//   2D MEDIAN FILTER wrapper
//     image  - input image
//     result - output image
//     N      - width of the image
//     M      - height of the image
void medianfilter(element *image, element *result, int N, int M)
{
    //   Check arguments
    if (!image || N < 1 || M < 1)
        return;
    //   Allocate memory for signal extension
    element *extension = new element[(N + 2) * (M + 2)];
    //   Check memory allocation
    if (!extension)
        return;
    //   Create image extension
    for (int i = 0; i < M; ++i)
    {
        memcpy(extension + (N + 2) * (i + 1) + 1, image + N * i, N * sizeof(element));
        extension[(N + 2) * (i + 1)] = image[N * i];
        extension[(N + 2) * (i + 2) - 1] = image[N * (i + 1) - 1];
    }
    //   Fill first line of image extension
    memcpy(extension, extension + N + 2, (N + 2) * sizeof(element));
    //   Fill last line of image extension
    memcpy(extension + (N + 2) * (M + 1), extension + (N + 2) * M, (N + 2) * sizeof(element));
    //   Call median filter implementation
    _medianfilter(extension, result ? result : image, N + 2, M + 2);
    //   Free memory
    delete[] extension;
}