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A self-embedding watermarking algorithm based on a reference sharing mechanism that has recovery ability under high tampering rates is proposed in this paper. In existing methods, the image recovery ability is often limited under an increasing tampering rate. The proposed method overcomes this limitation by seeking an approximate solution for each character-bit group tampered with. Moreover, the priority assignment of such groups can enhance the accuracy of tampering recovery. Based on this, by using the method proposed in this paper, recovered images always maintain excellent visual quality even at relatively high tampering rates. The experimental results demonstrate the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

Image hashing is a technique that represents an image as a short unidirectional sequence. In this study, we propose a robust color image hashing technique based on the quaternionic local ranking binary pattern (QLRBP). First, the values of the RGB color channels are expressed as a pure quaternion, and the texture image is generated using the phase difference of the Clifford translation quaternion as the source for local binary pattern (LBP) comparison data. Next, mean pooling is used to reduce the dimensionality of the image texture. For security, the pixels of the dimension-reduced image are randomly selected, and each pixel is quantized to obtain the final image hash. Experimental results showed that the proposed scheme resists a variety of ordinary image operations and achieves good balance between robustness and discrimination. In comparison with other state-of-the-art methods, the receiver operating characteristic (ROC) curves of our scheme demonstrate its superiority in terms of content identification. [ABSTRACT FROM AUTHOR]