IN) for receiving an image (3DV) of an object (HT) acquired at a field of view (FoV) by an imager (USP), the image recording a pose of the object corresponding to the imager's field of view (FoV); a classifier configured to use a geometric model (MOD) of the object (HT) to determine, from a collection of pre-defined poses, the pose of the object as recorded in the image; an output port (OUT) configured to output a pose parameter descriptive of the determined pose, characterized in that the classifier uses a generalized Hough transform, GHT, to determine the object's pose, each of the pre-defined poses associated with a point in the Hough parameter space of the GHT.