[planteen]

Is there a simple algorithm for Latin letters to Arabic ones (meaning logic input letters, not shaped ones)? Or are there lots of complexities? My understanding of the Arabic language is that most vowels are omitted in writing, but that might be wrong.

[schoen]

It would have to depend on what language you're trying to transliterate, because the phonetic meaning of the Latin letters is different depending on the language they're used to represent (and for many languages, depending on the particular word). For example, ti- will usually be /tʃi/ in Brazilian Portuguese and /tɪ/ in English. Typically each orthography is specific to a language and a script doesn't encode sounds in a consistent language-independent way, so you have to know something about both the source and target languages to devise a transliteration system.