Removable visible image watermarking algorithm in the discrete cosine transform domain

Abstract

A removable visible watermarking scheme, which operates in the discrete cosine transform (DCT) domain, is proposed for combating copyright piracy. First, the original watermark image is divided into 16ϫ 16 blocks and the preprocessed watermark to be embedded is generated by performing element-by-element matrix multiplication on the DCT coefficient matrix of each block and a key-based matrix. The intention of generating the preprocessed watermark is to guarantee the infeasibility of the illegal removal of the embedded watermark by the unauthorized users. Then, adaptive scaling and embedding factors are computed for each block of the host image and the preprocessed watermark according to the features of the corresponding blocks to better match the human visual system characteristics. Finally, the significant DCT coefficients of the preprocessed watermark are adaptively added to those of the host image to yield the watermarked image. The watermarking system is robust against compression to some extent. The performance of the proposed method is verified, and the test results show that the introduced scheme succeeds in preventing the embedded watermark from illegal removal. Moreover, experimental results demonstrate that legally recovered images can achieve superior visual effects, and peak signal-to-noise ratio values of these images are Ͼ50 dB.

A novel embedding technique for lossless data hiding in medical images employing histogram shifting method

“…11 In this scheme, wavelets have been successfully used in image enhancement analysis and histogram shifting. 33 These wavelets are represented with good resolution, in different frequency subbands. The characteristic feature of histogram shifting is that it provides a compact representation of the image.…”

A Contrast-Sensitive Reversible Visible Image Watermarking Technique

“…In most conventional visible watermarking schemes [1]- [5], a visible watermark is usually designed to be irremovable in order to effectively resist unintended editing and malicious attacks [6]- [8]. However, in some potential applications, a visible watermark is required to be removable [9]- [13]. Depending upon whether the original signal is perfectly recovered or not after watermark removal, removable visible watermarking can be further classified into the following two categories: irreversible and reversible.…”

Removable Visible Watermarking Using Discrete Fourier Transform

“…The key used is a random variable with discrete normal distribution. Yang et al (2008) [19] proposed a removable visible watermarking using DCT. The visible watermark was removable using secret key.…”