Digital image coding/decoding apparatus and method for recording and restoring a signature image using watermarking

摘要

Digital image encoding/decoding apparatus and methods for recording a signature image using watermarking, and for restoring the recorded signature image are provided. The digital image coding apparatus for recording a signature image on a host image using watermarking, includes a first discrete wavelet transform portion for receiving a host image and performing discrete wavelet transform thereon, thereby outputting M×M discrete wavelet coefficients where M is a predetermined positive integer, a second discrete wavelet transform portion for receiving a signature image and performing discrete wavelet transform thereon, thereby outputting N×N discrete wavelet coefficients, where N is a predetermined positive integer smaller than M, a pseudo-random number generator for receiving an encryption code for determining a predetermined rule for generating pseudo-random numbers and generating the pseudo-random numbers in accordance with the predetermined rule corresponding to the encryption code, and a coefficient replacement portion for selecting the replacing locations of N×N pixels using the pseudo-random numbers, and replacing the coefficients of the selected N×N pixel locations among M×M discrete wavelet coefficients with N×N wavelet coefficients, thereby outputting replaced M×M wavelet coefficients. Since transmission is made such that a portion of signature image coefficients is superimposed on that of host image coefficients. Thus, addition of signature image coefficients does not increase the amount of transmitted data.