Activity profiling for minimally invasive surgery

Imperial Users onl

Recognising facial expressions in video sequences

We introduce a system that processes a sequence of images of a front-facing human face and recognises a set of facial expressions. We use an efficient appearance-based face tracker to locate the face in the image sequence and estimate the deformation of its non-rigid components. The tracker works in real-time. It is robust to strong illumination changes and factors out changes in appearance caused by illumination from changes due to face deformation. We adopt a model-based approach for facial expression recognition. In our model, an image of a face is represented by a point in a deformation space. The variability of the classes of images associated to facial expressions are represented by a set of samples which model a low-dimensional manifold in the space of deformations. We introduce a probabilistic procedure based on a nearest-neighbour approach to combine the information provided by the incoming image sequence with the prior information stored in the expression manifold in order to compute a posterior probability associated to a facial expression. In the experiments conducted we show that this system is able to work in an unconstrained environment with strong changes in illumination and face location. It achieves an 89\% recognition rate in a set of 333 sequences from the Cohn-Kanade data base

Machine Analysis of Facial Expressions

No abstract

Symmetric- Based Steganography Technique Using Spiral-Searching Method for HSV Color Images

إخفاء المعلومات يعني أخفاء المعلومات السرية في بعض الوسائط المختارة الأخرى دون ترك أي دليل واضح على تغيير ميزات الوسط الناقل. تخفي معظم طرق الاختباء التقليدية الرسالة مباشرةً في الوسائط الناقلة مثل (النص والصورة والصوت والفيديو). يترك بعض الاخفاء تأثيرًا سلبيًا على صورة الغلاف الناقلة، هذا التأثير السلبي يًمكن من اكتشاف التغير في والوسط الناقل من خلال الإنسان والآلة. الغرض من طريقة إخفاء المعلومات المقترحة هو ان جعل هذا التغيير غير قابل للكشف، يركز البحث الحالي على استخدام طريقة معقدة لمنع الكشف عن إخفاء المعلومات بواسطة الإنسان والآلة باعتماد على طريقة البحث اللولبي، تم استخدام مقاييس مؤشر التشابه الهيكلي للقياس للحصول على دقة وجودة الصورة المستردة وتم تحسين جودتها المدركة. تم حساب قيم مقاييس المعلومات من خلال التجارب العملية (الإدراك، المتانة، السعة) باستخدام تقنية الاستيفاء ومقاييس التشابه الهيكلي. تظهر النتائج التجريبية أن استخدام هذه المقاييس (PSNR و MSE و SSIM) قد حسن جودة الصورة بنسبة 87٪ وأنتج قيم PSNR (38-41 ديسيبل) و MSE = 0.6537 و SSIM = 0.8255. توضح النتائج أيضًا تقدمًا ملحوظًا في مجال إخفاء المعلومات وتزايد صعوبة اكتشافها من قِبل البشر والآلات.Steganography is defined as hiding confidential information in some other chosen media without leaving any clear evidence of changing the media's features. Most traditional hiding methods hide the message directly in the covered media like (text, image, audio, and video). Some hiding techniques leave a negative effect on the cover image, so sometimes the change in the carrier medium can be detected by human and machine. The purpose of suggesting hiding information is to make this change undetectable. The current research focuses on using complex method to prevent the detection of hiding information by human and machine based on spiral search method, the Structural Similarity Index Metrics measures are used to get the accuracy and quality of the retrieved image and to improve its perceived quality. The values of information measures are calculated through practical experiments of (perceptibility, robustness, capacity) by using interpolation technique and structural similarity measures. Experimental results show that the use of these measures (PSNR, MSE, and SSIM) has improved the image quality by 87% and has produced values of PSNR (38-41 dB), MSE = 0.6537 and SSIM= 0.8255. The results also demonstrate a remarkable progress in the field of hiding information and the increasing difficulty of detecting it by humans and machines

