struct pixel *pointers = malloc(sizeof(struct pixel) * m);
        for (int i = 0; i < m; i++){
                pointers[i] = pointer[0] + i * sizeof(struct pixel);
        }
First, allocate space for m `struct pixel *` values, where m is the 
 *    height of the image.  Each pointer will eventually point to one row of 
 *    pixel data.
 * 2. For each pointer you just allocated, initialize it to point to 
 *    heap-allocated space for an entire row of pixel data.
