1,486 research outputs found
Robust Object-Based Watermarking Using SURF Feature Matching and DFT Domain
In this paper we propose a robust object-based watermarking method, in which the watermark is embedded into the middle frequencies band of the Discrete Fourier Transform (DFT) magnitude of the selected object region, altogether with the Speeded Up Robust Feature (SURF) algorithm to allow the correct watermark detection, even if the watermarked image has been distorted. To recognize the selected object region after geometric distortions, during the embedding process the SURF features are estimated and stored in advance to be used during the detection process. In the detection stage, the SURF features of the distorted image are estimated and match them with the stored ones. From the matching result, SURF features are used to compute the Affine-transformation parameters and the object region is recovered. The quality of the watermarked image is measured using the Peak Signal to Noise Ratio (PSNR), Structural Similarity Index (SSIM) and the Visual Information Fidelity (VIF). The experimental results show the proposed method provides robustness against several geometric distortions, signal processing operations and combined distortions. The receiver operating characteristics (ROC) curves also show the desirable detection performance of the proposed method. The comparison with a previously reported methods based on different techniques is also provided
Copyright Protection of Color Imaging Using Robust-Encoded Watermarking
In this paper we present a robust-encoded watermarking method applied to color images for copyright protection, which presents robustness against several geometric and signal processing distortions. Trade-off between payload, robustness and imperceptibility is a very important aspect which has to be considered when a watermark algorithm is designed. In our proposed scheme, previously to be embedded into the image, the watermark signal is encoded using a convolutional encoder, which can perform forward error correction achieving better robustness performance. Then, the embedding process is carried out through the discrete cosine transform domain (DCT) of an image using the image normalization technique to accomplish robustness against geometric and signal processing distortions. The embedded watermark coded bits are extracted and decoded using the Viterbi algorithm. In order to determine the presence or absence of the watermark into the image we compute the bit error rate (BER) between the recovered and the original watermark data sequence. The quality of the watermarked image is measured using the well-known indices: Peak Signal to Noise Ratio (PSNR), Visual Information Fidelity (VIF) and Structural Similarity Index (SSIM). The color difference between the watermarked and original images is obtained by using the Normalized Color Difference (NCD) measure. The experimental results show that the proposed method provides good performance in terms of imperceptibility and robustness. The comparison among the proposed and previously reported methods based on different techniques is also provided
Application of a CC-VSI for Active Filtering and Photovoltaic Energy Conversion with a 1-to-1 MPPT Controller
This paper focuses on the implementation of a three-phase four wire current-controlled Voltage Source Inverter (CC-VSI) as both PV energy extraction and power quality improvement. For power quality improvement, the CC-VSI works as a grid current-controller shunt active power filter. Then, the PV array supported by a Look-up Table type of a MPPT controller is coupled to the DC bus of the CC-VSI. The output of MPPT controller is a DC voltage that determines the DC-bus voltage according to the PV maximum power. The computer simulation results show that the system works properly in steady state and dynamic condition
Long-term follow-up of atrial contraction following the maze procedure in patients with mitral valvular disease
A Mini-Orange Spectrometer for Internal Conversion Measurement in ISOL and In-Beam Experiments
開始ページ、終了ページ: 冊子体のページ付
Acoustic Journal Bearing with Changeable Geometry and Built-in Flexibility
The influence of embodiment flexibility on the performance of an acoustic journal bearing is
presented. Two completely different embodiments of the bearing were investigated using
three criteria of performance assessment that is torque at the start-up, amount of separation
due to squeeze film pressure and motion stability of the shaft running at speed. The
embodiment with built-in flexibility proved to perform far better that the bearing which
overall flexibility was much less. However, considerations pertinent to the easy of machining
and fatigue endurance mitigate the ranking of performance of the two embodiments
investigated.National Centre of Scienc
- …