I'm trying to extract text from a scanned technical drawing. For confidentiality reasons, I cannot post the actual drawing, but it looks similar to this, but a lot busier with more text within shapes. The problem is quite complex due to issues with letters touching both each other and it's surrounding borders / symbols.
I found an interesting paper that does exactly this called "Detection of Text Regions From Digital Engineering Drawings" by Zhaoyang Lu. It's behind a paywall so you might not be able to access it, but essentially it tries to erase everything that's not text from the image through mainly two steps:
1) Erases linear components, including long and short isolated lines
2) Erases non-text strokes in terms of analysis of connected components of strokes
What kind of OpenCV functions would help in performing these operations? I would rather not write something from the ground up to do these, but I suspect I might have to.
I've tried using a template-based approach to try to isolate the text, but since the text location isn't completely normalized between drawings (even in the same project), it fails in detecting text past the first scanned figure.