An image, represented by an ordered set of elements (xi) each having a value is analysed in order to detect vanishing points. The method comprises, for each of a plurality of root positions (x0), repeatedly performing the steps of: (i) selecting a first plurality of elements (xi) from the ordered set; (ii) for each selected element (xi), selecting a second element (ui) such that the selected second element has a vector position relative to the root position that is scaled by a factor (α) in comparison with the position of the first selected element; (iii) determining whether the selected elements meet a match criterion requiring that the value of each of the first elements is similar to the value of the corresponding second element; and (iv) in the event of a match, updating a similarity score (H) in respect of that root element. Once these scores have been found, they can be examined a part of the image corresponding to a peak value of the similarity score.