1. An image processing apparatus comprising: a feature point extraction unit that extracts feature points which are pixels located at the corner of a region within an image and directions indicating a positional relationship of the feature points in the region; a selection unit that selects the feature point and a set of feature points corresponding to the feature point, on the basis of a color of the feature point extracted by the feature point extraction unit, a position of the feature point, and a direction in the feature point; a representative point determination unit that determines a representative point representing a region, on the basis of the set of feature points selected by the selection unit; a vector calculation unit that calculates a vector composed of two representative points, on the basis of the representative points determined by the representative point determination unit; and a screen line number and angle extraction unit that extracts the number of screen lines and an angle used in the image, on the basis of a distribution of the vectors calculated by the vector calculation unit.