You could have a look at the ISO spec on QR Codes to get the authoritative source on what kind of processing required.
Alternatively (and what I would recommend), is grab a library that is dedicated to QR Code reading (I‘ve used Quirc, for example) and just read the code.
Typically you threshold an image to get a binary representation (1: black, 0: white). Then you detect the finder patterns by looking for 1-1-3-1-1 runs of black/white. Once you have a bunch of finder patterns localized, you form triplets and decode the binary matrix that they span.
Comments
You could have a look at the ISO spec on QR Codes to get the authoritative source on what kind of processing required.
Alternatively (and what I would recommend), is grab a library that is dedicated to QR Code reading (I‘ve used Quirc, for example) and just read the code.
Typically you threshold an image to get a binary representation (1: black, 0: white). Then you detect the finder patterns by looking for 1-1-3-1-1 runs of black/white. Once you have a bunch of finder patterns localized, you form triplets and decode the binary matrix that they span.