of the Mona Lisa by Leonardo da Vinci. A. Pelagotti, A. Del Mastio, A. De Rosa, and A. Piva propose a novel multispectral digital imaging technique that, with a.
[from the GUEST EDITORS]
Mauro Barni, Jean-Angelo Beraldin, Christian Lahanier, and Alessandro Piva
Signal Processing in Visual Cultural Heritage
T
he application of signal processing to the analysis of visual cultural heritage, such as films, photographs, paintings, sculptures, archaeological sites, historical monuments, ethnographic collections, and natural history specimens, is uncommon amongst both conservators and information and communication technology (ICT) specialists. In recent years, there has been greater interest in the acquisition, processing, storage, transmission, representation, analysis, and presentation of cultural-heritage-related image data. International efforts in these areas have demonstrated promising results from both high-visibility projects and an ever-growing number of local initiatives. The purpose of individual projects is highly varied and may include material analysis (dating and provenance determination), discovery and interpretation of ancient technologies, examination of details (tool marks, brush strokes, craquelure), exploration of artists’ environment and mutual relationships, enhanced knowledge of conservation materials and processes, and cultural heritage dissemination and presentation. In all cases, digital signal processing is the foundation upon which these applications must rely in order to deliver both optimal and highly repeatable results. This special section of IEEE Signal Processing Magazine is aimed at the dissemination of the most recent advances in signal processing applications to visual cultural heritage. Recent interest in this topic by both conservators and ICT specialists has been demonstrated through the large number of white papers submitted in Digital Object Identifier 10.1109/MSP.2008.923976
response to our call for proposals. The editors had the difficult task of limiting the number of articles due to space constraints. Articles were selected based on their academic content and the need to have a well-balanced special section demonstrating different aspects of signal processing for visual cultural heritage. The editors have grouped the articles into three research themes: multispectral imaging, artwork analysis, and three-dimensional (3-D) digitization and modeling. The first two articles investigate the application of multispectral imaging to artworks. A. Ribés, R. Pillay, F. Schmitt, and C. Lahanier present a tutorial on the signal processing issues related to the acquisition of multispectral images. Problems concerning the design of multispectral cameras, their calibration, and the processing of the resulting data are analyzed in the context of digitization of paintings. The authors describe the practical acquisition of multispectral images of the Mona Lisa by Leonardo da Vinci. A. Pelagotti, A. Del Mastio, A. De Rosa, and A. Piva propose a novel multispectral digital imaging technique that, with a fairly simple imaging system, concurrently analyzes three different imaging modalities. The method allows the clustering of image regions within a set of images that show similar reflection, absorption, and emission of electromagnetic radiation. By utilizing signatures from the material’s molecular composition and shape to provide material localization and identification over the complete surface of a painting. The third and fourth articles of the issue deal with the problem of artwork analysis and artist identification. C.R. Johnson, Jr., E. Hendriks, I. Berezhnoy, E. Brevdo, S. Hughes, I. Daubechies, J.
IEEE SIGNAL PROCESSING MAGAZINE [10] JULY 2008
Li, E. Postma, and J. Wang describe studies on brushwork analysis and artist identification developed by three research groups. This work is the result of analysis of a common data set of 101 high-resolution gray-scale scans of paintings within the collections of the Van Gogh and Kröller-Müller Museums in The Netherlands. After a description of brushwork characteristics used by art historians for authentication purposes, the results achieved by the image analysis groups are analyzed. H. Leung, S.T.S. Wong, and H.H.S. Ip present an article on the preservation of ancient Chinese calligraphy. In particular, they propose a methodology for Chinese calligraphy image analysis based on the estimation of the set of 3-D geometric parameters as well as the dynamic writing parameters such as the properties of brush hair and the variations of ink deposition along the stroke trajectory. Given a raw digitalized Chinese calligraphy image, the method allows the automatic determination of a brush model parametric representation. The last two articles of the issue are concerned with the 3-D digitization and modeling applied to heritage sites and objects. F. Remondino, S.F. El-Hakim, A. Gruen, and L. Zhang present advanced image-based techniques capable of capturing fine 3-D geometric details of heritage sites and objects, which present a challenge to all existing 3-D techniques. A multistage procedure for 3-D data capture from images acquired with inexpensive portable digital cameras, designed to extract and model the fine geometric details, is proposed. The approach requires a limited amount of human interactivity and is capable of capturing fine geometric details with similar accuracy to close-range active range sensors. A.R. Willis and D.B.
[from the GUEST EDITORS]
continued
Cooper propose a survey of automatic and semiautomatic artifact reconstruction systems applied to real-world geometric puzzles like the fragments of complete relics discovered by anthropologists and archaeologists. Two leading approaches for two-dimensional tablet reconstruction and four leading approaches for 3-D object reconstruction are discussed. Several extensions to
[in MEMORIAM]
the geometric matching problem that use patterns apparent on the fragment outer surface are also discussed to generalize the problem beyond that of a geometry matching solution. We would like to thank all the authors involved in this special section as well as those who submitted excellent proposals that we could not consider for this issue. We are grateful to all review-
ers who did excellent work under strict deadlines. We also would like to thank Doug Williams, area editor for special sections, for his support and guidance. We hope that researchers involved in all aspects of signal processing will find in this special section useful information and the inspiration for further research and innovation in signal processing for [SP] visual cultural heritage.
Informa-tionstechnische Gesellschaft (ITG) and the Award for Basic Research of the Eduard-Rhein-Foundation. He was awarded honorary doctorate degrees by the Technical University of Munich and the Technical University of Vienna in 1994 and 1995, respectively. In 1990, he was elected a member of the Bavarian Academy of Science. He was awarded the IEEE Jack S. Kilby Signal Processing Medal in 2003 “for his role in the early development of the field of Digital Signal Processing, especially the theory, design, and implementation of analog and digital filters.”
Hans will be remembered for his profound belief in the international exchange of scientists. He promoted this cross-continental dialog tirelessly, both in his daily activities and in the establishment, with Helga, of the Schüßler Stiftung, the Hans-Wilhelm and Helga Schüßler Fund for International Research. Hans’ memory will continue to inspire and ensure a positive impact on the field of engineering communications and on the IEEE Signal Processing Society about which he cared so deeply. [SP]
continued from page 8
Hans was elected IEEE Fellow in 1977 for “contributions to the theory of analog and digital filters.” He received the Society Award of the IEEE Acoustics, Speech, and Signal Processing Society (later renamed the Signal Processing Society) in 1979 and the IEEE Centennial Medal in 1984. He was awarded the “Verdienstkreuz am Bande” of the Federal Republic of Germany in 1980 and the award of the Stichting Fund for Science, Technology and Research by the Schlumberger Company in 1986. In 1993, he received both the Karl-Küpfmüller Award of the German
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IEEE SIGNAL PROCESSING MAGAZINE [12] JULY 2008
