A novel block-level perceptual image watermarking framework is proposed in this study, including tridirectional correlation and a block-level just noticeable difference (JND) model. Specifically, the difference in the discrete cosine transform (DCT) coefficients of two blocks is calculated based on three directions in the neighborhood, called the tri-directional correlation (TriDC). Additionally, the representative alternating current (AC) coefficients along horizontal, vertical, and diagonal directions, which can describe structural patterns, are projected and merged for TriDC differences. Then, the difference of the DCT coefficient is modulated to a predefined zone depending on the JNDbased offset. Finally, the extent of the watermarked AC coefficients is determined with perceptual JND adjustment. The experimental results demonstrate that the proposed scheme can protect most common image processing attacks; and has better robustness compared with recent zone modulation watermarking schemes and traditional watermarking methods.image watermarking, JND model, robustness, spread transform, tri-directional With the rapid development of digital technologies within the past few decades, digital images are more convenient for transmission, duplication, and modification, which means the ease of several urgent issues relating to copyright protection and authentication. It is increasingly important to be able to improve image security and protection against illegal actions and possible violations during distribution over communications links; and computer networks. [1][2][3][4][5][6] Digital watermarking is a robust and maintainable solution for data hiding, whereby the watermark is embedded into the host image, and extracted to identify ownership.In this paper, we focus on image watermarking. Image watermarking can be effective only if the watermarked image has minimum distortion, and the watermark can be extracted with maximum robustness. Unfortunately, there exists a contradiction between the image fidelity and robustness for the image watermarking method. Generally, increasing the robustness occurs at the cost of hampering the quality and utility of the image, and vice versa. They are mutually constrained. Consequently, a better tradeoff between fidelity and robustness is required for a well-designed watermarking algorithm.Currently, the common embedding schemes fall into two categories, namely spatial and transformed domain schemes. Both of them have their inherent characteristics. The former has lower computational complexity but poor robustness. The latter can significantly improve robustness while ensuring image quality. They also have an acquired deficiency, using equal embedding strength for different regions in the image, which intensifies the contradiction between the robustness and fidelity. The discrete cosine transform (DCT), most popular in the transform domain, has been applied for software and hardware implementations in low-cost devices.This paper addresses these issues by studying the correlation betwe...