1. An apparatus having an image processing function, comprising: first acquisition means for acquiring a first portion of data as a data stream obtained from image data that has been sequentially converted and encoded; decoding means for decoding the data acquired by said first acquisition means and obtaining a two-dimensional image; analysis means for analyzing the two-dimensional image obtained by said decoding means and determining a region of interest within the two-dimensional image; and second acquisition means for acquiring a second portion of data as a data stream obtained from the image data based on the region of interest determined by said analysis means.