## 3 Datasets
### Annotated Page Elements  
For the reconstruction of the reading order, the line-level layout analysis should detect all elements, which must be treated differently than concatenating lines from left to right and top to bottom. Such elements are header and footer lines and marginalia on either the left or right side, which are not part of the reading order. Furthermore, a two-column layout of the text must be recognized. Headlines do not influence the reading order. Therefore, they were treated as text, but they can be differentiated by a postprocessing step based on the font style and size and the centered layout if necessary. Images can be ignored, but a special image type must be recognized: dropped capitals look like an image in some cases, but semantically represent a letter. Therefore, we annotated the corpora with six categories. Figure 1: Example images from the datasets used. Top row (from left to right): CamStd, CamMarg; bottom row (left to right): GW5051, GW5056. **Text:**  
These elements describe the main text elements that should be included in a running text representation of a historical print. In order to generate the running representation, the OCR of the text elements should be concatenated in vertical order. **Text in columns:**  
As some pages contain multiple columns of text, the reading order must be adjusted. Therefore, it is important to differentiate these lines from regular text lines, as the text in columns should be read in the column-first order. **Marginalia:**  
In many historical prints, marginalia are printed on the left or right of the main text lines. Such marginalia might contain additional notes, references to the original, or line numbers. They may be viewed as a correlate for modern footnotes. They do not belong to the reading order of the normal text, but should be recognized as text and attached to the corresponding text line. **Header:**  
On many pages, headers containing the name of the chapter or the print, as well as page numbers are included. They help maintain an overview ofthe book and should not be included in the main running text representation and the reading order. There is no differentiation between further semantic types, such as page numbers, folio number, etc., because this is best performed based on the result of the OCR step, which was not the focus of this paper. **Footer:**  
Similar to header elements, footer elements such as catchwords or signature marks should not count as the main text and be excluded from the reading order. Similar to header elements, footer elements are not split into their different sub-categories, but are merged into a single line polygon. Figure 2: Example images from the CamManual dataset. The left images show difficult dropped capitals, complex footers, and marginalia consisting of single letters representing zodiac signs. The right image shows a page containing handwritten artifacts such as underlines. Dropped capitals:  
Dropped capitals are usually found at the beginning of paragraphs and usually represent the first character or word of the first line of said paragraph. Dropped capitals are printed larger, often spanning multiple lines of text, which is thereby indented, and are often decorated. Therefore, even if they technically are the first letter of a text line, it is disadvantageous to include them in said line, as they significantly differ in size and visual appearance and, therefore, would constitute a challenge for the subsequent OCR. Figure 3 shows these elements on two example pages from our used datasets. In addition to the above-mentioned elements, historical prints might also contain images. These are also annotated in the GT and, thus, included in our evaluation, as these elements could falsely be detected as text elements. However, the proposed method does not detect image regions, as it was designed for text element extraction.