addmoddel.cpp

Sample usage of high-level metadata operations.

// ***************************************************************** -*- C++ -*-
// addmoddel.cpp
// Sample program showing how to add, modify and delete Exif metadata.

#include <exiv2/exiv2.hpp>

#include <iostream>
#include <iomanip>
#include <cassert>

int main(int argc, char* const argv[])
try {
    if (argc != 2) {
        std::cout << "Usage: " << argv[0] << " file\n";
        return 1;
    }
    std::string file(argv[1]);

    // Container for exif metadata. This is an example of creating
    // exif metadata from scratch. If you want to add, modify, delete
    // metadata that exists in an image, start with ImageFactory::open
    Exiv2::ExifData exifData;

    // *************************************************************************
    // Add to the Exif data

    // This is the quickest way to add (simple) Exif data. If a metadatum for
    // a given key already exists, its value is overwritten. Otherwise a new
    // tag is added.
    exifData["Exif.Image.Model"] = "Test 1";                     // AsciiValue
    exifData["Exif.Image.SamplesPerPixel"] = uint16_t(162);      // UShortValue
    exifData["Exif.Image.XResolution"] = -2;            // LongValue
    exifData["Exif.Image.YResolution"] = Exiv2::Rational(-2, 3); // RationalValue
    std::cout << "Added a few tags the quick way.\n";

    // Create a ASCII string value (note the use of create)
    Exiv2::Value::AutoPtr v = Exiv2::Value::create(Exiv2::asciiString);
    // Set the value to a string
    v->read("1999:12:31 23:59:59");
    // Add the value together with its key to the Exif data container
    Exiv2::ExifKey key("Exif.Photo.DateTimeOriginal");
    exifData.add(key, v.get());
    std::cout << "Added key \"" << key << "\", value \"" << *v << "\"\n";

    // Now create a more interesting value (without using the create method)
    Exiv2::URationalValue::AutoPtr rv(new Exiv2::URationalValue);
    // Set two rational components from a string
    rv->read("1/2 1/3");
    // Add more elements through the extended interface of rational value
    rv->value_.push_back(std::make_pair(2,3));
    rv->value_.push_back(std::make_pair(3,4));
    // Add the key and value pair to the Exif data
    key = Exiv2::ExifKey("Exif.Image.PrimaryChromaticities");
    exifData.add(key, rv.get());
    std::cout << "Added key \"" << key << "\", value \"" << *rv << "\"\n";

    // *************************************************************************
    // Modify Exif data

    // Since we know that the metadatum exists (or we don't mind creating a new
    // tag if it doesn't), we can simply do this:
    Exiv2::Exifdatum& tag = exifData["Exif.Photo.DateTimeOriginal"];
    std::string date = tag.toString();
    date.replace(0, 4, "2000");
    tag.setValue(date);
    std::cout << "Modified key \"" << tag.key()
              << "\", new value \"" << tag.value() << "\"\n";

    // Alternatively, we can use findKey()
    key = Exiv2::ExifKey("Exif.Image.PrimaryChromaticities");
    Exiv2::ExifData::iterator pos = exifData.findKey(key);
    if (pos == exifData.end()) throw Exiv2::Error(Exiv2::kerErrorMessage, "Key not found");
    // Get a pointer to a copy of the value
    v = pos->getValue();
    // Downcast the Value pointer to its actual type
    Exiv2::URationalValue* prv = dynamic_cast<Exiv2::URationalValue*>(v.release());
    if (prv == 0) throw Exiv2::Error(Exiv2::kerErrorMessage, "Downcast failed");
    rv = Exiv2::URationalValue::AutoPtr(prv);
    // Modify the value directly through the interface of URationalValue
    rv->value_[2] = std::make_pair(88,77);
    // Copy the modified value back to the metadatum
    pos->setValue(rv.get());
    std::cout << "Modified key \"" << key
              << "\", new value \"" << pos->value() << "\"\n";

    // *************************************************************************
    // Delete metadata from the Exif data container

    // Delete the metadatum at iterator position pos
    key = Exiv2::ExifKey("Exif.Image.PrimaryChromaticities");
    pos = exifData.findKey(key);
    if (pos == exifData.end()) throw Exiv2::Error(Exiv2::kerErrorMessage, "Key not found");
    exifData.erase(pos);
    std::cout << "Deleted key \"" << key << "\"\n";

    // *************************************************************************
    // Finally, write the remaining Exif data to the image file
    Exiv2::Image::AutoPtr image = Exiv2::ImageFactory::open(file);
    assert(image.get() != 0);

    image->setExifData(exifData);
    image->writeMetadata();

    return 0;
}
catch (Exiv2::AnyError& e) {
    std::cout << "Caught Exiv2 exception '" << e << "'\n";
    return -1;
}