The Encyclopedia of Mathematics is based on an encyclopedia that had its formulae written in TeX, which were saved as png images. On its way through the various publishers the original TeX source code was lost. Thus, the encyclopedia now contains a bunch of png images with computer generated TeX formulas. Example:
I thus want to transform all these images (about 150,000 of them) back to TeX code. I have found the Mathpix API, however they are not open source. Do you know of any open source alternatives?