1. An image processing apparatus comprising: an image area separation device configured to separate input image data into image data and image area separation data; a compression device configured to compress the image data in accordance with a given compression method; an image storage device configured to store the compressed image data; an image area storage device configured to store the image area separation data; a data writing device configured to write the image area separation data to the image area storage device, secure an initial compressed image storage region of a predetermined data size in the image storage device, and sequentially store the compressed image data in the initial compressed image storage region; and an image output state monitoring device configured to monitor a compressed image data amount, and cause the data writing device to secure an additional storage region in the image storage device upon determination that the compressed image data amount has reached or exceeded a data amount storable in the initial compressed image storage region.