where does zxing check for Luminance, finder pattern and error correction level

Question

Anyone knows where does zxing library (in Java) check for Luminance and other factors that would affect the readability of a QR code?
For example, if the luminance is lower than some number, it will show a massage saying "Luminance is low". Where exactly is this number checked in the zxing library? And also where are the other factors that have been checked for scannability?
I have looked into LuminanceSource and Detector libraries, but didn't found that specific number or function checking for these.
Also what are the all factors that I need to check to make sure the QR code is scannable?

Answer 1

Did you look at the source? It's pretty clear. LuminanceSource is not the place; look at HybridBinarizer for luminance. There is no such thing as a "check for scannability". qrcode.Detector calls FinderPatternFinder to locate finder patterns. I don't know what you mean by error correction level but the common.reedsolomon package performs correction, as you can probably guess just by the name.