This invention provides a technique capable of always keeping digital
watermark information embedded in image data having the embedded digital
watermark information by an optimum scheme on the basis of a time factor,
or removing a digital watermark, or erasing the image data. An apparatus
for achieving the above object has functions of holding image data having
additional information embedded as a digital watermark, detecting time
information related to the image data, and changing the embedding scheme
for the additional information as the digital watermark embedded in the
image data on the basis of the detected time information.