Data Hiding in Digital Video

With the rapid development of digital multimedia technologies, an old method which is called steganography has been sought to be a solution for data hiding applications such as digital watermarking and covert communication. Steganography is the art of secret communication using a cover signal, e.g., video, audio, image etc., whereas the counter-technique, detecting the existence of such as a channel through a statistically trained classifier, is called steganalysis. The state-of-the art data hiding algorithms utilize features; such as Discrete Cosine Transform (DCT) coefficients, pixel values, motion vectors etc., of the cover signal to convey the message to the receiver side. The goal of embedding algorithm is to maximize the number of bits sent to the decoder side (embedding capacity) with maximum robustness against attacks while keeping the perceptual and statistical distortions (security) low. Data Hiding schemes are characterized by these three conflicting requirements: security against steganalysis, robustness against channel associated and/or intentional distortions, and the capacity in terms of the embedded payload. Depending upon the application it is the designer\u27s task to find an optimum solution amongst them. The goal of this thesis is to develop a novel data hiding scheme to establish a covert channel satisfying statistical and perceptual invisibility with moderate rate capacity and robustness to combat steganalysis based detection. The idea behind the proposed method is the alteration of Video Object (VO) trajectory coordinates to convey the message to the receiver side by perturbing the centroid coordinates of the VO. Firstly, the VO is selected by the user and tracked through the frames by using a simple region based search strategy and morphological operations. After the trajectory coordinates are obtained, the perturbation of the coordinates implemented through the usage of a non-linear embedding function, such as a polar quantizer where both the magnitude and phase of the motion is used. However, the perturbations made to the motion magnitude and phase were kept small to preserve the semantic meaning of the object motion trajectory. The proposed method is well suited to the video sequences in which VOs have smooth motion trajectories. Examples of these types could be found in sports videos in which the ball is the focus of attention and exhibits various motion types, e.g., rolling on the ground, flying in the air, being possessed by a player, etc. Different sports video sequences have been tested by using the proposed method. Through the experimental results, it is shown that the proposed method achieved the goal of both statistical and perceptual invisibility with moderate rate embedding capacity under AWGN channel with varying noise variances. This achievement is important as the first step for both active and passive steganalysis is the detection of the existence of covert channel. This work has multiple contributions in the field of data hiding. Firstly, it is the first example of a data hiding method in which the trajectory of a VO is used. Secondly, this work has contributed towards improving steganographic security by providing new features: the coordinate location and semantic meaning of the object

Digital watermarking by utilizing the properties of self-organization map based on least significant bit and most significant bit

Information security is one of the most important branches concerned with maintaining the confidentiality and reliability of data and the medium for which it is transmitted. Digital watermarking is one of the common techniques in this field and it is developing greatly and rapidly due to the great importance it represents in the field of reliability and security. Most modern watermarking systems, however, use the self-organization map (SOM), which is safer than other algorithms because an unauthorized user cannot see the result of the SOM's training. Our method presents a semi-fragile watermark under spatial domain using least significant bit (LSB) and by relying on most significant bit (MSB) when the taken values equal to (2 or 4 bits) depending on the characteristics of SOM through developing the so-called best matching unit (BMU) which working to determine the best location for concealment. As a result, it shows us the ability of the proposed method to maintain the quality of the host with the ability to retrieve data, whether it is a binary image or a secret message

Exploring Noise as Information

My art practice is based on the study of machines. Instead of focusing on how machines usually work, I discover and explore the noise of machines – both visually and aurally. In my work, I use a photocopier to scan and print the same image repeatedly, which results in the original image becoming distorted and abstracted with noise. This work was initially influenced by the distorted homework paper handouts I regularly received at the school in China as a child – many of which were nearly illegible. In my practice, I explore the idea of noise as information. To help provide background to this work, I discuss three main aspects: glitch art, the actor-network theory, and how it connects to my work. Through my studio projects I have explored how noise, which is often viewed as an unwanted by product, can be used as the main content of a piece of work. Each form of communication technology has its own types of noise, which has its own aesthetic and style – and my hope is that my projects highlight the beauty and texture of noise that is usually only considered in a negative way