| 摘要 |
THE PRESENT INVENTION RELATES TO A DIGITAL IMAGE WATERMARKING APPARATUS AND METHOD. ACCORDING TO THE PRESENT INVENTION, LUMINANCE COMPONENTS OF A DIGITAL IMAGE ARE TRANSFORMED INTO THE COEFFICIENT OF A FREQUENCY DOMAIN, AND WATERMARK IS GENERATED BY ENCRYPTING A USER KEY AND GENERATING PSEUDO RANDOM NUMBER. THEN, A REPLACEMENT COEFFICIENT GENERATED BY USING THE COEFFICIENT OF A FIRST FREQUENCY DOMAIN AMONG THE COEFFICIENTS OF THE FREQUENCY DOMAIN AND SAID WATERMARK IS SUBSTITUTED WITH THE COEFFICIENT OF A SECOND FREQUENCY DOMAIN SO THAT THE WATERMARK IS EMBEDDED INTO THE DIGITAL IMAGE. THE EMBEDDED WATERMARK IS EXTRACTED AT AN AUTHENTICATING APPARATUS AND THE DIGITAL IMAGE IS AUTHENTICATED BY FINDING THE CORRELATION BETWEEN THE EXTRACTED WATERMARK AND WATERMARK FOR AUTHENTICATION. THUS, IT IS POSSIBLE TO EXTRACT WATERMARK WITHOUT USING ORIGINAL IMAGE, PROVIDING THE WATERMARK ROBUST TO PRINTING OR VARIOUS IMAGE TRANSFORM AND WHICH DOES NOT DETERIORATE THE QUALITY OF THE DIGITAL IMAGE. (FIG. 1) |
