Interactive Exploration and Flattening of Deformed Historical Documents

Abstract

Figure 1: From left to right: A 3D reconstruction of a damaged parchment, a global flattening of the parchment, a locally-affine undistortion of a section of the text, and a local flattening of that same section. AbstractWe present an interactive application for browsing severely damaged documents and other cultural artefacts. Such documents often contain strong geometric distortions such as wrinkling, buckling, and shrinking and cannot be flattened physically due to the high risk of causing further damage. Previous methods for virtual restoration involve globally flattening a 3D reconstruction of the document to produce a static image. We show how this global approach can fail in cases of severe geometric distortion, and instead propose an interactive viewer which allows a user to browse a document while dynamically flattening only the local region under inspection. Our application also records the provenance of the reconstruction by displaying the reconstruction side by side with the original image data.

Content‐aware surface parameterization for interactive restoration of historical documents

“…The templates are generated by manually extracting a number of examples of such characters from the parchment data set and aligning and blending them together. On a new parchment, characters are detected by automatically extracting roughly aligned patches of text at various locations on the parchment surface, using an approach similar to [PTW13b]. For each patch and character template, we compute the normalized cross correlation response image, identifying peaks as matches.…”

“…[PCCS11] flattens user‐selected rectangular surface strips of a 3D surface, using a parametrization based on an underlying cross field, enabling the analysis of the high‐frequency details of the corresponding texture. Similarly, the problem is tackled in [PTW13b] with an interactive local approach. A text direction field is automatically computed and is used to drive an interactive document browser in which local regions of a document can be flattened individually.…”

“…This effect can be seen in Figure 3. Local methods [PTW13b] are successful in flattening individual regions, but are not able to restore the entire document. The rationale for applying a local parametrization strategy is that, for small regions of the surface, it is always possible to find a low distortion parametrization that makes the analysis of the text easier.…”

Contrast in Terahertz Images of Archival Documents—Part II: Influence of Topographic Features

“…5d is the only image in which the handwritten inscriptions become at least partially legible. In practice, documents are not perfectly flat, and in the case of water-or fire-damaged documents, they can have a very irregular and curved surface [15]. For this study, the sheets were held taut and flat by placing them between two ring-shaped magnets.…”

A Book Reader Design for Persons with Visual Impairment and Blindness

“…The concepts of de-warping and flattening have also been explored in applications that include the restoring and enhancement of historical documents [41,42], and for recognizing street signs from 3D scenes [43]. Cylindrical surface modeling has also been considered through the use of an isometric mesh [44] or through optical flow and structure from motion, by using the camera of a mobile phone, which is swept across the book spread for image capture [45].…”