You can start by running sudo apt install tesseract-ocr and then reading its docs.
It appears to be as simple as tesseract <infile> <outfile>. Possibly could even pipe (or tee) the screenshot straight into that and save both an image and a text file in a single command line.
So something like this should do the trick:
gnome-screenshot -f - | tee /Microsoft/yourPrivacy/$(date +%s).png | tesseract - /Microsoft/yourPrivacy/$(date +%s).txt
Skip the database, just use grep to search that directory if you need to find anything. Voilà, homemade Recall.
It is much better to search using ElasticSearch or Sphinx. Grep is super slow, non indexed and can’t do natural language full text searches. It’s pretty much useless for any real world text search you’d want from OCRed content. And all these better tools are free and open source, so really a no brainer.
I’m sure there are many ways to improve on this solution, but they would all require significantly more effort (ElasticSearch isn’t exactly trivial to set up).
This is really just a proof of concept, the most minimal viable implementation that gets you something similar in terms of functionality.
For instance, Windows Recall stores OCR content tagged by app, this solution doesn’t. Also, as others have mentioned, a practical implementation should likely check if anything has changed at all and discard any screenshots that don’t have any new data.
