jaconv
Japanese character conversion library
japanese-string-utils
The utils convert Japanese strings to other forms, such as Hiragana, Katakana, Full-width, Half-width, numeric and others.
hanzen
UTF-8 halfwidth katakana interconversion functions
japanese-fullhalf-convert
Convert Japanese characters between full-width (全角) and half-width (半角) including Katakana, numbers, and punctuation
henkaku
Functions to convert UTF-8 characters between full-width 全角 and half-width 半角