Not what you're looking for, but as a point of interest Photoshop actually has accumulated several layers of internal scripting over the years. The newest and coolest is an embedded Node.js server - you can pull in arbitrary node modules and run them in a context where various PS-related APIs are exposed.
The drawbacks are:
1. Not all features have nice interfaces. For some things you need to go through this ancient, hairy API based on tons of (sparsely documented) magic strings.
2. Most of the APIs are made to support the UI, so it can be hard or easy to do things depending on how the UI works. For things involving settings dialogs, or anything that's a multistep process in the UI, it can be pretty nontrivial.
The drawbacks are:
1. Not all features have nice interfaces. For some things you need to go through this ancient, hairy API based on tons of (sparsely documented) magic strings.
2. Most of the APIs are made to support the UI, so it can be hard or easy to do things depending on how the UI works. For things involving settings dialogs, or anything that's a multistep process in the UI, it can be pretty nontrivial.