There's also https://scantailor.org/ https://scantailor.org/ (and a maintained fork at https://github.com/4lex4/scantailor-advanced https://github.com/4lex4/sc

There's also https://scantailor.org/ https://scantailor.org/ (and a maintained fork at https://github.com/4lex4/scantailor-advanced https://github.com/4lex4/scantailor-advanced ) which semi-automates unwarping and other corrective tasks in scanned books.