17. The computer storage medium of claim 16 , wherein the plurality of image lines includes a plurality of vertical linelets and a plurality of horizontal linelets, each vertical linelet being a skeletal line through an upright portion of a connected component, each horizontal linelet being a regression line through a center of a set of adjacent connected components.
17. The computer storage medium of claim 16 , wherein the plurality of image lines includes a plurality of vertical linelets and a plurality of horizontal linelets, each vertical linelet being a skeletal line through an upright portion of a connected component, each horizontal linelet being a regression line through a center of a set of adjacent connected components. 18. The computer storage medium of claim 17 , wherein calculating a horizontal vanishing point and a vertical vanishing point based on the plurality of image lines further comprises: calculating the horizontal vanishing point using the horizontal linelets; and calculating the vertical vanishing point using the vertical linelets.