This paper proposes a new blind watermarking algorithm, which embedding the binary watermark into the blue component of a RGB image in the spatial domain, to resolve the problem of protecting copyright. For embedding watermark, the generation principle and distribution features of direct current (DC) coefficient are used to directly modify the pixel values in the spatial domain, and then four different sub-watermarks are embedded into the different areas of the host image for four times, respectively. When watermark extraction, the sub-watermark is extracted with blind manner according to DC coefficients of watermarked image and the key-based quantization step, and then the statistical rule and the method of “first to select, second to combine” are proposed to form the final watermark. Hence, the proposed algorithm is executed in the spatial domain rather than in discrete cosine transform (DCT) domain, which not only has simple and quick performance of the spatial domain but also has high robustness feature of DCT domain. The experimental results show that the proposed watermarking algorithm can obtain better invisibility of watermark and stronger robustness for common attacks, e.g., JPEG compression, cropping, and adding noise. Comparison results also show the advantages of the proposed method.

Robust color image watermarking technique in the spatial domain

In this paper, a blind image watermarking scheme based on discrete wavelet transform (DWT) and singular value decomposition (SVD) is proposed. In this scheme, DWT is applied on ROI (region of interest) of the medical image to get different frequency subbands of its wavelet decomposition. On the low frequency subband LL of the ROI, block-SVD is applied to get different singular matrices. A pair of elements with similar values is identified from the left singular value matrix of these selected blocks. The values of these pairs are modified using certain threshold to embed a bit of watermark content. Appropriate threshold is chosen to achieve the imperceptibility and robustness of medical image and watermark contents respectively. For authentication and identification of original medical image, one watermark image (logo) and other text watermark have been used. The watermark image provides authentication whereas the text data represents electronic patient record (EPR) for identification. At receiving end, blind recovery of both watermark contents is performed by a similar comparison scheme used during the embedding process. The proposed algorithm is applied on various groups of medical images like X-ray, CT scan and mammography. This scheme offers better visibility of watermarked image and recovery of watermark content due to DWT-SVD combination. Moreover, use of Hamming error correcting code (ECC) on EPR text bits reduces the BER and thus provides better recovery of EPR. The performance of proposed algorithm with EPR data coding by Hamming code is compared with the BCH error correcting code and it is found that later one perform better. A result analysis shows that imperceptibility of watermarked image is better as PSNR is above 43 dB and WPSNR is above 52 dB for all set of images. In addition, robustness of the scheme is better than existing scheme for similar set of medical images in terms of normalized correlation coefficient (NCC) and bit-error-rate (BER). An analysis is also carried out to verify the performance of the proposed scheme for different size of watermark contents (image and EPR data). It is observed from analysis that the proposed scheme is also appropriate for watermarking of color image. Using proposed scheme, watermark contents are extracted successfully under various noise attacks like JPEG compression, filtering, Gaussian noise, Salt and pepper noise, cropping, filtering and rotation. Performance comparison of proposed scheme with existing schemes shows proposed scheme has better robustness against different types of attacks. Moreover, the proposed scheme is also robust under set of benchmark attacks known as checkmark attacks.

A blind medical image watermarking: DWT-SVD based robust and secure approach for telemedicine applications

The ever-growing numbers of medical digital images and the need to share them among specialists and hospitals for better and more accurate diagnosis require that patients’ privacy be protected. As a result of this, there is a need for medical image watermarking (MIW). However, MIW needs to be performed with special care for two reasons. Firstly, the watermarking procedure cannot compromise the quality of the image. Secondly, confidential patient information embedded within the image should be flawlessly retrievable without risk of error after image decompressing. Despite extensive research undertaken in this area, there is still no method available to fulfill all the requirements of MIW. This paper aims to provide a useful survey on watermarking and offer a clear perspective for interested researchers by analyzing the strengths and weaknesses of different existing methods.

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Watermarking Techniques used in Medical Images: a Survey

In this paper, a novel robust color image watermarking method based on Discrete Cosine Transform (DCT) and Discrete Wavelet Transform (DWT) is proposed. In this method, RGB cover image is divided into red, green and blue components. DCT and DWT are applied to each color components. Grayscale watermark image is scrambled by using Arnold transform. DCT is performed to the scrambled watermark image. Transformed watermark image is then divided into equal smaller parts. DCT coefficients of each watermark parts are embedded into four DWT bands of the color components of the cover image. The robustness of the proposed color image watermarking has been demonstrated by applying various image processing operations such as rotating, resizing, filtering, jpeg compression, and noise adding to the watermarked images. Experimental results show that the proposed method is robust to the linear and nonlinear attacks and the transparency of the watermarked images has been protected.

