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... in digital imaging have resulted in massively increased image resolutions and bit depths as well as in new techniques such as 3D imaging and topographical scanning. These new imaging techniques produce enormous quantities of data that need to be adequately managed, handled and exploited. Apart from the sheer volume of data, other advanced features such as colorimetric accuracy, high dynamic ranges (e.g. 16 bit images) and multi-channel output must also be considered. This problem has been particularly acute at the research and restoration centre at the Louvre Museum (the C2RMF - Centre de Recherche et Restauration des Musées de France) where a diverse range of imaging technologies have been applied in order to assist curators, restorers and researchers. In order to view such data, standard visualisation systems that simply transfer and load an entire image into memory are very inefficient. Not only are the scans large, but also colour calibrated, meaning that colour management must also be handled. The use of these advanced technologies has limited value if their results cannot be easily used or widely exploited. A key technical challenge is, therefore, how to efficiently disseminate this high quality data to people both internally and externally of the research centre. In order to handle this diversity of extremely large images, the Open Source IIPImage[1] system is used. IIPImage is a client-server system designed for the remote viewing of very high resolution images across the Internet. Its architecture gives it the peculiarity to be usable even over a slow dial up connection. The server can be launched as a plug-in that can work with a wide variety of web servers such as: Apache, Lighttpd or MyServer or any other FCGI-enabled http server. Images can be viewed via a feature-rich Java client, a Javascript client embedded within a web page or as JPEG image dynamically generated at the requested size and resolution by the server [2,3]. The system evolved from a prototype used in several European projects to view high resolution images of works of art across the Internet and has been greatly extended and restructured to handle the new imaging techniques described later in this paper. The system is fast and able to work remotely because the client only needs to download the portion of the whole image that is visible on the screen of the user at their current viewing resolution (Fig. 1). This means that it is also bandwidth and memory efficient as users do not need to be able to store or handle massive images on their local machine. Only the required parts of the whole image at the desired resolution need be sent. The image tiles at the requested resolution are extracted from the source file by the server, dynamically compressed with JPEG (or lossless if desired) and sent to the client. The compression level used can be controlled by the client to optimize the transmission depending on the network environment (Fig. 2). This technique makes it possible to view extremely large images of several gigabytes in size in real-time over the Internet. In order for the system to be as efficient as possible, the images are stored in a multi-resolution tiled format, (Fig. 3) which allows the server to extract regions of the full image at different resolutions very quickly with little processing overhead. Although a proprietary file format such as Flash Pix could have been used or a new one especially developed, it was decided to keep the format as open and interoperable as possible. The TIFF format is widely used and is flexible enough to permit this kind of structuring and encoding. Multiple resolutions can be stored within a single file in a pyramid-like structure using the standard TIFF multi-page functionality and each resolution can be tiled. A pyramidal image without compression uses only 33% extra space. However, the tiles can be optionally compressed using either a lossless compression such as Deflate or LZW, or a lossy compression such as JPEG. If space is an issue, JPEG compression is able to reduce the image file size by at least a factor of ten without a significant loss in visual quality [4]. When there are multiple views (e.g. multiple wavelengths or view angles etc), the different images are simply kept as separate files. The classical 8-bit RGB colour space most commonly used today is insufficient for the richness of data acquired by high resolution cameras such as the CRISATEL [5] camera. Colour images are, therefore, stored in the device-independent CIELab colour space, which is able to describe colours that are outside the gamut of RGB. Furthermore, higher dynamic ranges (16-bit) are required to store the full dynamic range of imaging detail that would be invisible or saturated using only 8-bits. The IIPImage system is flexible enough to handle standard 8-bit RGB images, higher dynamic range 16bit images as well as colour spaces such as CIELab and generic multispectral images. Standard monitors are only able, however, to display 8-bits of information per pixel per channel in RGB colour space. In order to visualize 16-bit or CIELab images, the raw data needs to be first processed. In the case of 16-bit images, a contrast control allows the user to navigate within the extra, normally hidden data. For CIELab images, a dynamic conversion is performed by the client into the calibrated RGB space