1. An image processing apparatus comprising: a geometric position obtaining unit receiving a geometric transformation parameter, a block size, and a tile size, obtaining a plurality of base-point coordinates of the geometric transformation parameter according to the block size and the tile size, and building a base-point coordinate table according to the base-point coordinates, wherein, each of a plurality of base-points is one point of each of the blocks in a tile; an image retrieving unit coupled to the geometric position obtaining unit, the image retrieving unit reading the base-point coordinate table, scanning the base-point coordinate table according a fixed block size to generate a plurality of reference image ranges, and respectively retrieving a plurality of partial image data of a to-be-processed image data according to each of the reference image ranges; and an image rectifying unit coupled to the image retrieving unit and the geometric position obtaining unit, the image rectifying unit rectifying each of the partial image data according to the geometric transformation parameter.