Function SaveEXRNPartImageToMemory

third-party/tinyexr/tinyexr.h:7603–7981

can save a single or multi-part image (no deep* formats)

// can save a single or multi-part image (no deep* formats)
static size_t SaveEXRNPartImageToMemory(const EXRImage* exr_images,
                                        const EXRHeader** exr_headers,
                                        unsigned int num_parts,
                                        unsigned char** memory_out, const char** err) {
  if (exr_images == NULL || exr_headers == NULL || num_parts == 0 ||
      memory_out == NULL) {
    SetErrorMessage("Invalid argument for SaveEXRNPartImageToMemory",
                    err);
    return 0;
  }
  {
    for (unsigned int i = 0; i < num_parts; ++i) {
      if (exr_headers[i]->compression_type < 0) {
        SetErrorMessage("Invalid argument for SaveEXRNPartImageToMemory",
                        err);
        return 0;
      }
#if !TINYEXR_USE_PIZ
      if (exr_headers[i]->compression_type == TINYEXR_COMPRESSIONTYPE_PIZ) {
        SetErrorMessage("PIZ compression is not supported in this build",
                        err);
        return 0;
      }
#endif
      if (exr_headers[i]->compression_type == TINYEXR_COMPRESSIONTYPE_ZFP) {
#if !TINYEXR_USE_ZFP
        SetErrorMessage("ZFP compression is not supported in this build",
                        err);
        return 0;
#else
        // All channels must be fp32.
        // No fp16 support in ZFP atm(as of 2023 June)
        // https://github.com/LLNL/fpzip/issues/2
        for (int c = 0; c < exr_headers[i]->num_channels; ++c) {
          if (exr_headers[i]->requested_pixel_types[c] != TINYEXR_PIXELTYPE_FLOAT) {
            SetErrorMessage("Pixel type must be FLOAT for ZFP compression",
                            err);
            return 0;
          }
        }
#endif
      }
    }
  }

  std::vector<unsigned char> memory;

  // Header
  {
    const char header[] = { 0x76, 0x2f, 0x31, 0x01 };
    memory.insert(memory.end(), header, header + 4);
  }

  // Version
  // using value from the first header
  int long_name = exr_headers[0]->long_name;
  {
    char marker[] = { 2, 0, 0, 0 };