Image analysis relating to extracting three dimensional information from a two dimensional image

A method of analysing an image represented by an ordered set of elements (xi) each having a value, the method comprising, for each of a plurality of reference directions, repeatedly performing the steps of:

• selecting a first plurality of elements (xi) from the ordered set;
• for each selected element (xi), selecting a second element (ui) such that the selected second element has a position that is, in comparison with the position of the first selected element, shifted in the respective reference direction by a shift amount (Δ);
• determining, using a computer system having at least one processor, 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;
• in the event of a match between the two selected elements, updating a similarity score (H) in respect of that reference direction;
• and
• selecting at least one of the plurality of reference directions as an indication of the direction of a vanishing point of the image at infinity wherein the at least one selected reference direction is associated with a peak in the similarity scores (H).