1. An image processing apparatus comprising: an image acquisition unit that acquires a first image and a second image, each of the images including a character string; an extraction unit that extracts feature points included in each of the first image and the second image; a setting unit that sets, in each of the first image and the second image, at least one partial region including a plurality of characters that are continuously arranged in an arrangement direction of the character string; and a specification unit that compares positions of the feature points included in the at least one partial region set in the first image by the setting unit with positions of the feature points included in the at least one partial region set in the second image by the setting unit so as to specify at least one said at least one partial region set in the second image that corresponds to at least one said at least one partial region set in the first image, and to specify corresponding feature points in each of the specified partial regions.