exiv2/src/exif.cpp

// ***************************************************************** -*- C++ -*-
/*
 * Copyright (C) 2004-2021 Exiv2 authors
 * This program is part of the Exiv2 distribution.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, 5th Floor, Boston, MA 02110-1301 USA.
 */
/*
  File:      exif.cpp
  Author(s): Andreas Huggel (ahu) <ahuggel@gmx.net>
  History:   26-Jan-04, ahu: created
             11-Feb-04, ahu: isolated as a component
 */
// *****************************************************************************
// included header files
#include "config.h"

#include "exif.hpp"
#include "metadatum.hpp"
#include "tags.hpp"
#include "tags_int.hpp"
#include "value.hpp"
#include "types.hpp"
#include "error.hpp"
#include "basicio.hpp"
#include "tiffimage.hpp"
#include "tiffimage_int.hpp"
#include "tiffcomposite_int.hpp" // for Tag::root

// + standard includes
#include <iostream>
#include <sstream>
#include <utility>
#include <algorithm>
#include <cstring>
#include <cassert>
#include <cstdio>

// *****************************************************************************
namespace {

    //! Unary predicate that matches a Exifdatum with a given key
    class FindExifdatumByKey {
    public:
        //! Constructor, initializes the object with the key to look for
        explicit FindExifdatumByKey(const std::string& key) : key_(key)
        {
        }
        /*!
          @brief Returns true if the key of \em exifdatum is equal
                 to that of the object.
        */
        bool operator()(const Exiv2::Exifdatum& exifdatum) const
        {
            return key_ == exifdatum.key();
        }

    private:
        const std::string& key_;

    }; // class FindExifdatumByKey

    /*!
      @brief Exif %Thumbnail image. This abstract base class provides the
             interface for the thumbnail image that is optionally embedded in
             the Exif data. This class is used internally by ExifData, it is
             probably not useful for a client as a standalone class.  Instead,
             use an instance of ExifData to access the Exif thumbnail image.
     */
    class Thumbnail {
    public:
        //! Shortcut for a %Thumbnail auto pointer.
        using UniquePtr = std::unique_ptr<Thumbnail>;

        //! @name Creators
        //@{
        //! Virtual destructor
        virtual ~Thumbnail() = default;
        //@}

        //! Factory function to create a thumbnail for the Exif metadata provided.
        static UniquePtr create(const Exiv2::ExifData& exifData);

        //! @name Accessors
        //@{
        /*!
          @brief Return the thumbnail image in a %DataBuf. The caller owns the
                 data buffer and %DataBuf ensures that it will be deleted.
         */
        virtual Exiv2::DataBuf copy(const Exiv2::ExifData& exifData) const =0;
        /*!
          @brief Return the MIME type of the thumbnail ("image/tiff" or
                 "image/jpeg").
         */
        virtual const char* mimeType() const =0;
        /*!
          @brief Return the file extension for the format of the thumbnail
                 (".tif", ".jpg").
         */
        virtual const char* extension() const =0;
        //@}

    }; // class Thumbnail

    //! Exif thumbnail image in TIFF format
    class TiffThumbnail : public Thumbnail {
    public:
        //! Shortcut for a %TiffThumbnail auto pointer.
        using UniquePtr = std::unique_ptr<TiffThumbnail>;

        //! @name Manipulators
        //@{
        //! Assignment operator.
        TiffThumbnail& operator=(const TiffThumbnail& rhs);
        //@}

        //! @name Accessors
        //@{
        Exiv2::DataBuf copy(const Exiv2::ExifData& exifData) const override;
        const char* mimeType() const override;
        const char* extension() const override;
        //@}

    }; // class TiffThumbnail

    //! Exif thumbnail image in JPEG format
    class JpegThumbnail : public Thumbnail {
    public:
        //! Shortcut for a %JpegThumbnail auto pointer.
        using UniquePtr = std::unique_ptr<JpegThumbnail>;

        //! @name Manipulators
        //@{
        //! Assignment operator.
        JpegThumbnail& operator=(const JpegThumbnail& rhs);
        //@}

        //! @name Accessors
        //@{
        Exiv2::DataBuf copy(const Exiv2::ExifData& exifData) const override;
        const char* mimeType() const override;
        const char* extension() const override;
        //@}

