Opaque Document Imaging: Building Images of Inaccessible Texts

Yun Lin, W. Brent Seales

Abstract: This paper introduces a method for building a readable image of an opaque, rolled or folded text from a volumetric, penetrating scan. The problem is framed by localizing, constructing, and manipulating an image induced by a surface embedded in a 3D voxel space. There are two central contributions that lead to the demonstrated results. First is an energy-based texture formation algorithm, which is a function of voxel intensities and the geometry of the embedded surface. Second is a regularization algorithm based on a constrained mapping of the embedded surface to a regularized image plane. The mapping preserves angles and lengths, which minimizes the distortion of text in the image. The experimental results show readable images derived from custom, high resolution (X-ray-based) CT scans of rolled papyrus and ink samples. These methods are significant for scholars seeking to study inaccessible texts, and may lead to viable techniques for scanning everyday opaque objects (books) without opening them.