  GLint ComputeImageDataSize(GLint width, GLint height) const {
    GLint row_size = width * bytes_per_pixel_;
    if (height > 1) {
      GLint temp = row_size + pack_alignment_;
      GLint padded_row_size = (temp / pack_alignment_) * pack_alignment_;
      GLint size_of_all_but_last_row = (height - 1) * padded_row_size;
      return size_of_all_but_last_row + row_size;
    } else {
      return height * row_size;
    }
  }

Unknown