Patent ID: 7269272

Claim:
An image processing apparatus which converts multilevel image data into frequency component data for each pixel block of a predetermined size to compression-code the multilevel image data, and multiplexes noise on the multilevel image to embed visible additional information with a noise-multiplexed distribution, comprising: input means for inputting, as the additional information, information representing whether or not to multiplex noise for each pixel block or the predetermined size; determination means for determining on the basis of the input additional information whether a pixel block of interest is located at a position where noise is to be multiplexed; specifying means for, when said determination means determines that the pixel block of interest is located at the position where noise is to be multiplexed, specifying a bit region where noise is to be multiplexed in data constituting a converted low frequency component of the pixel block of interest on the basis of a reference region serving as a converted low frequency component of a neighboring pixel block near the pixel block of interest; and change means for reversibly changing bit information for the bit region in the data of the low frequency component specified by said specifying means.