A method (200) is disclosed of detecting one or more patterns embedded in an image. Each pattern embedded in the image has been formed from a one-dimensional basis function. The method (200) starts by calculating (210) a projective transform of the image. A 1-D correlation is then calculated (220) between the projective transform and the basis function for a selection of angles. Finally, one or more peaks of the correlation are found (230). The position of each of the peaks provides spatial parameters of one of the one or more embedded patterns.