xmpsample.cpp

Sample usage of high-level XMP classes.

// SPDX-License-Identifier: GPL-2.0-or-later
// Sample/test for high level XMP classes. See also addmoddel.cpp
 
#include <exiv2/exiv2.hpp>
 
#include <cassert>
#include <cmath>
#include <iostream>
 
bool isEqual(float a, float b) {
  double d = std::fabs(a - b);
  return d < 0.00001;
}
 
int main() try {
  Exiv2::XmpParser::initialize();
  ::atexit(Exiv2::XmpParser::terminate);
 
  // The XMP property container
  Exiv2::XmpData xmpData;
 
  // -------------------------------------------------------------------------
  // Teaser: Setting XMP properties doesn't get much easier than this:
 
  xmpData["Xmp.dc.source"] = "xmpsample.cpp";  // a simple text value
  xmpData["Xmp.dc.subject"] = "Palmtree";      // an array item
  xmpData["Xmp.dc.subject"] = "Rubbertree";    // add a 2nd array item
  // a language alternative with two entries and without default
  xmpData["Xmp.dc.title"] = "lang=de-DE Sonnenuntergang am Strand";
  xmpData["Xmp.dc.title"] = "lang=en-US Sunset on the beach";
 
  // -------------------------------------------------------------------------
  // Any properties can be set provided the namespace is known. Values of any
  // type can be assigned to an Xmpdatum, if they have an output operator. The
  // default XMP value type for unknown properties is a simple text value.
 
  xmpData["Xmp.dc.one"] = -1;
  xmpData["Xmp.dc.two"] = 3.1415;
  xmpData["Xmp.dc.three"] = Exiv2::Rational(5, 7);
  xmpData["Xmp.dc.four"] = static_cast<uint16_t>(255);
  xmpData["Xmp.dc.five"] = 256;
  xmpData["Xmp.dc.six"] = false;
 
  // In addition, there is a dedicated assignment operator for Exiv2::Value
  Exiv2::XmpTextValue val("Seven");
  xmpData["Xmp.dc.seven"] = val;
  xmpData["Xmp.dc.eight"] = true;
 
  // Extracting values
  assert(xmpData["Xmp.dc.one"].toInt64() == -1);
  assert(xmpData["Xmp.dc.one"].value().ok());
 
  [[maybe_unused]] const Exiv2::Value& getv1 = xmpData["Xmp.dc.one"].value();
  assert(isEqual(getv1.toFloat(), -1));
  assert(getv1.ok());
  assert(getv1.toRational() == Exiv2::Rational(-1, 1));
  assert(getv1.ok());
 
  [[maybe_unused]] const Exiv2::Value& getv2 = xmpData["Xmp.dc.two"].value();
  assert(isEqual(getv2.toFloat(), 3.1415f));
  assert(getv2.ok());
  assert(getv2.toInt64() == 3);
  assert(getv2.ok());
  [[maybe_unused]] Exiv2::Rational R = getv2.toRational();
  assert(getv2.ok());
  assert(isEqual(static_cast<float>(R.first) / R.second, 3.1415f));
 
  [[maybe_unused]] const Exiv2::Value& getv3 = xmpData["Xmp.dc.three"].value();
  assert(isEqual(getv3.toFloat(), 5.0f / 7.0f));
  assert(getv3.ok());
  assert(getv3.toInt64() == 0);  // long(5.0 / 7.0)
  assert(getv3.ok());
  assert(getv3.toRational() == Exiv2::Rational(5, 7));
  assert(getv3.ok());
 
  [[maybe_unused]] const Exiv2::Value& getv6 = xmpData["Xmp.dc.six"].value();
  assert(getv6.toInt64() == 0);
  assert(getv6.ok());
  assert(getv6.toFloat() == 0.0f);
  assert(getv6.ok());
  assert(getv6.toRational() == Exiv2::Rational(0, 1));
  assert(getv6.ok());
 
  const Exiv2::Value& getv7 = xmpData["Xmp.dc.seven"].value();
  getv7.toInt64();  // this should fail
  assert(!getv7.ok());
 
  [[maybe_unused]] const Exiv2::Value& getv8 = xmpData["Xmp.dc.eight"].value();
  assert(getv8.toInt64() == 1);
  assert(getv8.ok());
  assert(getv8.toFloat() == 1.0f);
  assert(getv8.ok());
  assert(getv8.toRational() == Exiv2::Rational(1, 1));
  assert(getv8.ok());
 
  // Deleting an XMP property
  auto pos = xmpData.findKey(Exiv2::XmpKey("Xmp.dc.eight"));
  if (pos == xmpData.end())
    throw Exiv2::Error(Exiv2::ErrorCode::kerErrorMessage, "Key not found");
  xmpData.erase(pos);
 
  // -------------------------------------------------------------------------
  // Exiv2 has specialized values for simple XMP properties, arrays of simple
  // properties and language alternatives.
 
