std::unique_ptr JpegCompression::compress()

in src/jpegCompression.cpp [46:94]

• 46 lines of code
• 6 McCabe index (conditional complexity)

std::unique_ptr<uint8_t[]> JpegCompression::compress(
    const boost::gil::rgb8_view_t &view, size_t *size) {
  typedef typename boost::gil::channel_type<
      typename boost::gil::rgb8_view_t::value_type>::type channel_t;
  _cinfo.image_width = (JDIMENSION)view.width();
  _cinfo.image_height = (JDIMENSION)view.height();
  _cinfo.input_components =
      boost::gil::num_channels<boost::gil::rgb8_view_t>::value;
  _cinfo.in_color_space = boost::gil::detail::jpeg_write_support<
      channel_t, typename boost::gil::color_space_type<
                     boost::gil::rgb8_view_t>::type>::_color_space;

  size_t outlen = 0;
  unsigned char *imgd = 0;
  jpeg_mem_dest(&_cinfo, &imgd, &outlen);
  jpeg_set_defaults(&_cinfo);
  jpeg_set_quality(&_cinfo, _quality, TRUE);

  if (_subsampling == subsample_444) {
    _cinfo.comp_info[0].h_samp_factor = 1;
    _cinfo.comp_info[0].v_samp_factor = 1;
  } else if (_subsampling == subsample_440) {
    _cinfo.comp_info[0].h_samp_factor = 1;
    _cinfo.comp_info[0].v_samp_factor = 2;
  } else if (_subsampling == subsample_422) {
    _cinfo.comp_info[0].h_samp_factor = 2;
    _cinfo.comp_info[0].v_samp_factor = 1;
  } else if (_subsampling == subsample_420) {
    _cinfo.comp_info[0].h_samp_factor = 2;
    _cinfo.comp_info[0].v_samp_factor = 2;
  }

  jpeg_start_compress(&_cinfo, TRUE);
  std::vector<boost::gil::pixel<
      uint8_t, boost::gil::layout<typename boost::gil::color_space_type<
                   boost::gil::rgb8_view_t>::type> > >
      row(view.width());
  JSAMPLE *row_address = reinterpret_cast<JSAMPLE *>(&row.front());
  for (int y = 0; y < view.height(); ++y) {
    std::copy(view.row_begin(y), view.row_end(y), row.begin());
    jpeg_write_scanlines(&_cinfo, (JSAMPARRAY)&row_address, 1);
  }
  jpeg_finish_compress(&_cinfo);
  std::unique_ptr<uint8_t[]> output = std::make_unique<uint8_t[]>(outlen);
  std::move(imgd, imgd + outlen, output.get());
  jpeg_destroy_compress(&_cinfo);
  *size = outlen;
  return output;
}