get IMAGE_STRUCTURE metadata

[mdsumner]

how?

  // FIXME: this is unused, how to get the compression type if present?
  // char **MDdomain = GDALGetMetadataDomainList(hDataset);
  //
  // int mdi = 0; // iterate though MetadataDomainList
  // int imgstruct_i = -1;
  // bool has_compress = false;
  // while (MDdomain && MDdomain[mdi] != NULL) {
  //   if (strcmp(MDdomain[mdi], "IMAGE_STRUCTURE") == 0) {
  //     Rprintf("it has it\n");
  //     imgstruct_i = mdi;
  //   }
  //   mdi++;
  // }
  // //cleanup
  // CSLDestroy(MDdomain);

  // char **papszMetadata = GDALGetMetadata( hDataset, "IMAGE_STRUCTURE" );
  // int imsi = 0; // iterate though IMAGE_STRUCTURE list
  // int imgstruct_i = -1;
  // bool has_compress = false;
  // while (papszMetadata && papszMetadata[imsi] != NULL) {
  //   if (strcmp(papszMetadata[imsi], "COMPRESSION") == 0) {
  //     Rprintf("it has it\n");
  //     imgstruct_i = imsi;
  //   }
  //   imsi++;
  // }
  // //cleanup
  // CSLDestroy(papszMetadata);

[mdsumner]

this can be got from the json output used in vapour_raster_info