1. An image processing apparatus that encodes a document image including a non-photo image region, the apparatus comprising: a region identify unit adapted to perform region separation on a document image and identify a non-photo image region; a first encoder adapted to encode the non-photo image region through a vectorization process; a background identify unit adapted to identify a background region from the non-photo image region; a filling unit adapted to fill a region other than the background region of the non-photo image region with a color of the background region; and a second encoder adapted to encode the document image after the region other than the background region of the non-photo image region has been filled by said filling unit, through an image compressing process.