Digital watermarking has been an effective technique for copy protection, copyright protection, medical application, data authentication, fingerprinting and other applications over recent years. In this technique, certain information called watermark is embedded inside the original data. The main data can be an image, video, audio and text. Requirements of a watermarking system will be different depending on the type of the host media and for what purpose it is used. In this article, a study on digital image watermarking is presented. In the study, general concepts of watermarking, different types of digital image watermarking, and the watermark embedding and extraction techniques are discussed in brief. پرونده مقاله

Compressed sensing (CS) is a new and promising framework for simultaneous sampling and compression of signals at sub-Nyquist rates. Under certain conditions, the signal can be reconstructed exactly from a small set of measurements via solving an optimization problem. In order to make this possible, compressed sensing is based on two principles of sparsity and incoherence. Compressed sensing takes advantage of the fact that most signals in nature are sparse or compressible, which means that when expressed in a suitable basis called as sparsifying basis, they will have a sparse representation. In the CS, the sparse signal is sampled by a non-adaptive linear sampling matrix. Then, based on the limited measurements obtained from the sampling matrix and using a non-linear algorithm, the original signal is reconstructed. The sparse signal reconstruction problem in the CS is an optimization problem that various algorithms have been proposed to solve it. The compressed sensing has a great application potential and can be used in a wide range of applications. Recently, deep learning has been used to solve the CS problem and its medical applications. In this paper, the generalities of compressed sensing are presented and CS reconstruction algorithms are reviewed. Also, the application of CS in magnetic resonance imaging (MRI) are investigated. پرونده مقاله