message: Properly save .pnm images through image interface
diff: @@ -81,7 +81,7 @@ static image_type get_type(std::string const& filename)
  // PNM
  - static const std::string pnm_extensions[] = { ".pbm", ".pgm", ".ppm", ".PBM", ".PGM", ".PPM" };
  + static const std::string pnm_extensions[] = { ".pbm", ".pgm", ".pnm", ".ppm", ".PBM", ".PGM", ".PNM", ".PPM" };
  if (std::find(pnm_extensions, pnm_extensions + 6, p.extension()) != pnm_extensions + 6)
  {
  @@ -275,7 +275,7 @@ bool image::save(std::string const& filename, file_base::save_options const& opt
  {
  case PNM:
  {
  - pnm_image pnm;
  + pnm_image pnm(width(), height(), format(), data());
  return pnm.save(fn, options);
  }
  