of the monitor. Eventually, it will be possible to use ICC profiles to calibrate the image to the user's monitor. The same group that in 1997 created the FlashPix image format, developed, at the same time, the IIP (Internet Image Protocol), a protocol aimed at Internet-based imaging and optimized for the FlashPix format. The tiled pyramidal TIFF format used by us is similar to the FlashPix standard, but is a widely-used open format and is fully compatible with the protocol. The IIP protocol also allows for a certain amount of customisation which has allowed us to enhance certain features and add panoramic viewing, multispectral and surface topographic height handling to it. One of the advanced technologies used at the C2RMF is the multispectral CRISATEL camera system. Multispectral imaging enables us to accurately evaluate the surface physical state of a work of art. Having an accurate spectral record of the painting allows conservators to locate areas that may be invisible to the naked eye (Fig. 4) or that have been restored or retouched long ago[6]. By making regular scans of works of art, the gradual changes in the physical condition can be monitored and damage addressed quickly. The characterisation of materials used, the evaluation of the conservation state, the localization of previous restoration interventions and continuous monitoring are among the most important topics in the field of study and conservation of artworks. Another important imaging technique at the C2RMF arsenal is colorimetric 3D panoramic imaging. 3D imaging of objects and paintings offers a powerful new analytical tool to conservators, curators and art historians. High- resolution 3D image data contains information that can be used for display, comparison, measurement and ana– lytical applications. A large collection of statues and objects has been scanned using the ACOHIR system [8]. These consist of a sequence of images of an object on a rotating turntable taken with a standard RGB camera. The turntable has ...
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... Another solution is polynomial texture maps (PTMs), an extension of conventional texture maps. 14 15 aim to offer high resolution images (greater than the maximum resolution allowed by human vision) and tonal control in wide gamut spaces, such as CIELab. However, the absence of the third dimension limits the visualisation of the mesostructure; large files are generated, which are hard to manage on consumer devices by unskilled operators, and a problematic image stitching is required. ...
Colours play a crucial role in the field of architectural heritage. Colour analysis and colour rendition are involved in several critical facets of heritage preservation, conservation and restoration. These aspects are related to accurate documentation and an accurate representation of heritage artefacts and architectural works. The aim of this paper is to describe critical issues and open problems of the processes involved in this field. Documentation is performed in multiple ways, acquiring heterogeneous data ranging from archival images, photographs, drawings using various consumer or professional instruments (eg, digital cameras and spectrophotometers). The reliability of colour acquisition might be influenced by instrumental reasons (the technology used to acquire colour information), by environmental changes (architectural heritage surveys are often performed outdoors), by morphology (complex architectural objects are characterised by concavities and convexities which complicate the reflection evaluation), or by materials (showing different reflection, porosity and transparency indexes). Identification of materials, such as colorants, pigments and dyes, is also a vital process in the heritage field. Colour information could be used as an approach to the identification of materials, but these methods are still under development, and many issues need to be solved to achieve reliable results. Visualisation techniques of a heritage artefact also present the problem of the correctness of the colour representation. Several problems need to be faced in this context: the reliability of the acquisition, colour management of the rendering software, model complexity, and fragmentation of the devices upon which the model is visualised.
... An interactive visualisation of high-resolution hyperspectral data from the Russian icon has been developed and can be viewed online [32]. This facility uses the IIP-Image software suite [33] to provide interactive online access to a subset of the hyperspectral data. It features an image stack including a colorimetric CIE L*a*b* rendering of dataset B under a D65 illuminant and single frames at various specific wavelengths, which the user can select and smoothly blend between. ...
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Copyright © 2015. Published by Elsevier Inc.
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... The visualization of these images renders significant difficulty in a mobile device. An advanced image visualization server powered by an internet imaging protocol (IIP) and its HTML5-compatible viewer are built in the virtual Linux instance (Pitzalis et al. 2006). The stitched image, when completed by the image analysis service, will be converted into a tiled pyramidal tagged-image file format (TIFF) enabling web access with minimal overhead in mobile devices. ...
