According to tokei, the lib/ directory from the reference implementation [0] has 93821 lines of C++ code and 22164 lines of "C Header" (which seems to be a mix of C++ headers, C headers, and headers that are compatible with both C and C++). The tools/ directory adds 16314 lines of C++ code and 1952 lines of "C Header".
So at least if GP was talking about libjxl "100K+" would be more accurate.
So at least if GP was talking about libjxl "100K+" would be more accurate.
[0]: https://github.com/libjxl/libjxl