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International audience; In this paper a new method is presented for 3D terrain visualization via reversible JPEG2000-based blind data hiding with special focus on data synchronization and scalability. Online real-time 3D terrain visualization involves considerable amount of data. The process is essentially the mapping of the aerial photograph, called texture, onto its corresponding digital elevation model (DEM) implying at least two distinct data inputs. The presence of large disparate data necessitates a compression strategy on one hand and the integration of the DEM and texture into one unit on the other. Whilst the compression must accommodate the scalability requirement originated by the diversity of clients, the unification of data ought to be synchronous. For scalability this paper relies on the multi-resolution nature of the DWT-based JPEG2000 standard whereas the synchronized unification of DEM with the texture is realized by the application of a perceptually transparent data hiding strategy in the DWT domain. The proposed method is blind in the sense that only a secret key, if any, and the size of the original DEM are needed to extract the data from the texture image. We believe that this is one of the pioneering methods to propose scalable embedding of DEM in the texture image. The method is cost effective, in terms of memory and bandwidths, which is an advantage, especially, in real-time environments when quicker transfer of data is required. The results of a 3D visualization simulation effected with our method were encouraging and gave a useful insight to the effectiveness of our method in various bandwidth scenarios.

International audience; In this paper, we present a novel attack named colorization attack. This attack is specific to color-hiding watermarking schemes. The objective of this work is to demonstrate the feasibility of such an attack and thus to take it into account for the future color-hiding watermarking schemes.

International audience; Since several years, the protection of multimedia data is becoming very important. The protection of this multimedia data can be done with encryption or data hiding algorithms. To decrease the transmission time, the data compression is necessary. Since few years, a new problem is trying to combine in a single step, compression, encryption and data hiding. So far, few solutions have been proposed to combine image encryption and compression for example. Nowadays, a new challenge consists to embed data in encrypted images. Since the entropy of encrypted image is maximal, the embedding step, considered like noise, is not possible by using standard data hiding algorithms. A new idea is to apply reversible data hiding algorithms on encrypted images by wishing to remove the embedded data before the image decryption. Recent reversible data hiding methods have been proposed with high capacity, but these methods are not applicable on encrypted images. In this paper we propose an analysis of the local standard deviation of the marked encrypted images in order to remove the embedded data during the decryption step. We have applied our method on various images, and we show and analyze the obtained results.

International audience; In this paper a novel reversible method for fast and safe image transfer is proposed. The method combines compression, data hiding and partial encryption of images in a single processing step. The proposed approach can embed data into the image according to the message size and partially encrypt the image and the message without changing the original image content. Moreover, during the same process the image is lossless compressed. Nevertheless, the compression rate depends on the upper bound of message size to embed in the image. The main idea is to decompose the original image into two sub-images and to apply various processes to each sub-image in order to gain space and increase the amount of embedded data. The two sub-images are then scrambled and partially encrypted. The most significant characteristic of the proposed method is the utilization of a single procedure to simultaneously perform the compression, the reversible data hiding and the partial encryption rather than using three separate procedures. Our approach reduces then the computational effort and the required computation time. This method is specially suited for medical images where one can associate the patient diagnostic to the concerned medical image for safe transfer purpose.

International audience; In this paper, we propose a method to protect faces in videosurveillance scenes. Our method deletes any visible information of faces in a video and uses a data-hiding technique to embed information in the video that allows further reconstruction of the faces if needed. When the entire information needed for reconstruction is embedded, we obtain infinite PSNR for the face regions.

International audience; In this paper, we propose a method to embed the color information of an high dimension image in its corresponding grey-level image. The objective of this work is to allow a free and rapid access to the grey-level image and give color image access to secret key owners. This method is made of two steps which are the fast high-dimension color image decomposition (in a grey-level image and its associated color information) and the data-hiding. The two main contributions of this paper are the energy function proposed to model the decomposition of the color image and the fast optimization. The optimization of the proposed energy function leads to the achievement of an index image and a color palette. The good properties of that decomposition are an index image which is similar to the luminance of the color image and a color palette which is well suit for the data-hiding. The obtained results confirm the model quality and the real-time property.