  // Add a simple XMP property in a known namespace
  auto v = Exiv2::Value::create(Exiv2::xmpText);
  v->read("image/jpeg");
  xmpData.add(Exiv2::XmpKey("Xmp.dc.format"), v.get());
 
  // Add an ordered array of text values.
  v = Exiv2::Value::create(Exiv2::xmpSeq);  // or xmpBag or xmpAlt.
  v->read("1) The first creator");          // The sequence in which the array
  v->read("2) The second creator");         // elements are added is their
  v->read("3) And another one");            // order in the array.
  xmpData.add(Exiv2::XmpKey("Xmp.dc.creator"), v.get());
 
  // Add a language alternative property
  v = Exiv2::Value::create(Exiv2::langAlt);
  v->read("lang=de-DE Hallo, Welt");  // The default doesn't need a
  v->read("Hello, World");            // qualifier
  xmpData.add(Exiv2::XmpKey("Xmp.dc.description"), v.get());
 
  // According to the XMP specification, Xmp.tiff.ImageDescription is an
  // alias for Xmp.dc.description. Exiv2 treats an alias just like any
  // other property and leaves it to the application to implement specific
  // behaviour if desired.
  xmpData["Xmp.tiff.ImageDescription"] = "TIFF image description";
  xmpData["Xmp.tiff.ImageDescription"] = "lang=de-DE TIFF Bildbeschreibung";
 
  // -------------------------------------------------------------------------
  // Register a namespace which Exiv2 doesn't know yet. This is only needed
  // when properties are added manually. If the XMP metadata is read from an
  // image, namespaces are decoded and registered at the same time.
  Exiv2::XmpProperties::registerNs("myNamespace/", "ns");
 
  // -------------------------------------------------------------------------
  // Add a property in the new custom namespace.
  xmpData["Xmp.ns.myProperty"] = "myValue";
 
  // -------------------------------------------------------------------------
  // There are no specialized values for structures, qualifiers and nested
  // types. However, these can be added by using an XmpTextValue and a path as
  // the key.
 
  // Add a structure
  Exiv2::XmpTextValue tv("16");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpDM.videoFrameSize/stDim:w"), &tv);
  tv.read("9");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpDM.videoFrameSize/stDim:h"), &tv);
  tv.read("inch");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpDM.videoFrameSize/stDim:unit"), &tv);
 
  // Add an element with a qualifier (using the namespace registered above)
  xmpData["Xmp.dc.publisher"] = "James Bond";  // creates an unordered array
  xmpData["Xmp.dc.publisher[1]/?ns:role"] = "secret agent";
 
  // Add a qualifier to an array element of Xmp.dc.creator (added above)
  tv.read("programmer");
  xmpData.add(Exiv2::XmpKey("Xmp.dc.creator[2]/?ns:role"), &tv);
 
  // Add an array of structures
  tv.read("");  // Clear the value
  tv.setXmpArrayType(Exiv2::XmpValue::xaBag);
  xmpData.add(Exiv2::XmpKey("Xmp.xmpBJ.JobRef"), &tv);  // Set the array type.
 
  tv.setXmpArrayType(Exiv2::XmpValue::xaNone);
  tv.read("Birthday party");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpBJ.JobRef[1]/stJob:name"), &tv);
  tv.read("Photographer");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpBJ.JobRef[1]/stJob:role"), &tv);
 
  tv.read("Wedding ceremony");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpBJ.JobRef[2]/stJob:name"), &tv);
  tv.read("Best man");
  xmpData.add(Exiv2::XmpKey("Xmp.xmpBJ.JobRef[2]/stJob:role"), &tv);
 
  // Add a creator contact info structure
  xmpData["Xmp.iptc.CreatorContactInfo/Iptc4xmpCore:CiAdrCity"] = "Kuala Lumpur";
  xmpData["Xmp.iptc.CreatorContactInfo/Iptc4xmpCore:CiAdrCtry"] = "Malaysia";
  xmpData["Xmp.iptc.CreatorContactInfo/Iptc4xmpCore:CiUrlWork"] = "http://www.exiv2.org";
 
  // -------------------------------------------------------------------------
  // Output XMP properties
  for (auto&& md : xmpData) {
    std::cout << std::setfill(' ') << std::left << std::setw(44) << md.key() << " " << std::setw(9) << std::setfill(' ')
              << std::left << md.typeName() << " " << std::dec << std::setw(3) << std::setfill(' ') << std::right
              << md.count() << "  " << std::dec << md.value() << std::endl;
  }
 
  // -------------------------------------------------------------------------
  // Serialize the XMP data and output the XMP packet
  std::string xmpPacket;
  if (0 != Exiv2::XmpParser::encode(xmpPacket, xmpData)) {
    throw Exiv2::Error(Exiv2::ErrorCode::kerErrorMessage, "Failed to serialize XMP data");
  }
  std::cout << xmpPacket << "\n";
 
  // Cleanup
  Exiv2::XmpParser::terminate();
 
  return EXIT_SUCCESS;
} catch (Exiv2::Error& e) {
  std::cout << "Caught Exiv2 exception '" << e << "'\n";
  return EXIT_FAILURE;
}