func: static void read_sgi_header(ByteIOContext *f, SGIInfo *info)
  {
      info->magic = (unsigned short) get_be16(f);
      info->rle = get_byte(f);
      info->bytes_per_channel = get_byte(f);
      info->dimension = (unsigned short)get_be16(f);
      info->xsize = (unsigned short) get_be16(f);
      info->ysize = (unsigned short) get_be16(f);
      info->zsize = (unsigned short) get_be16(f);
  #ifdef DEBUG
      printf("sgi header fields:\n");
      printf("  magic: %d\n", info->magic);
      printf("    rle: %d\n", info->rle);
      printf("    bpc: %d\n", info->bytes_per_channel);
      printf("    dim: %d\n", info->dimension);
      printf("  xsize: %d\n", info->xsize);
      printf("  ysize: %d\n", info->ysize);
      printf("  zsize: %d\n", info->zsize);
  #endif
      return;
  }