The Jochre Alto4 editor is a graphical browser-based editor of Alto4 OCR layers, useful for constructing an Alto4 training corpus.
It is a pure client-side application: all you need to do is open the index.htm file in your browser.
It is designed for printed pages (rather than manuscripts).
It supports both left-to-right and right-to-left alphabets.
After cloning the repository, copy the config-local-template.js file into config-local.js, and change it to match your needs.
Also, copy the local-template.css file to local.css and change it to match your needs. You can override any settings from default.css.
When finished, open the index.htm file in your browser.
More information can be found in the design document and wiki.