Color medical image lossless watermarking using chaotic system and accurate quaternion polar harmonic transforms.

Highlights • QPHTs are applied to color medical image lossless watermarking algorithm for the first time. • Chaotic system is used to enhance the security of the proposed scheme. • The scheme does not make any changes to the original medical image to ensure the integrity of the medical image. • The accurate coefficients selection of QPHTs and the comparison of stability with different choices of μ are discussed in detail. Abstract With the increasingly widespread use of medical images in medical institutions and networks, the copyright protection of medical images has become increasingly urgent. Since traditional embedded watermarking technology degrades the quality of the original images, it is not suitable for medical images. In addition, most medical watermarking algorithms are aimed at grayscale images; therefore, a smaller number of color medical image watermarking algorithms are available. In this paper, we propose a lossless watermarking scheme for color medical image copyright protection based on a chaotic system and quaternion polar harmonic transforms (QPHTs), which is a quaternion orthogonal moment method. In watermark embedding, we compute the QPHTs for the original color medical image and select accurate coefficients to construct a zero-watermark image. Then, the zero-watermark image is stored in the intellectual property right (IPR) database. Experimental results show that the proposed scheme is robust to geometric attacks and common attacks and that it has better performance than similar lossless watermarking schemes. In addition, this paper details the selection of accurate coefficients for QPHTs and compares stability with different choices of unit pure quaternions. [ABSTRACT FROM AUTHOR]