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... In France, the C2RMF laboratory, connected to the Louvre museum, has digitized more than 300, 000 documents taken from French museums, in high resolution (up to 20, 000 × 30, 000 pixels). The resulting EROS database [149] is for the moment only accessible to researchers whose work is connected with the C2RMF. To widely open the database, the idea is to create a framework to integrate the different security solutions in order to secure the access to the images. ...
This habilitation thesis is first devoted to applications related to image representation and coding. If the image and video coding community has been traditionally focused on coding standardization processes, advanced services and functionalities have been designed in particular to match content delivery system requirements. In this sense, the complete transmission chain of encoded images has now to be considered. To characterize the ability of any communication network to insure end-to-end quality, the notion of Quality of Service (QoS) has been introduced. First defined by the ITU-T as the set of technologies aiming at the degree of satisfaction of a user of the service, QoS is rather now restricted to solutions designed for monitoring and improving network performance parameters. However, end users are usually not bothered by pure technical performances but are more concerned about their ability to experience the desired content. In fact, QoS addresses network quality issues and provides indicators such as jittering, bandwidth, loss rate... An emerging research area is then focused on the notion of Quality of Experience (QoE, also abbreviated as QoX), that describes the quality perceived by end users. Within this context, QoE faces the challenge of predicting the behaviour of any end users. When considering encoded images, many technical solutions can considerably enhance the end user experience, both in terms of services and functionalities, as well as in terms of final image quality. Ensuring the effective transport of data, maintaining security while obtaining the desired end quality remain key issues for video coding and streaming. First parts of my work are then to be seen within this joint QoS/QoE context. From efficient coding frameworks, additional generic functionalities and services such as scalability, advanced entropy coders, content protection, error resilience, image quality enhancement have been proposed. Related to advanced QoE services, such as Region of Interest definition of object tracking and recognition, we further closely studied pseudo-semantic representation. First designed toward coding purposes, these representations aim at exploiting textural spatial redundancies at region level. Indeed, research, for the past 30 years, provided numerous decorrelation tools that reduce the amount of redundancies across both spatial and temporal dimensions in image sequences. To this day, the classical video compression paradigm locally splits the images into blocks of pixels, and processes the temporal axis on a frame by frame basis, without any obvious continuity. Despite very high compression performances such as AVC and forthcoming HEVC standards , one may still advocate the use of alternative approaches. Disruptive solutions have also been proposed, and offer notably the ability to continuously process the temporal axis. However, they often rely on complex tools (\emph{e.g.} Wavelets, control grids) whose use is rather delicate in practice. We then investigate the viability of alternative representations that embed features of both classical and disruptive approaches. The objective is to exhibit the temporal persistence of the textural information, through a time-continuous description. At last, from this pseudo-semantic level of representation, texture tracking system up to object tracking can be designed. From this technical solution, 3D object tracking is a logical outcome, in particular when considering vision robotic issues.
... From this particular kind of study, others have been initiated (Abas & Martinez, 2002, 2003, including use of the 'fuzzy' classification to recognise crack patterns. This problem has been particularly acute at the research and restoration centre at the Louvre Museum (the C2RMF -Centre de Recherche et Restauration des Musées de France) where a diverse range of imaging technologies has been applied to assist curators, restorers and researchers (Pitzalis et al., 2006;Pauchard et al., 2007). Another interesting research activity in image processing in the restoration sector has involved the visualisation of pigment distributions in paintings using synchrotron K-edge imaging (Krug et al., 2006). ...
This work aims to deal with the problem of identifying, analysing, and classifying cracks in figurative works. The recent, considerable progress made in techniques for processing visual information has broadened the number of scientific applications in which the display and graphic processing of data play a fundamental role. Cracks consist of many elements; distinguishing and studying them has made it possible to develop a classification that in some cases can also be used as tool to verify a work's authenticity. RESTART, the system presented here, is deemed suitable for use in numerous and varied settings, such as teaching, conservation, study and research. It is able to investigate, study, research and 'restore' the digital, in accordance with the criteria dictated by knowledge. Also of considerable interest is the investigation of a crack based on such characteristics as origin and pathology, and the possibility of analysing the cracks in a fresco. The use of RESTART for such case examples is investigated and proposed.
