An apparatus for storing digital images has a storage device for storing a
current reference image and a plurality of differential images, and an
image processing device coupled to the storage device. The image
processing device receives an individual digital image, determines a
difference between the individual image and the current reference image,
and stores this difference as a differential image in the storage device.
The apparatus also has reference image updating means for determining when
to generate a new reference image, for generating the new reference image,
for replacing the current reference image with the new reference image,
and for storing the new reference image as current reference image in the
storage device.