    }; // class JpegThumbnail

    //! Helper function to sum all components of the value of a metadatum
    int64_t sumToLong(const Exiv2::Exifdatum& md);

    //! Helper function to delete all tags of a specific IFD from the metadata.
    void eraseIfd(Exiv2::ExifData& ed, Exiv2::Internal::IfdId ifdId);

}  // namespace

// *****************************************************************************
// class member definitions
namespace Exiv2 {

    using namespace Internal;

    /*!
      @brief Set the value of \em exifDatum to \em value. If the object already
             has a value, it is replaced. Otherwise a new ValueType\<T\> value
             is created and set to \em value.

      This is a helper function, called from Exifdatum members. It is meant to
      be used with T = (u)int16_t, (u)int32_t or (U)Rational. Do not use directly.
    */
    template<typename T>
    Exiv2::Exifdatum& setValue(Exiv2::Exifdatum& exifDatum, const T& value)
    {
        auto v = std::make_unique<Exiv2::ValueType<T>>();
        v->value_.push_back(value);
        exifDatum.value_ = std::move(v);
        return exifDatum;
    }

    Exifdatum::Exifdatum(const ExifKey& key, const Value* pValue)
        : key_(key.clone())
    {
        if (pValue) value_ = pValue->clone();
    }

    Exifdatum::Exifdatum(const Exifdatum& rhs)
        : Metadatum(rhs)
    {
        if (rhs.key_.get() != nullptr)
            key_ = rhs.key_->clone();  // deep copy
        if (rhs.value_.get() != nullptr)
            value_ = rhs.value_->clone();  // deep copy
    }

    std::ostream& Exifdatum::write(std::ostream& os, const ExifData* pMetadata) const
    {
        if (value().count() == 0) return os;

        PrintFct       fct = printValue;
        const TagInfo* ti  = Internal::tagInfo(tag(), static_cast<IfdId>(ifdId()));
        // be careful with comments (User.Photo.UserComment, GPSAreaInfo etc).
        if ( ti ) {
            fct = ti->printFct_;
            if ( ti->typeId_ == comment ) {
              os << value().toString();
              fct = nullptr;
            }
        }
        if ( fct ) {
          // https://github.com/Exiv2/exiv2/issues/1706
          // Sometimes the type of the value doesn't match what the
          // print function expects. (The expected types are stored
          // in the TagInfo tables, but they are not enforced when the
          // metadata is parsed.) These type mismatches can sometimes
          // cause a std::out_of_range exception to be thrown.
          try {
            fct(os, value(), pMetadata);
          } catch (std::out_of_range&) {
            os << "Bad value";
#ifdef EXIV2_DEBUG_MESSAGES
            std::cerr << "Caught std::out_of_range exception in Exifdatum::write().\n";
#endif
          }
        }
        return os;
    }

    const Value& Exifdatum::value() const
    {
        if (value_.get() == nullptr)
            throw Error(kerValueNotSet);
        return *value_;
    }

    Exifdatum& Exifdatum::operator=(const Exifdatum& rhs)
    {
        if (this == &rhs) return *this;
        Metadatum::operator=(rhs);

        key_.reset();
        if (rhs.key_.get() != nullptr)
            key_ = rhs.key_->clone();  // deep copy

        value_.reset();
        if (rhs.value_.get() != nullptr)
            value_ = rhs.value_->clone();  // deep copy

        return *this;
    } // Exifdatum::operator=

    Exifdatum& Exifdatum::operator=(const std::string& value)
    {
        setValue(value);
        return *this;
    }

    Exifdatum& Exifdatum::operator=(const uint16_t& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const uint32_t& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const URational& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const int16_t& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const int32_t& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const Rational& value)
    {
        return Exiv2::setValue(*this, value);
    }

