1. An image processing apparatus for achieving the exchange of pieces of image data between a plurality of image processing apparatuses, comprising: a feature value extraction unit configured to extract a feature value included in image data; a feature value transfer unit configured to transfer to another image processing apparatus a feature value extracted from image data to be exchanged; a feature value reception unit configured to receive a feature value transferred from the other image processing apparatus; a first determination unit configured to determine whether the received feature value matches a feature value included in image data of a captured image; an image data transfer unit configured to transfer the image data of the captured image to the other image processing apparatus when there is a match between the feature values; and an image data reception unit configured to receive image data of a captured image transferred from the other image processing apparatus.