Hardcopy hologram watermarking based on discrete wavelet transform

A hardcopy digital hologram watermarking method based on discrete wavelet transform is proposed. First, the watermark was converted to a digital hologram using the computer-generated holography by the conjugate-symmetric extension. The host image and the hologram were then decomposed with discrete wavelet transform. High frequency components of the hologram were embedded into intermediate frequency components of the host image. Because of the adjustable spectrum and the tearing-resistance of the hologram, the blind extraction of the watermark can be achieved. The watermark is robust against cropping, noise contamination, filtering, and JPEG compression. Particularly, the watermark can be extracted from the scanned version of a printed hardcopy of the watermarked image.