Extracting Mathematical Components Directly from PDF Documents for Mathematical Expression Recognition and Retrieval

PDF document gains its popularity in information storage and exchange. With more and more documents, especially the scientific documents, available in PDF format, extracting mathematical expressions in PDF documents becomes an important issue in the field of mathematical expression recognition and retrieval. In this paper, we proposed a method of extracting mathematical components directly from PDF documents rather than cooperating indirectly with corresponding images converted from PDF files. Compared with traditional image-based method, the proposed method makes full use of the internal information of PDF documents such as font size, baseline, glyph bounding box and so on to extract the mathematical characters and their geometric information. The experimental result shows the method could meet the needs of the following processing of mathematical expressions such as formula structural analysis, reconstruction and retrieval, and has a higher efficiency than traditional image-based ways.