International audience; This paper addresses the protection of images. We address the problem of simultaneous selective encryption (SE) and image compression. The SE is done by using the Advanced Encryption Standard (AES) algorithm with the Cipher Feedback (CFB) mode one a part of the Huffman coefficients corresponding to the AC frequencies. For the compression we consider the JPEG algorithm. Our approach is done without affecting the compression rate and by keeping the JPEG bitstream compliance. In the proposed method, the SE is performed in the Huffman coding stage of the JPEG algorithm without affecting the size of the compressed image. We provide an experimental analysis of the proposed method when applied on still images as well as the results when applying SE in JPEG compressed images.

International audience; This paper deals with face tracking in difficult conditions of non calibrated camera, strong head motions, thanks to a deformable 3D model. In those conditions, the proposed approach is able to detect and track a face. The novelty is mainly due to a multi-resolution Active Model search which allows to catch strong head motions. Results show an improvement between the single and the multi-resolution technique. Near real-time results are also provided.

International audience; In this paper, we propose a method to embed the color information of an image in a corresponding grey-level image. The objective of this work is to allow free access to the grey-level image and give color image access only if you own a secret key. This method is made of three major steps which are a fast color quantization, an optimized ordering and an adapted data hiding. The principle is to build an index image which is, in the same time, a semantically intelligible grey-level image. In order to obtain this particular index image, which should be robust to data hiding, a layer running algorithm is proceeded to sort the K colors of the palette. The major contributions of this paper are the fast color quantization, the optimized layer running algorithm, the color palette compression and the adapted data hiding.

International audience; The use of aerial photographs, satellite images, scanned maps and digital elevation models necessitates the setting up of strategies for the storage and visualization of these data in an interactive way. In order to obtain a three dimensional visualization it is necessary to map the images, called textures, onto the terrain geometry computed with Digital Elevation Model (DEM). Practically, all of these informations are stored in three different files: DEM, texture and geo-localization of the data. In this paper we propose to save all this information in a single file for the purpose of synchronization. For this, we have developed a wavelet-based embedding method for hiding the data in a color image. The texture images containing hidden DEM data can then be sent from the server to a client in order to effect 3D visualization of terrains. The embedding method is integrable with the JPEG2000 coder to accommodate compression and multi-resolution visualization.

International audience; In this paper, we propose a method to embed the color information of an image in its corresponding grey-level image. The objective of this work is to allow free access to the greylevel image and give color image access to secret key owners. This method is made of two steps which are the color image decomposition (in a grey-level image and its associated color information) and the data-hiding. The main contribution of this papper is the energetic function proposed to model the decomposition of the color image. The optimization of the proposed energetic function leads to the obtention of an index image and a color palette. The good properties of that decomposition are an index image which is similar to the luminance of the color image and a color palette which is well suit for the data-hiding. The obtained results confirm the model quality.

International audience; In this paper we present a new algorithm to track an organ in a sequence of medical images in order to achieve a 3D reconstruction. The automatic method that we propose allows the tracking of the external contour of the anatomical organ in all the sequence from one contour initialized by the user on the first image. The required operations for our tracking method are the region-based active contours segmentation. The objects localization with dynamic prediction of displacements is based on the level-set functions and the definition of the region of interest for the robust local estimation of the image model. An application of this method is the 3D reconstruction of abdominal aorta.

International audience; Using aerial photography, satellite imagery, scanned maps and Digital Elevation Models implies to make storage and visualization strategy choices. To obtain a three dimensional visualization, we have to link these images called texture with the terrain geometry named Digital Elevation Model. These information are usually stored in three different files (One for the DEM, one for the texture and one for the geo-referenced coordinates). In this paper we propose to store these information in only one file. In order to solve this problem, we present a technique for color data hiding of images, based on DC components of the DCT-coefficients. In our application the images are the texture, and the elevation data are hidden in each block. This method mainly protects against JPEG compression and cropping.

