Preserving Cultural Heritage

The Journal of Electronic Imaging special section.

01 April 2017
Aladine Chetouani, David Picard, and Filippo Stanco

Affordable imaging devices, novel imaging techniques, and powerful image-processing algorithms have made image-related investigative tools very popular within the interdisciplinary field of cultural and historic preservation, and even among those outside the scientific community.

In particular, the problem-solving capabilities of image-related science — from data acquisition, processing, and analysis to data visualization and reconstruction — have had a tremendous impact on the soaring number of images acquired in cultural institutions and used in cultural heritage projects.

The growth and exploitation of images and their data have now introduced a feedback loop by uncovering new problems waiting to be solved by the optics and photonics community.

Designing practical algorithmic solutions will potentially have a tremendous impact on cultural heritage applications. To focus on this emerging field in which images are used as principal data to solve cultural heritage problems, the SPIE Journal of Electronic Imaging published a special section on image processing for cultural heritage in the January/February issue.

The special section includes 27 interesting papers tackling image-processing techniques for this field. These solutions span the entire field from novel imaging modalities to image retrieval and 3D reconstruction to automatic labelling. In that sense, the special section represents a good overview of the wide diversity of problems in cultural heritage applications on which imaging scientists could help improve the current state of the art.

In “Combination of image descriptors for the exploration of cultural photographic collections,” Neelanjan Bhownik, a PhD student at Université Paris-Est, and coauthors discuss the challenges of managing large volumes of digital images in museums and other cultural photographic collections. The authors describe and evaluate methods to easily archive and retrieve images for an exhibition and propose an image search engine they used with three public datasets (with various scene types, including Paris and Oxford landmarks).

Another article in the special section, “Hyperspectral imaging as a technique for investigating the effect of consolidating materials on wood,” presents a comprehensive study of imaging techniques used in identifying wood finishes. Giuseppe Bonifazi of Sapienza University of Rome and coauthors applied several consolidants (epoxy resin, acrylic resin, linseed oil, etc.) to a set of wood samples that were then artificially aged.

Since many cultural artifacts are made of wood, preservation of the wood’s surface characteristics, including texture and color, is crucial during restoration. Using hyperspectral measurements, the paper first presents an analysis of the effect of the different consolidants on the reflectance before and after aging. The paper also discusses a classification method able to distinguish between the consolidants using hyperspectral data.

Using the iterative closest point (ICP) algorithm for the first alignment in the image reconstruction of the historic Market Square in Calw, the figure on top shows the coarse point clouds from imagery (a) while the figure below shows the terrestrial laser scanner (TLS) point clouds.

The paper “Four-dimensional reconstruction of cultural heritage sites based on photogrammetry and clustering” presents a complete system for the efficient 4D modeling and presentation of cultural heritage sites. The international team of authors from Greece, Germany and Austria developed two approaches with complementary benefits: content-based filtering and photogrammetry precision.

They proposed the concept of “change history maps” to address the computational limitations involved in 4D modeling, i.e., capturing 3D models of a cultural heritage landmark or site at different times.

The described methods have been successfully applied and evaluated in challenging real-world scenarios, including the 4D reconstruction of the historic Market Square of the German city of Calw.

The papers are published in the Journal of Electronic Imaging.

–Aladine Chetouani of University of Orléans (France), David Picard of École Nationale Supérieure de l’Électronique et de ses Applications (France), and Filippo Stanco of Universita degli Studi di Catania (Italy), along with Robert Erdmann of University of Amsterdam, were guest editors of the special section in the Journal of Electronic Imaging.

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