Method and device for embedding and extracting digital watermarking

Abstract

The invention discloses a method and device for embedding and extracting digital watermarking. The method comprises the steps of: conducting discrete cosine transform (DCT) to a low-frequency area obtained by generating a CDMA (Code Division Multiple Access) watermarking sequence and carrying out discrete wavelet transform (DWT) to a host image; embedding the CDMA watermarking sequence into a medium-high frequency DCT coefficient sequence determined by a secret key. No color loss can be ensured in color mode translation by embedding watermarking in the LAB color space of the image, the robustness and invisibility of the watermarking can be improved by adding watermarking onto the DWT and DCT transformed coefficient of the image, and the capacity of the watermarking can be increased through the CDMA coding technique.

Description

technical field [0001] The invention relates to the technical field of digital image processing, in particular to a method and device for embedding and extracting a digital watermark. Background technique [0002] The digital watermark used for ticket anti-counterfeiting needs to embed the watermark in the original image of the ticket, so that when the ticket is printed, the watermark is also included in the paper ticket. When it is necessary to check the authenticity of the paper bill, it is necessary to scan the paper bill, and then extract the correct watermark from the scanned bill image. The robustness and fragility of this watermark is therefore mainly linked to the distortion it introduces during printing and scanning. In the process of printing and scanning, image distortion mainly comes down to three categories: one is the distortion of image pixels, which mainly includes the change of brightness contrast, halftone of image, color change, point diffusion, point det...

AI Technical Summary

Problems solved by technology

[0004] Embed the watermark in the space domain, generally the length of the embedded watermark is short, and the resistance to attack is poor

And because the watermark is embedded in RGB space or YIQ space, in the process of printing and scanning, because the image has different color space description methods on different devices, it is easy to cause image distortion, resulting in failure of watermark extraction

However, the digital watermark in the DCT domain is not robust to JPEG2000 compression, and if the digital watermark in the DWT domain is directly embedded in the low-frequency domain of the wavelet domain, it will easily cause mosaic phenomenon in the image after the watermark is embedded. If the domain is embedded, although the watermark is not visible, the robustness of the watermark is low

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