... In France, the C2RMF laboratory, connected to the Louvre museum, has digitized more than 300000 cultural items taken from French museums, in high resolution (up to 20000 × 30000 pixels). The resulting EROS database [5] is for the moment only accessible to art researchers whose work is directly connected with the C2RMF. The French TSAR project is designed to open the EROS database in a secure, efficient and user-friendly way that involves cryptography and watermarking as well as compression and region-level representation abilities. ...
... A mapping function was used on the metrics outputs, as recommended by the VQEG Multimedia TEST PLAN. This mapping function allows to rescale the objective measures to fit in the range of the MOS, which in the presented experiment is [1,5], as shown in Table 1. Once the mapping function computed for every quality metric, the predicted MOS (often referred to as the MOSp) may then be compared to the observers MOS. ...
... A subjective quality experiment was conducted specifically for LAR coded images on a set of eight input images, each being distorted at five compression rates. Nineteen observers with correct vision were enrolled and had to rate the quality of the distorted images on a [1,5] quality scale. Furthermore, five quality metrics were tested on the so obtained 40 distorted images. ...
Quality assessment is of major importance when designing and testing an image/video coding technique. Compression performances are usually evaluated by means of rate-distortion curves. However, the PSNR is commonly employed as the distortion measure. We hereby present a full quality assessment benchmark for the LAR (locally adaptive resolution) coder. We conducted a subjective experiment, where nineteen observers were asked to assess the perceptual quality of LAR coded images under normalized viewing conditions. Furthermore, five objective quality assessment metrics were used in order to determine the most suitable metric for the LAR coder. Finally, both JPEG and JPEG200 images were generated and assessed during the subjective experiment in order to define the optimal quality metric which should be used when comparing the codecs' output images quality.
... In France, the C2RMF laboratory, connected to the Louvre museum, has digitized more than 300, 000 documents taken from French museums, in high resolution (up to 20, 000 × 30, 000 pixels). The resulting EROS database [4] is for the moment only accessible to researchers whose work is connected with the C2RMF. In order to widely open the database, two problems have to be resolved. ...
... Five laboratories are involved, namely the C2RMF (Louvre, Paris), IETR (Rennes), IRCCyN (Nantes), LIRMM (Montpellier) and LIS (Grenoble). The C2RMF has developed the EROS (European Research Open System) database storing digital art documentation [4]. Till now, images have been stored in pyramidal TIFF format involving a bit overhead of 33%. ...
EROS is the largest database in the world of high resolution art pictures. The TSAR project is designed to open it in a secure, efficient and user-friendly way that involves cryptography and watermarking as well as compression and region-level representation abilities. This paper more particularly addresses the two last points. The LAR codec is first presented as a suitable solution for picture encoding with compression ranging from highly lossy to lossless. Then, we detail the concept of self-extracting region representation, which consists of performing a segmentation process at both the coder and decoder from a highly compressed image, and later locally enhancing the image in a region of interest. The overall scheme provides an efficient, consistent solution for advanced data browsing.
The role of museums and libraries is shifting from that of an institution which mainly collects and stores artefacts and works of art towards a more accessible place where visitors can experience heritage and find cultural knowledge in more engaging and interactive ways. Due to this shift, ICT have an important role to play both in assisting in the documentation and preservation of information, by providing images and 3D models about historical artefacts and works of art, and in creating interactive ways to inform the general public of the significance that these objects have for humanity. The process of building a 3D collection draws on many different technologies and digital sources. From the perspective of the ICT professional, technologies such as photogrammetry, scanning, modelling, visualisation, and interaction techniques must be used jointly. Furthermore, data exchange formats become essential to ensure that the digital sources are seamlessly integrated. This PhD thesis aims to address the documentation of works of art by proposing a methodology for the acquisition, processing, and documentation of heritage objects and archaeological sites using 3D information. The main challenge is to convey the importance of 3D model that is "fit for purpose" and that is created with a specific function in mind (i.e. very high definition and accurate models for : academic studies, monitoring conservation conditions over time and preliminary studies for restoration; medium resolution for on-line web catalogues). Hence, this PhD thesis investigate the integration of technologies for 3D capture, processing, integration between different sources, semantic organization of meta-data, and preservation of data provenance.
