A Combined DWT and DCT Watermarking Scheme Optimized Using Genetic Algorithm

Abstract

To protect the copyright of digital image, this paper proposed a combined Discrete Wavelet Transform (DWT) and Discrete Cosine Transform (DCT) based watermarking scheme. To embed the watermark, the cover image was decomposed by a 2-level DWT, and the HL2 sub-band coefficient was divided into 4x4 blocks, then the DCT was performed on each of these blocks. The watermark bit was embedded by predefined pattern_0 or pattern_1 on the middle band coefficients of DCT. After watermark insertion, inverse DCT was applied to each of the 4x4 blocks of HL2 sub-band coefficient, and inverse DWT was applied to obtain the watermarked image. For watermark extraction, the watermarked image, which may be attacked by various image attacks, was decomposed with 2-level DWT and DCT similarly as watermark embedding process, then correlation between middle band coefficients of block DCT and the predefined pattern (pattern_0 and pattern_1) was calculated to decide whether a bit 0 or a bit 1 was embedded. Genetic algorithm was used for embedding and extraction parameters optimization. Optimization is to maximize PSNR of the watermarked image and NCC of the extracted watermark. Experiment results show that the proposed scheme in this paper is robust against many image attacks, and improvement can be observed when compared to other existing schemes

A blind robust image watermarking approach exploiting the DFT magnitude

“…In order to evaluate the robustness against JPEG compression, we compressed the watermarked images "Mandrill", "Peppers", "cameraman", "Lena" and "Goldhill" by different quality factors and we summarize the average NC values for the five test images. Afterwards, we compare our scheme to [11] and [12]. Table IV shows the NC values, which are almost close to 1, obtained after JPEG attack with their corresponding PSNR values in the case of "Mandrill".…”

“…Table IV shows the NC values, which are almost close to 1, obtained after JPEG attack with their corresponding PSNR values in the case of "Mandrill". It can be seen from Table VII and Table VIII that our method gives better results than approaches in [11] and [12]. According to Table III, it can be observed that our method is robust against noising attack and gives better results.…”

“…4. We choose to compare our scheme with schemes presented in [11] and [12], in terms of imperceptibility and robustness. For this purpose, another (64 × 64) binary image is used as watermark.…”

Watermark Embedding and Extraction Scheme Design by Two-stage Optimization for Illegal Replication Detection of Two-dimensional Barcodes

“…The objective function is the linear sum of three objectives: visual quality, robustness, and amount of embedded information. Mingzhi and Yan (Mingzhi et al, 2013) proposed a combined DWT and Discrete Cosine Transform (DCT) scheme (Rao and Yip, 1990), based on a watermarking scheme optimized by genetic algorithm (GA) (Goldberg, 1989). In this method, fitness calculations are performed on images corrupted by attacks, such as JPEG compression, Gaussian filtering, image sharpening, and cropping.…”

Multi-objective Particle Swarm Optimization Based Image Watermarking Scheme

“…These algorithms are fragile to manipulations, but they have little computation work and can be easily implemented. The transform domain watermarking schemes are mainly concentrated on some signal transforms such as DCT(Discrete Cosine Transform) [5,6], DFT(Discrete Fourier Transform) [7] and DWT(Discrete Wavelet Transform) [8][9][10], etc. The watermark is embedded into the host by modifying some or all frequency domain coefficients, especially middle frequency coefficients.…”