    Exifdatum& Exifdatum::operator=(const Value& value)
    {
        setValue(&value);
        return *this;
    }

    void Exifdatum::setValue(const Value* pValue)
    {
        value_.reset();
        if (pValue) value_ = pValue->clone();
    }

    int Exifdatum::setValue(const std::string& value)
    {
        if (value_.get() == nullptr) {
            TypeId type = key_->defaultTypeId();
            value_ = Value::create(type);
        }
        return value_->read(value);
    }

    int Exifdatum::setDataArea(const byte* buf, size_t len)
    {
        return value_.get() == nullptr ? -1 : value_->setDataArea(buf, len);
    }

    std::string Exifdatum::key() const
    {
        return key_.get() == nullptr ? "" : key_->key();
    }

    const char* Exifdatum::familyName() const
    {
        return key_.get() == nullptr ? "" : key_->familyName();
    }

    std::string Exifdatum::groupName() const
    {
        return key_.get() == nullptr ? "" : key_->groupName();
    }

    std::string Exifdatum::tagName() const
    {
        return key_.get() == nullptr ? "" : key_->tagName();
    }

    std::string Exifdatum::tagLabel() const
    {
        return key_.get() == nullptr ? "" : key_->tagLabel();
    }

    uint16_t Exifdatum::tag() const
    {
        return key_.get() == nullptr ? 0xffff : key_->tag();
    }

    int Exifdatum::ifdId() const
    {
        return key_.get() == nullptr ? ifdIdNotSet : key_->ifdId();
    }

    const char* Exifdatum::ifdName() const
    {
        return key_.get() == nullptr ? "" : Internal::ifdName(static_cast<Internal::IfdId>(key_->ifdId()));
    }

    int Exifdatum::idx() const
    {
        return key_.get() == nullptr ? 0 : key_->idx();
    }

    long Exifdatum::copy(byte* buf, ByteOrder byteOrder) const
    {
        return value_.get() == nullptr ? 0 : value_->copy(buf, byteOrder);
    }

    TypeId Exifdatum::typeId() const
    {
        return value_.get() == nullptr ? invalidTypeId : value_->typeId();
    }

    const char* Exifdatum::typeName() const
    {
        return TypeInfo::typeName(typeId());
    }

    long Exifdatum::typeSize() const
    {
        return static_cast<long>(TypeInfo::typeSize(typeId()));
    }

    size_t Exifdatum::count() const
    {
        return value_.get() == nullptr ? 0 : value_->count();
    }

    long Exifdatum::size() const
    {
        return value_.get() == nullptr ? 0 : static_cast<long>(value_->size());
    }

    std::string Exifdatum::toString() const
    {
        return value_.get() == nullptr ? "" : value_->toString();
    }

    std::string Exifdatum::toString(long n) const
    {
        return value_.get() == nullptr ? "" : value_->toString(n);
    }

    int64_t Exifdatum::toInt64(long n) const
    {
        return value_.get() == nullptr ? -1 : value_->toInt64(n);
    }

    float Exifdatum::toFloat(long n) const
    {
        return value_.get() == nullptr ? -1 : value_->toFloat(n);
    }

    Rational Exifdatum::toRational(long n) const
    {
        return value_.get() == nullptr ? Rational(-1, 1) : value_->toRational(n);
    }

    Value::UniquePtr Exifdatum::getValue() const
    {
        return value_.get() == nullptr ? nullptr : value_->clone();
    }

    size_t Exifdatum::sizeDataArea() const
    {
        return value_.get() == nullptr ? 0 : value_->sizeDataArea();
    }

    DataBuf Exifdatum::dataArea() const
    {
        return value_.get() == nullptr ? DataBuf(nullptr, 0) : value_->dataArea();
    }

    ExifThumbC::ExifThumbC(const ExifData& exifData)
        : exifData_(exifData)
    {
    }

    DataBuf ExifThumbC::copy() const
    {
        auto thumbnail = Thumbnail::create(exifData_);
        if (!thumbnail)
            return DataBuf();
        return thumbnail->copy(exifData_);
    }

    size_t ExifThumbC::writeFile(const std::string& path) const
    {
        auto thumbnail = Thumbnail::create(exifData_);
        if (!thumbnail.get())
            return 0;

        std::string name = path + thumbnail->extension();
        DataBuf buf(thumbnail->copy(exifData_));
        if (buf.empty())
            return 0;

        return Exiv2::writeFile(buf, name);
    }

    const char* ExifThumbC::mimeType() const
    {
        auto thumbnail = Thumbnail::create(exifData_);
        if (!thumbnail.get())
            return "";
        return thumbnail->mimeType();
    }

    const char* ExifThumbC::extension() const
    {
        auto thumbnail = Thumbnail::create(exifData_);
        if (!thumbnail)
            return "";
        return thumbnail->extension();
    }

