Connected Bond Recognition for Handwritten Chemical Skeletal Structural Formulas

Recognizing handwritten chemical structural formulas is challenging due to the spatial complexity involved, especially for chemical skeletal structural formulas. In chemical skeletal structural formulas, the Carbon atoms are omitted in the drawing of chemical connected bonds, in which the single bonds are connected with hidden Carbon atoms as the connection points. To recognize chemical skeletal structural formulas, it is important to recognize the connected bond strokes and differentiate them from other similar symbols. Moreover, even if the connected bond stroke is identified, it is also challenging to split the connected bond stroke into several single bonds and identify the locations of the hidden Carbon atoms, and its positional relationship in the overall chemical structure. In this paper, we propose a progressive approach for recognizing chemical skeletal structural formulas, in particular the connected bonds. The proposed approach recognizes a chemical formula progressively while the user draws the chemical skeletal structural formula.