static void do_body (uint8_t *input, uint8_t *red, uint8_t *blue,
                        uint8_t *green, GstBayer2RGB *filter) {
  int ip, op;   /* input and output pointers */
  int w, h;     /* loop indices */
  int type;     /* calculated colour of current element */
  int a1, a2;
  int v1, v2, h1, h2;

  /*
   * We are processing row (line) by row, starting with the second
   * row and continuing through the next to last.  Each row is processed
   * column by column, starting with the second and continuing through
   * to the next to last.
   */
  for (h = 1; h < filter->height - 1; h++) {
    /*
     * Remember we are processing "row by row". For each row, we need
     * to set the type of the first element to be processed.  Since we
     * have already processed the edges, the "first element" will be
     * the pixel at position (1,1).  Assuming RG format, this should
     * be BLUE for odd-numbered rows and GREENR for even rows.
     */
    if (h & 1)
      type = RED;
    else
      type = GREENB;
    /* Calculate the starting position for the row */
    op = h * filter->width;     /* output (converted) pos */
    ip = h * filter->stride;    /* input (bayer data) pos */
    for (w = 1; w < filter->width - 1; w++) {
      op++;     /* we are processing "horizontally" */
      ip++;
      switch (type) {
        case RED:
          red[op] = input[ip];
          blue[op] = (input[ip - filter->stride - 1] +
                   input[ip - filter->stride + 1] +
                   input[ip + filter->stride - 1] +
                   input[ip + filter->stride + 1] + 2) / 4;
          v1 = input[ip + filter->stride];
          v2 = input[ip - filter->stride];
          h1 = input[ip + 1];
          h2 = input[ip - 1];
          a1 = abs (v1 - v2);
          a2 = abs (h1 - h2);
          if (a1 < a2)
            green[op] = (v1 + v2 + 1) / 2;
          else if (a1 > a2)
            green[op] = (h1 + h2 + 1) / 2;
          else
            green[op] = (v1 + h1 + v2 + h2 + 2) / 4;
          type = GREENR;                /* step horizontally */
          break;
        case GREENR:
          red[op] = (input[ip + 1] + input[ip - 1] + 1) / 2;
          green[op] = input[ip];
          blue[op] = (input[ip - filter->stride] +
                   input[ip + filter->stride] + 1) / 2;
          type = RED;
          break;
        case GREENB:
          red[op] = (input[ip - filter->stride] +
                   input[ip + filter->stride] + 1) / 2;
          green[op] = input[ip];
          blue[op] = (input[ip + 1] + input[ip - 1] + 1) / 2;
          type = BLUE;
          break;

        case BLUE:
          red[op] = (input[ip - filter->stride - 1] +
                   input[ip - filter->stride + 1] +
                   input[ip + filter->stride - 1] +
                   input[ip + filter->stride + 1] + 2) / 4;
          blue[op] = input[ip];
          v1 = input[ip + filter->stride];
          v2 = input[ip - filter->stride];
          h1 = input[ip + 1];
          h2 = input[ip - 1];
          a1 = abs (v1 - v2);
          a2 = abs (h1 - h2);
          if (a1 < a2)
            green[op] = (v1 + v2 + 1) / 2;
          else if (a1 > a2)
            green[op] = (h1 + h2 + 1) / 2;
          else
            green[op] = (v1 + h1 + v2 + h2 + 2) / 4;
          type = GREENB;
          break;
      }
    }
  }
}