An image processing apparatus includes a geometric position obtaining unit, an image retrieving unit, and an image rectifying unit. The geometric position obtaining unit receives a geometric transformation parameter, a block size, and a tile size, obtains a plurality of base-point coordinates of the geometric transformation parameter according to the block size and the tile size, and builds a base-point coordinate table according to the base-point coordinates. The image retrieving unit reads the base-point coordinate table, scans the base-point coordinate table according a fixed block size to generate a plurality of reference image ranges, and respectively retrieves a plurality of partial image data of a to-be-processed image data according to each of the reference image ranges. The image rectifying unit rectifies each of the partial image data according to the geometric transformation parameter.