Nov 20, 2019 Transient signals are characteristic of the underlying phenomenon generating them, which makes their analysis useful in many fields. Transients occur as a sudden change between two steady state regimes, subsist for a short period, and tend to decay over time. Hence, superimposed damped sinusoids (SDS) were extensively used for transients modeling as they are adequate for describing.
![]()
You’ve seen hiring tests before. Maybe they’re a series of questions your boss came up with, maybe they’re a list of riddles that a qualified candidate should have no problem solving. Whatever the case, you know deep down they don’t work.
Knowing that doesn’t fix your problem though. As a hiring professional, you need an efficient way to screen candidates effectively, easily, and correctly.That’s where WonScore by Wonderlic comes in. Backed by extensive scientific I/O research, the WonScore assessment analyzes three crucial components of a candidate: cognitive ability, personality, and motivation. Using this data, we ensure that you as the employer are hiring the very most qualified person for your position and your team.
You’re able to access all of the results, which boil down to one score you can compare based on your needs. It’s quick, easy, painless, and most importantly it works.
The rapid developments of storage technology and information exchange encourage the development of research in the field of information security. In the process of sending information, tamper and issues about data ownership may occur. The fragile watermarking is one technique that can overcome the problem, in which this technique exploits sensitivity to tamper with the inserted watermark components.
Therefore, it is not tolerable to change even only one bit. Self-embedding can be defined as some important features obtained from a selected image as a watermark by modifying the pixel value of the original image.
Once a picture which has been inserted with a watermark is modified by other users, it can be used for tamper detection and recovery images. Due to the importance of this fragile watermarking scheme, this paper discusses the principles and characteristics of a fragile watermarking algorithm. The main contribution of this paper survey is that it summarises the current mechanisms of selection, generation, method of watermark insertion, detection and tamper localisation and recovery procedures. Comparison of several watermarking techniques was analysed and presented in tabular form, as well as experimental evaluation of four watermarking schemes in many graphs to show the performance of the self-embedding fragile watermarking scheme. Currently, the availability of image processing technology is highly diverse, thus an image content becomes easily manipulated by irresponsible parties. Replacement of content is very harmful to the owner especially when it comes to legal cases.
Therefore, research on detection and localisation of tampered images is an important issue. One approach that is widely used is the technique of digital watermarking. This is a technique of inserting secret information or image’s information into an original image prior to sending.
The original image is the image where the confidential information is inserted, while the secret information is a watermark ,. The watermark component selection is done by considering the purpose of the watermarking technique. In general, the watermark used for image authentication and recovery uses two watermarks, which are bit authentication and bit recovery. For image recovery, bit recovery is selected from the image feature, usually from the original image compression form.
![]()
When the watermark used is generated from the original image, it is known as the self-embedding watermarking scheme ,.In general, digital watermarking techniques can be categorised as robust watermarking, fragile watermarking and semi-fragile watermarking. Watermark is specifically selected to be able to withstand deliberate or intentional manipulation, in this case belonging to a strong watermarking category, commonly used for copyright and verification of the image ,. In the fragile watermarking technique that is being used for the authentication process, the embedded watermark vulnerability indicates that there are modifications either intentionally or unintentionally ,. Meanwhile, in semi-fragile watermarking techniques, there are common image processing methods, such as JPEG compression, scaling, sharpening; and tidy against deliberate manipulations, such as content modified by false information, then the watermark is designed to be able to resist a variety of non-heretical attacks ,.For the purposes of authentication, fragile watermarking schemes can be categorised into two main categories as fragile watermarking pixel-wise schemes and fragile watermarking block-wise schemes ,. In the pixel-wise fragile watermarking scheme, the watermark information is generated from the grey pixel value of the host and inserted into the host pixel. Meanwhile, in the fragile watermarking scheme of block-wise, the original image is subdivided into blocks.
Each sub-block has watermark information and is authenticated with a watermark retrieval successfully embedded in it. If the watermarked image is modified, the watermark of a sub-block is not successfully retrieved, and then the sub-block is identified as a damaged or incorrect block. The fragile nature for authentication applications is also used in reversible data hiding techniques. According to , most reversible watermarking techniques are fragile and allow for extracting watermarks along with the complete restoration of the original image. Reversible data hiding methods for uncompressed images have been discussed in , where there are two criteria to show their performances, i.e. Imperceptibility and planting capacity.
Imperceptibility is a measure of similarity between watermarked and covers images. Meanwhile, the capacity of embedding is a measure of the maximum number of bits of information that can be pinned on the cover image. The least significant bit (LSB) method in data hiding has simplicity, easy detection and high embedding capabilities ,. The LSB method, therefore, is generally preferred for embedding watermarks on fragile image watermarking.To facilitate the understanding of fragile watermarking, in addition to the discussion of conceptual understanding, this article also explains the comparison of methods ranging from insertion, extraction and recovery results. At the end, the analysis of the results of the evaluation is also described by selecting four methods that represent spatial domains to experiment with many tampered images. A block diagram in Fig. Provides a brief overview of the self-embedding fragile watermarking scheme for image authentication.
Basic principles of self-embedding fragile watermarking schemeIn recent years, more research in the field of fragile watermarking is aimed at the process of damaged image authentication and recovery. This method can be derived under distinct purposes.
According to the mechanism of image capture feature, it can be divided into block-wise and pixel-wise mechanisms as shown in Fig. From Cheng et al. ; the block-wise algorithm , divides the original image into small blocks to embed a watermark, which may be a hash of the main content taken from each block. The block-wise algorithm can locate the damaged block, but the blocks may contain some original pixels, so that the accuracy of the localisation placement is decreasing. This is the weakness of the block-wise algorithm. The pixel-based algorithm , generates data from the original pixel grey value and embeds the mark into the pixel.
By calculating the consistency of the extracted watermark and its derivative signal, we can detect the damaged pixels. However, due to the limited precision of biplanes, it is possible that the data derived from the damaged pixels equal the watermark even though it has been modified. Therefore, modifications to these pixels are not directly detected.There are two stages of the watermarking algorithm for image tamper detection and recovery; the embedding watermark phase and authentication phase which are then followed by tamper detection and recovery image , as shown in the Figs. Based on some characteristics, there are several categories used to estimate the effectiveness of a self-recovery fragile watermarking technique , :.Perceptibility: the embedded watermark must be invisible. It will be hard to identify it with human vision; only authorised user will be able to recover it.
Xiao’s method divides an image into 4 × 4 non-overlapping blocks, generates authentication watermarks for the blocks by comparison and parity check among average intensities and embeds them into corresponding blocks. The recovery information of another block is embedded into its mapping block. Huo et al.’s scheme proposes the recovery of discrete cosine transform (DCT-based) alternate self-recovery fragile watermarking scheme. The image was divided into non-overlapping sub-blocks with 8 × 8 sizes and sub-blocks classified into different types according to block variance.
Experiments in als.
![]() Comments are closed.
|
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
January 2023
Categories |