var files = Directory.EnumerateFiles(baseDir, "*.*", SearchOption.AllDirectories).ToArray();

const int numberOfBins = 16;
const double normalFactor = 64;

var fingerprints = new List<ImageFingerPrint>();

foreach(var file in files)
{
    var img = new Image<Gray, byte>(file);

    var hist = new DenseHistogram(numberOfBins, new RangeF(0, byte.MaxValue));
    hist.Calculate(new[] {img}, false, null);
    hist.Normalize(normalFactor);
    var data = hist.MatND.ManagedArray.Cast<float>().ToArray();

    var fingerprint = new byte[numberOfBins];
    for(int i = 0; i < numberOfBins; ++i)
    {
    fingerprint[i] = (byte)Math.Round(data[i]);
    }
    fingerprints.Add(new ImageFingerPrint { FileName = file, FingerPrint = fingerprint });
}