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Modify Characters

No matter how good the underlying character recogniser is, errors in the recognition of symbols are still going to occur. The modify character mode allows the user to click on a misrecognised symbol's shaded bounding box and select from a pop up menu the correct interpretation for that symbol. The pop up menu contains the best choices, currently the top five, supplied by the character recogniser for that grouping of strokes. If there are repeated symbols in the top five, due to the fact that the character recogniser is able to recognise multiple styles for individual symbols, all but one of the occurrences are removed. Should the character that the user desires not appear on this pop up menu, the user may chose an enter option, and type the correct character from the keyboard. Symbols that do not appear on the keyboard are entered using a long-hand name. For example, ``$\Sigma$'' is entered ``Sigma''. The user is also able to choose non-keyboard systems from a toolbar.

Figure 4.7: Correcting a misrecognised character.
(a) Initial interpretation.
(b) Selecting the correct interpretation from the pop up menu.
(c) The corrected character.

Figure 4.7 shows a user correcting a misrecognised character in modify character mode. The ``z'' in Figure 4.7(a) that the user drew was misrecognised as an ``2''. By clicking on the character a pop up menu appears, as shown in Figure 4.7(b). Selecting the correct choice from this menu then overrides the recogniser. Figure 4.7(c) shows the corrected character.

Even though the pop up menu correction method is easy and intuitive, users found the process of correcting character interpretation errors somewhat tedious if the correct alternative was not on the pop up menu. Having to resort to manually entering the character is distracting as it requires that the user switch from using the pen to using the keyboard. High character recognition rates are therefore very important, and any serious user of the system must take the time to train the recogniser with their own handwriting.

next up previous
Next: Parsing and Preview Up: A Pen Based Formula Previous: Stroke Regrouping
Steve Smithies