1. An image processing apparatus comprising: a segmenting unit that segments an image into regions each having connected pixels; a representative-point setting unit that sets a representative point representing each of the regions segmented by the segmenting unit; a vector calculating unit that calculates vectors, each constituted of two representative points, on the basis of the representative points set by the representative-point setting unit; and a screen-ruling-and-angle extracting unit that extracts screen ruling and a screen angle used in the image on the basis of distribution of the vectors calculated by the vector calculating unit.