Specifying an Alphabet Set

By supporting the following alphabet functions, a recognizer enables an application to specify which alphabet sets to consider during recognition. Alphabets are sets of characters within the entire range of characters the recognizer can interpret. For example, an application can limit recognition to any combination of lowercase characters, punctuation, math symbols, and so forth.

The Pen API defines ALC_ values to identify an alphabet set. For further information on alphabets and an abbreviated list of the most common ALC_ values, see "Configuring the HRC" in Chapter 5, "The Recognition Process." A full list of ALC_ values appears in Chapter 13, "Pen Application Programming Interface Constants."

The Pen API allows an application to set a priority when using multiple alphabet sets. Priority can resolve conflicts when one glyph has different interpretations in different alphabets. For example, consider a case in which input consists of both letters and numerals, but the application expects numerals more often. By setting an alphabet of ALC_ALPHANUMERIC and a priority of ALC_NUMERIC, the application tells the recognizer to consider both letters and numerals, but interpret for numerals first. This helps resolve the problem of distinguishing between the numeral "0" and the letter "O."

The following table lists the optional recognizer functions that pertain to alphabets.

Function	Description
GetAlphabetHRC	Retrieves bitwise-OR flags of ALC_ values indicating which alphabet(s) the recognizer can currently recognize.
GetAlphabetPriorityHRC	Retrieves bitwise-OR flags of ALC_values indicating priority.
SetAlphabetHRC	Constrains recognition to a specified set of alphabet characters.
SetAlphabetPriorityHRC	Specifies the priority of alphabets used during recognition.
SetBoxAlphabetHRC	Constrains recognition to a set of specified alphabet characters for individual boxes in a group of boxes.

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