International audience; Verification of a document legitimacy is a current important problem. In this paper we propose to use a textured image containing a visual message, which can be used for identification of differences between printed legitimate document and printed fake document. The suggested textured image consists of specific patterns which should satisfy particular conditions in order to give good recognition results after Print-and-Scan (P&S) process. The identification of a legitimate document is possible by correlating the patterns of the textured image with either the original patterns or representative P&S process patterns. Several experimental results validate the proposed verification method.

International audience; In an increasing number of image and video processing problems, cryptographic techniques are used to enforce content access control, identity verification and authentication, and privacy protection. The combination of cryptography and signal processing is an exciting emerging field. This introductory paper gives an overview of approaches and challenges that exist in applying cryptographic primitives to important image and video processing problems, including (partial) content encryption, secure face recognition, and secure biometrics. This paper aims to help the community in appreciating the utility and challenges of cryptographic techniques in image and video processing.

International audience; In this paper we propose an approach for monitoring human activities in an indoor environment using detected and tracked face and selective encryption. The objective is to encrypt partially the human face in a video sequence. This approach is based on AES stream ciphering using VLC (Variable Length Coding) of the Huffman's vector. The proposed scheme allows scalable decryption of a specific region of image and result in a significant reduction in encrypting and decrypting processing time. It also provides a constant bit rate and keep the JPEG and MPEG bitstream compliance.

International audience; This paper presents a new decoder for probabilistic binary traitor tracing codes under the marking assumption. It is based on a binary hypothesis testing rule which integrates a collusion channel relaxation so as to obtain numerical and simple accusation functions. This decoder is blind as no estimation of the collusion channel prior to the accusation is required. Experimentations show that using the proposed decoder gives better performance than the well-known symmetric version of the Tardos decoder for common attack channels.

International audience; The data needed for 3D terrain visualization consists, essentially, of a texture image and its corresponding digital elevation model (DEM). A blind data hiding method is proposed for the synchronous unification of this disparate data whereby the lossless discrete wavelet transformed (DWTed) DEM is embedded in the tier-1 coded quantized and DWTed Y component of the texture image from the lossy JPEG2000 pipeline. The multiresolution nature of wavelets provides us the scalability that can cater for the diversity of client capacities in terms of computing, memory and network resources in today's network environment. The results have been interesting and for a bitrate as low as $0.012$ bit per pixel (bpp), a satisfactory visualization was realized. We compare the obtained results with those of a previous method that interrupt the lossless JPEG2000 codec immediately after the DWT step and embeds lossless DWTed DEM in the reversibly DWTed Y component of texture. The proposed method proved to be more effective in the sense that for the same bitrate one observed lesser quality loss for respective resolutions.

International audience; In this study we propose a new approach for selective encryption in the Huffman coding of the Discrete Cosine Transform (DCT) coefficients using the Advanced Encryption Standard (AES). The objective is to partially encrypt the human face in an image or video sequence. This approach is based on the AES stream ciphering using Variable Length Coding (VLC) of the Huffman's vector. The proposed scheme allows the decryption of a specific region of the image and results in a significant reduction in encrypting and decrypting processing time. It also provides a constant bit rate while maintaining the JPEG and MPEG bitstream compliance.

International audience; This research paper describes a new method in which the discovery and construction of man-made structures, specifically medieval castles, in a three dimensional environment can be intelligently constructed given only a random terrain and simple user-defined ...

We propose an efficient lossless compression scheme for still images based on arithmetic coding. The scheme presents a novel adaptive arithmetic coding that updates the probabilities of pixels only after detecting the last occurrence of each pixel and then removes the redundancy from the original image effectively. The proposed approach has interestingly low computational complexity. In addition, unlike other statistical coding techniques, arithmetic cod- ing in the proposed scheme is not solely dependent on the pixel probability distribution but also on the image block sorting. The pro- posed method is compared to both static and adaptive order-0 mod- els while taking into account compression ratios and processing time. Experimental results, based on a set of 100 gray-level images, demonstrate that the proposed scheme gives mean compression ratios that are 5.5% higher than those by the conventional arithmetic encoders as well as significantly faster than the order-0 adaptive arithmetic coding. © 2010 SPIE and IS&T. DOI: 10.1117/1.3435341