Tesseract is a commercial quality OCR engine originally developed at HP between 1985 and 1995. In 1995, this engine was among the top 3 evaluated by UNLV. It was open-sourced by HP and UNLV in 2005. You will need to get one of the language packs in order to do anything useful with tesseract, and that language pack tarball should be present in the same directory as the SlackBuild script when the package is created. See the website for a list of all available language packs. Note that you can install more than one (or even all) of the language packs, as they do not conflict with each other. The build script defaults to use English, but this is easily changed by passing an alternate value on the command line: edit the LANGNAM variable to switch to (or add) another language.