In view of the fact that many watermarking schemes cannot well adapt to the occasion of image copyright protection with a large amount of information, and the copyright protection of color image is facing severe challenges, a dual-color image watermarking scheme based on URV decomposition (URVD) and image correction is designed in this paper. The two-dimensional Logistic-adjusted-Sine map is first used to generate two chaotic sequences for pixel-level scrambling and bit-level diffusion of the watermark image, and URVD is applied to watermarking scheme. After fully considering the relationship between image channels, the watermark is embedded into the maximum URVD coefficient by using quantization index modulation based on variable quantization steps. The greatest contribution of this paper is to propose a new image correction algorithm as a pretreatment of watermark extraction, which mainly includes fast detection of feature points, image correction, and sawtooth processing, and it solves some problems existing in image correction algorithms based on geometric characteristics. Experimental results show that the proposed scheme has good invisibility, strong robustness, and high security. Compared with existing schemes, the proposed scheme has better performance under the same actual embedding rate, especially stronger and more effective robustness against some common geometric attacks.

It has great significance for protecting the image copyright with color image digital watermarking technique, which needs the watermarking algorithm has high robustness, good imperceptibility and short running-time. A blind colour image watermarking algorithm combined spatial domain and singular value decomposition (SVD) is designed to protect the rightful ownership of color image in this paper. The theoretical principle combined SVD and spatial domain is first discussed and proposed in this paper. Based on the derived principle, the watermark information can be directly embedded into the maximum singular value (MSV) of the host image in the spatial domain by the new quantization index modulation with variable quantization step, and the embedded watermark information can be directly extracted from the MSV of the watermarked image block in the spatial domain with geometrical correction. The contributions of this paper include the following four points: (1) the relationship between the changed MSV of SVD and the average changed value of image pixel in the spatial domain is the first derived in this paper; (2) the presented method has the merits of both spatial-domain technique and transform-domain technique; (3) the relationships of each component of the color image are used to improve the invisibility and the geometrical correction of watermarked image is also adapted to further improve the robustness; and (4) this presented method overcomes the false-positive problem that existed in many watermarking methods based on SVD. Simulation results demonstrate the new presented color image watermarking technique has better imperceptibility, higher robustness and shorter running-time compared with some state-of-the-art methods.

In this paper, a spatial domain-based blind watermarking scheme of color images integrating multilevel discrete Hartley transform (DHT) is proposed to protect color digital images' copyright under the current 5G network environment. On the basis of the unique spatial computing property of the maximum energy coefficient of DHT and the energy aggregation principle of multilevel image transform, the color watermark image scrambled by Affine transform is directly hidden into color carrier image by quantitative techniques in the spatial domain, rather than the complex DHT domain. The specific performance of the scheme in various aspects is as follows: (1) the average value of the peak signal-to-noise ratio is higher than 40 dB; (2) the average value of structural similarity index metric remains above 0.9700; (3) the average value of normalized cross-correlation under no attack is 1.0000; (4) the average value of normalized cross-correlation. under attack is above 0.9600; (5) the total execution time is 1.1856 s; (6) the maximum embedding capacity is 0.0625 bpp; and (7) the entire key space is greater than 2432. Multiple simulation results demonstrate that the proposed scheme is not merely imperceptible and robust, but also secure and efficient, which can protect the digital copyright with effect.