GIMP has Script Fu (and a newer Python interface) which has been used for wonderfully time-saving things (e.g. process a thousand images with the same plugins and settings and such, implement your own custom processing tools by combining existing ones, etc.)

I'm sure the same sorts of things can be done with Krita, though I'm not familiar with it.

As for LibreOffice, that seems obvious. An easy/automated way to get data into and out of it for processing in other programs. An automated way to process lots of documents that need to stay in LibreOffice but need the same change performed on them (currency conversion, date format normalization, copyright update, etc.).

It's the same reason you'd want anything to be programmable: Automating away the tedious stuff.

> GIMP has Script Fu (and a newer Python interface) which has been used for wonderfully time-saving things (e.g. process a thousand images with the same plugins and settings and such, implement your own custom processing tools by combining existing ones, etc.)

Begin scriptable and having a CLI are two orthogonal concepts. With Script FU, GIMP itself executes scripts. If gimp had a CLI it means that you could be able to do stuff like "gimp --select-pen 2px solid black --moveTo 0 0 --lineTo 100 100 --lineTo 50 50" for instance (for which I don't see the point of using GIMP to do).

Now you are picking on minor wording choices. You asked for clarification and when it was provided you start beating up the person who responded with meaningful content.

Automated file conversion, e.g odf to pdf, comes to mind.

> Automated file conversion, e.g odf to pdf, comes to mind.

but why would it have to be related to libreoffice at all? couldn't the ODF format be implemented as a library, which then both libreoffice and "odf2pdf" command could be implemented upon ?

Once you have a library for reading ODF, reasoning about its structure, manipulating it and rendering it in various formats, that's just libreoffice without the GUI. When starting fresh it might be a decent idea to make it a library, but I don't think it's worth transitioning to if you started with a more traditional design

you could get the feature from any number of areas, I'm just saying that in a lot of cases, the GUI can act as a "gateway" to understanding the functionality of the application and the CLI can then be used to implement/extend/whatever said functionality for personal use. Handbrake is one that I think implements this well.