Question

I am new to OpenCV and I am trying to create a n-dimensional array and access each element using CvMatND.

I can access a 2D matrix by data[i*step + j*nchannels + 0], how do I access the elements of a matrix created by

      int size[] = { 12, 12, 12 };
      CvMatND* matB = cvCreateMatND(3, size, CV_8U);
      int *Data = matA->data.i;

Thanks

Answer 1

I’ve reviewed and tested my previous answer, and as you have found out it was not accurate.

This is the working code to iterate on all the elements of a 3D array.

int size[] = { 5, 5, 5 };
CvMatND* matA = cvCreateMatND(3, size, CV_32F);
cvSetZero(matA);

for (int x = 0; x < matA->dim[0].size; x++)
{
    for (int y = 0; y < matA->dim[1].size; y++)
    {
        for (int z = 0; z < matA->dim[2].size; z++)
        {
            unsigned char* ptr = matA->data.ptr + ((size_t)x * matA->dim[0].step) + ((size_t)y * matA->dim[1].step) + ((size_t)z * matA->dim[2].step);
            float value = *(float*)ptr;

            printf("x:%d y:%d z:%d --> %f\n", x, y, z, value);
        }
    }
}