cflann::hierarchicalClustering with uchar data (Bug #1965)

This issue is about using uchar data as input for the cvflann::hierarchicalClustering method.

It is related to a similar topic where it was suggested to use the cvflann namespace instead of cv::flann for creating a search index of type uchar.

Following this suggestion, trying to compile the code below creates an error:

.\OpenCvTest.cpp(34) : error C2664: 'cvflann::hierarchicalClustering' : cannot convert parameter 2 from 'cvflann::Matrix<T>' to 'cvflann::Matrix<T> &'
with
[
    T=unsigned char
]
and
[
    T=cvflann::Accumulator<unsigned char>::Type
]

If I replace the uchar arrays and matrix objects with float, then the code successfully compiles and executes.

#include <opencv2/opencv.hpp>
#include <opencv2/flann/flann.hpp>

int main(int argc, char* argv[])
{
    int nRows = 100000;
    int nCols = 128;
    int nClusters = nRows / 100;

    int valueMax = 255;

    uchar* data = new uchar[nRows * nCols];

    for(int i = 0; i < nRows; i++)
    {
        for(int j = 0; j < nCols; j++)
        {
            data[i * nCols + j] = (uchar)(rand() % (valueMax + 1));
        }
    }

    cvflann::Matrix<uchar> dataMat = cvflann::Matrix<uchar>(data, nRows, nCols);

    uchar* clusters = new uchar[nClusters * nCols];
    cvflann::Matrix<uchar> clustersMat = cvflann::Matrix<uchar>(clusters, nClusters, nCols);

    cvflann::KMeansIndexParams params = cvflann::KMeansIndexParams();

    cvflann::hierarchicalClustering<cvflann::L2<uchar>>(dataMat, clustersMat, params);

    return 0;
}