I am also having a problem with subtitle workshop. I have subs in chinese and trying to translate them to english. their guide does not make any sense and it does not recognise the .idx and .sub subs I have with the movie. I used vobsub to try to convert them into a format that workshop can use, but it shows nothing. Is there a real program that can convert the language to english?
Converting from bitmap to text requires OCR'ing and Subtitle Workshop only supports text based formats. I guess you could OCR it, but instead of entering the Chinese characters, enter English. OCR'ing Chinese can't be easy though.