A novel hybrid DCT and DWT based robust watermarking algorithm for color images

This paper presents lifting wavelet transform (LWT) and discrete cosine transform (DCT) based robust watermarking approach for tele-health applications. For identity authentication, ‘signature watermark’ of size ‘64 × 64’ and ‘patient report’ of size ‘80’ characters are hiding into the host medical image. Further, the signature watermark is encrypted by message-digest (MD5) and ‘patient report’ is encoded by BCH error correcting code before embedding into the host image. Experimental demonstrations indicate that the method provides sufficient robustness and security against various attacks without significant distortion between cover and watermarked image. Further, our results proved that the method offer NC value more than 0.9214 for most of the considered attacks. Furthermore, it is evident from results our method shows the improvement in robustness to previously reported techniques under consideration while providing low computational complexity.

Robust and distortion control dual watermarking in LWT domain using DCT and error correction code for color medical image

We have presented an algorithm of digital image watermarking for color images which we implemented in frequency domain. Before inserting the watermark, we added the Hamming codes row wise as well column wise in the intensity component of color image. Two encryption techniques were implemented on the ECC inserted watermark for its security. The pixel position for inserting the watermark was calculated using starting row and column number for that 8?×?8 block. Pixel embedding strength is calculated using criteria that low frequency is robust in general signal processing attacks, thus choosing less value to be embedded and vice-versa. Results show that the watermarking algorithm is robust against common signal processing attacks. The algorithm is tested against multiple attacks also.

Adaptive digital image watermarking for color images in frequency domain

Piracy in the presence of internet and computers proves to be a biggest jolt to the concerned industry. To reduce the piracy and duplicity of the images, digital watermarking technique is having an edge over the other available techniques. In this paper, a blind digital watermarking algorithm is presented which is robust enough to resist the watermark against the attacks. The algorithm exploits the random sequence generated by Arnold and Chaos transformations. Discrete wavelet transformation of third level decomposition is used to convert the image into its frequency domain. The binary watermark is embedded into its HL3 domain. The evaluation of the algorithm is calculated in terms of peak signal to noise ratio and non correlation. The results prove that the algorithm is robust enough to handle the attacks like JPEG, filtering, and different types of noise attacks.

Robust Blind Digital Image Watermarking Using DWT and Dual Encryption Technique

We propose an algorithm for image de-noising which uses a trimmed global mean filter with rank order absolute differences to remove random-valued impulse noise, stripes, scratches and blotches It is a two stage algorithm, in the first stage the corrupted candidate is detected using rank ordered absolute differences (ROAD) In the second stage, the corrupted pixels are replaced by the median of the uncorrupted pixels in the selected window Trimmed global mean filter is used if the selected window contains all the pixels as noisy candidate We used a fixed window size in both detection and filtering stages The visual and quantitative results show that proposed filter outperforms the existing filters in restoring image which is corrupted by random valued impulse noise The proposed algorithm also provides good results over the impulse noise image corrupted by artificially introduced scratches, blotches, and stripes without causing blurring

Efficient digital image denoising for gray scale images

Piracy in the presence of internet and computers proves to be a biggest jolt to the concerned industry. To reduce the piracy and duplicity of the images, digital watermarking technique is having an edge over the other available techniques. In this paper, a blind digital watermarking algorithm is presented which is robust enough to resist the watermark against the attacks. The algorithm exploits the random sequence generated by Arnold and Chaos transformations. Discrete wavelet transformation of third level decomposition is used to convert the image into its frequency domain. In another transformation, the image is converted into frequency domain by using DCT and DWT combined. The binary watermark is embedded into its HL3 domain. The evaluation of the algorithm is calculated in terms of peak signal to noise ratio and non correlation. The results prove that the algorithm is robust enough to handle the attacks like JPEG, filtering, and different types of noise attacks.

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Comparative Analysis of Blind Digital Image Watermarking Utilising Dual Encryption Technique in Frequency Domains

This study presented an algorithm to protect the copyright watermark by providing Hamming codes as error correcting technique. Watermark was embedded in frequency domain using discrete cosine transformation and discrete wavelet transformation, to enhance the susceptibility. Combinations of two techniques are used to target medium frequencies only. Randomness of the watermark is also created before embedding. Instead of embedding in the same place in every block, it is embedded adaptively which depends upon the row and column of that particular block. Results prove the effectiveness of the algorithm against various attacks like jpeg attack, filtering and addition of noises like Gaussian noise, salt and pepper noise and speckle noise. ECC proved to be effective to recover the watermark after certain attacks performed.

G.S. Kalra

Papers

Adaptive digital image watermarking for color images in frequency domain

Robust Blind Digital Image Watermarking Using DWT and Dual Encryption Technique

Efficient digital image denoising for gray scale images

Comparative Analysis of Blind Digital Image Watermarking Utilising Dual Encryption Technique in Frequency Domains

Digital Image Watermarking in Frequency Domain Using ECC and Dual Encryption Technique