exifcomment.cpp

// SPDX-License-Identifier: GPL-2.0-or-later
// Abstract : Sample program showing how to set the Exif comment of an image, Exif.Photo.UserComment

#include <exiv2/exiv2.hpp>
#include <iostream>

// *****************************************************************************
// Main
int main(int argc, char* const argv[]) {
  try {
    Exiv2::XmpParser::initialize();
    ::atexit(Exiv2::XmpParser::terminate);

    if (argc != 2) {
      std::cout << "Usage: " << argv[0] << " file\n";
      return EXIT_FAILURE;
    }

    auto image = Exiv2::ImageFactory::open(argv[1]);
    image->readMetadata();
    Exiv2::ExifData& exifData = image->exifData();

    /*
      Exiv2 uses a CommentValue for Exif user comments. The format of the
      comment string includes an optional charset specification at the beginning:

      [charset=[Ascii|Jis|Unicode|Undefined]] comment

      Undefined is used as a default if the comment doesn't start with a charset
      definition.

      Following are a few examples of valid comments. The last one is written to
      the file.
     */
    exifData["Exif.Photo.UserComment"] = "charset=Unicode A Unicode Exif comment added with Exiv2";
    exifData["Exif.Photo.UserComment"] = "charset=Undefined An undefined Exif comment added with Exiv2";
    exifData["Exif.Photo.UserComment"] = "Another undefined Exif comment added with Exiv2";
    exifData["Exif.Photo.UserComment"] = "charset=Ascii An ASCII Exif comment added with Exiv2";

    std::cout << "Writing user comment '" << exifData["Exif.Photo.UserComment"] << "' back to the image\n";

    image->writeMetadata();

    return EXIT_SUCCESS;
  } catch (Exiv2::Error& e) {
    std::cout << "Caught Exiv2 exception '" << e << "'\n";
    return EXIT_FAILURE;
  }
}