Shao Hua Li

Bio: Shao Hua Li is an academic researcher from Dalian University of Foreign Languages. The author has contributed to research in topics: Digital watermarking & Image processing. The author has an hindex of 1, co-authored 2 publications receiving 10 citations.

A Novel Multi-bit Watermarking Algorithm Based on HVS

Abstract: This paper propose a novel adaptive multi-bit digital image watermarking algorithm based on discrete cosine transform and human visual system. This algorithm has several characteristics: first, embed 2 bits water-marking information into one embedding point is realized. Second, HVS property is used to embed watermark adaptively in the texture direction of visual insensitive area. Experimental results show that the proposed watermarking scheme is imperceptible and robust against various signal processing such as cropping, JPEG compression, filtering, noise adding and image enhancement, etc.

Watermarking Scheme Resilient to Geometrical Attacks Base Normalized Feature Area

Abstract: The crucial of design a robust image watermarking scheme is cope with geometrical attacks in transform domain.In this paper, a novel feature-based image watermarking scheme resilient to the geometrical attacks is proposed. Firstly, the harris-affine detector is utilized to extract invariant feature points from the host image. Then, by the feature scale of the local structure, the feature regions are adaptively computed and normalized. Finally, several copies of the digital watermark are embedded into the nonoverlapped local feature regions by quantizing the magnitude vectors of the DFT middle frequency. During detection, the resynchronization is achieved through feature points. And the embedded sequence can be extracted by “majority principles” without resorting to the original host image. Experimental results show that the proposed algorithm has good transparency and is very robust to common image processing and geometric attacks.

Screen-Shooting Resilient Watermarking

Abstract: This paper proposes a novel screen-shooting resilient watermarking scheme, which means that if the watermarked image is displayed on the screen and the screen information is captured by the camera, we can still extract the watermark message from the captured photo. To realize such demands, we analyzed the special distortions caused by the screen-shooting process, including lens distortion, light source distortion, and moire distortion. To resist the geometric deformation caused by lens distortion, we proposed an intensity-based scale-invariant feature transform (I-SIFT) algorithm which can accurately locate the embedding regions. As for the loss of image details caused by light source distortion and moire distortion, we put forward a small-size template algorithm to repeatedly embed the watermark into different regions, so that at least one complete information region can survive from distortions. At the extraction side, we designed a cross-validation-based extraction algorithm to cope with repeated embedding. The validity and correctness of the extraction method are verified by hypothesis testing. Furthermore, to boost the extraction speed, we proposed a SIFT feature editing algorithm to enhance the intensity of the keypoints, based on which, the extraction accuracy and extraction speed can be greatly improved. The experimental results show that the proposed watermarking scheme achieves high robustness for screen-shooting process. Compared with the previous schemes, our algorithm provides significant improvement in robustness for screen-shooting process and extraction efficiency.

Joint watermarking and lossless JPEG-LS compression for medical image security

Abstract: In this paper, we present a new joint watermarking-compression scheme the originality of which stands in the combination of the lossless compression standard JPEG-LS with the bit substitution watermarking modulation. This scheme allows the access to watermarking-based security services without decompressing the image. It becomes possible to trace images or to verify their authenticity directly from their compressed bitstream. Performance of our scheme, expressed in terms of embedding capacity and distortion, are evaluated on ultrasound images. They show that the watermarked images do not perceptually differ from their original counterparts while offering a capacity large enough to support various security services.

A robust image watermarking scheme in DCT domain based on adaptive texture direction quantization

Abstract: This paper proposes a novel robust image watermarking scheme in Discrete Cosine Transform (DCT) domain for active forensics. We investigate the relation between the positions and the modification magnitudes of DCT coefficients and directions of texture blocks. By exploring such relation, a direction-coefficient mapping is designed. First, the texture direction of each image block is estimated by Gabor filter. And then, according to the direction-coefficient mapping, one watermark bit is embedded into each block along its texture direction. Compared with existing schemes, the proposed method utilizes the direction features of texture blocks better . Therefore, the improvements in watermarked image quality and the robustness of watermark signal against image processing attacks are both achieved.

A simple image-adaptive watermarking algorithm with blind extraction

Abstract: In this paper, we propose an adaptive, DCT based, blind image watermarking algorithm. The adaptability is developed, while exploring the properties of the human visual system (HVS), to embed robust watermarks in DCT matrices while making them the least visible in the space domain. In the algorithm, binary watermarks are embedded in image blocks having gray level variations sufficient to mask a certain level of signal alterations. The orientations of the variations in such a block are detected by examining the locations of the most significant DCT coefficients in the matrix and a particular DCT coefficient is then chosen for watermark embedding with a view to making the gray level changes resulting from the embedding have a similar orientation with the original image signal to mask the watermark better. Moreover, the embedding strength is made to depend on the DC component, as it indicates the brightness of the image block, to further reduce the visibility of the watermark. The algorithm is computationally simple because it extracts the needed features directly from the DCT coefficients. Simulation results show that the algorithm is highly robust against JPEG compression even at low quality factors while maintaining high visual quality. Furthermore, the computational simplicity of the algorithm makes it very useful in real-time applications.