A Pen Based Formula Entry System

A complete user interface for equation editing has been developed, using the recognition and parsing modules described earlier. The interface allows handwritten entry of mathematical formulae, correction of errors made in the automatic interpretation of what the user enters, and basic equation editing.

  

Figure 4.2: A formula that has been entered into, and parsed by, the system.

Formulae can then be parsed to determine the L^ATEX command string to generate them, and the result is automatically passed through external tools to generate a preview. Figure 4.2 shows a screenshot of the system. The formula has been written in by the user, and parsed by the system which then presents a typeset result. The user is able to copy the L^ATEX code from the entry area at the top of the preview window and insert it into their L^ATEX document.

The remainder of this chapter describes the new system created. The user interface controlling routines are written in Tcl/Tk. The parser, character recogniser, and stroke grouping routines are written in C and C++. All implementation was done on a 180MHz Intel Pentium Pro based system, running X-Windows under Linux.

Each of the elements used to make the final system would be greatly improved if they were able to take advantage of contextual information. Using contextual information has been a focus of research in formula recognition . However, even with higher level information and improvements in character recognition systems, errors are still possible. Knowing this, designing an interface that simplifies the correction of such errors is important.

. However, even with higher level information and improvements in character recognition systems, errors are still possible. Knowing this, designing an interface that simplifies the correction of such errors is important.