# addmoddel.cpp

Sample usage of high-level metadata operations.

    // ***************************************************************** -*- C++ -*-
    // addmoddel.cpp, $Rev: 560 $
    // Sample program showing how to add, modify and delete Exif metadata.

    #include "image.hpp"
    #include "exif.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"] = int32_t(-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 \"" << 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(1, "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(1, "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(1, "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;
    }