Recover Steganography Code embedded in RGB Values. e is the bit position.

steganographer.cpp

auto steganographer(vector<vector<long long>> r, int e) {
    bool f[r.size() * r[0].size()],*t;
    int z = 0;
    for (i:r)
        for (j:i)
            for(l:{3,2,1,0})
                if (e&(1<<l)) f[z++] = j >> 8*l & 1;
    string s;
    for (t = f; t < f + z; t += 7)
        s += accumulate(t, t + 7, 0, [](int x, int y) { return (x << 1) + y; });
    return s;
}