| 摘要 |
The present invention relates to a hologram watermarking method based on a Fresnel diffraction model, which is to process a digital hologram to generate a diffraction pattern in a two-dimensional (2D) form by using Fresnel transformation, to perform the Fresnel transformation again on the hologram so as to generate a watermark area around an image, and to insert the watermark undergone the Fresnel transformation into the watermark area and extract the same. The hologram watermarking method comprises the steps of: (a) obtaining a complex image by applying Fresnel transformation to a digital hologram image; (b) transforming the complex image into a polar-form image, and generating a magnitude image in a 2D form consisting of magnitude components in the polar-form image; (c) applying the Fresnel transformation to the magnitude image so as to obtain an transformed image; (d) inserting a watermark into the transformed magnitude image; (e) performing inverse Fresnel transformation on the transformed magnitude image into which the watermark is inserted so as to restore the magnitude image; (f) reconstituting the polar-form image with the restored magnitude image and transforming the polar-form image reconstituted into the complex image so as to restore the image; and (g) restoring the complex image restored to a digital hologram image via inverse Fresnel transformation so as to obtain a hologram image into which the watermark is inserted. By the hologram watermarking method stated above, the watermark insertion area is inserted after being enlarged to surrounding areas using Fresnel transformation properties, thus the inserted watermark can have enough invisibility and be resilient against general image-processing attacks such as Gaussian blur, sharpening, image compression and the like. |
