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