ExactImage is an image processing library which reimplements
ImageMagick functions with a significant speed improvement.
The library also provides several new algorithms: lossless JPEG
transforms and creation of searchable PDFs from hOCR annotated HTML
created with an OCR program such as Tesseract or Cuneiform (available
at Slackbuilds.org). There are bindings for PHP[*], Lua, Perl, and
Python. See /usr/doc/exact-image-*/examples/ for information on using
exactimage with Perl, Python, PHP[*] and Lua.

lua is an optional dependency.

bardecode is also optional but not available at SBo.

[*] The PHP extension is disabled in this SlackBuild, as it only
    supports PHP5, and we have PHP7 on Slackware 15.0. Sorry.