    ExifThumb::ExifThumb(ExifData& exifData)
        : ExifThumbC(exifData), exifData_(exifData)
    {
    }

    void ExifThumb::setJpegThumbnail(const std::string& path, URational xres, URational yres, uint16_t unit)
    {
        DataBuf thumb = readFile(path); // may throw
        setJpegThumbnail(thumb.c_data(), thumb.size(), xres, yres, unit);
    }

    void ExifThumb::setJpegThumbnail(const byte* buf, size_t size, URational xres, URational yres, uint16_t unit)
    {
        setJpegThumbnail(buf, size);
        exifData_["Exif.Thumbnail.XResolution"] = xres;
        exifData_["Exif.Thumbnail.YResolution"] = yres;
        exifData_["Exif.Thumbnail.ResolutionUnit"] = unit;
    }

    void ExifThumb::setJpegThumbnail(const std::string& path)
    {
        DataBuf thumb = readFile(path); // may throw
        setJpegThumbnail(thumb.c_data(), thumb.size());
    }

    void ExifThumb::setJpegThumbnail(const byte* buf, size_t size)
    {
        exifData_["Exif.Thumbnail.Compression"] = uint16_t(6);
        Exifdatum& format = exifData_["Exif.Thumbnail.JPEGInterchangeFormat"];
        format = uint32_t(0);
        format.setDataArea(buf, size);
        exifData_["Exif.Thumbnail.JPEGInterchangeFormatLength"] = uint32_t(size);
    }

    void ExifThumb::erase()
    {
        eraseIfd(exifData_, ifd1Id);
    }

    Exifdatum& ExifData::operator[](const std::string& key)
    {
        ExifKey exifKey(key);
        auto pos = findKey(exifKey);
        if (pos == end()) {
            exifMetadata_.emplace_back(exifKey);
            return exifMetadata_.back();
        }
        return *pos;
    }

    void ExifData::add(const ExifKey& key, const Value* pValue)
    {
        add(Exifdatum(key, pValue));
    }

    void ExifData::add(const Exifdatum& exifdatum)
    {
        // allow duplicates
        exifMetadata_.push_back(exifdatum);
    }

    ExifData::const_iterator ExifData::findKey(const ExifKey& key) const
    {
        return std::find_if(exifMetadata_.begin(), exifMetadata_.end(),
                            FindExifdatumByKey(key.key()));
    }

    ExifData::iterator ExifData::findKey(const ExifKey& key)
    {
        return std::find_if(exifMetadata_.begin(), exifMetadata_.end(),
                            FindExifdatumByKey(key.key()));
    }

    void ExifData::clear()
    {
        exifMetadata_.clear();
    }

    void ExifData::sortByKey()
    {
        exifMetadata_.sort(cmpMetadataByKey);
    }

    void ExifData::sortByTag()
    {
        exifMetadata_.sort(cmpMetadataByTag);
    }

    ExifData::iterator ExifData::erase(ExifData::iterator beg, ExifData::iterator end)
    {
        return exifMetadata_.erase(beg, end);
    }

    ExifData::iterator ExifData::erase(ExifData::iterator pos)
    {
        return exifMetadata_.erase(pos);
    }

    ByteOrder ExifParser::decode(ExifData& exifData, const byte* pData, size_t size)
    {
        IptcData iptcData;
        XmpData  xmpData;
        ByteOrder bo = TiffParser::decode(exifData, iptcData, xmpData, pData, size);
#ifndef SUPPRESS_WARNINGS
        if (!iptcData.empty()) {
            EXV_WARNING << "Ignoring IPTC information encoded in the Exif data.\n";
        }
        if (!xmpData.empty()) {
            EXV_WARNING << "Ignoring XMP information encoded in the Exif data.\n";
        }
#endif
        return bo;
    }

    //! @cond IGNORE
    enum Ptt { pttLen, pttTag, pttIfd };
    struct PreviewTags {
        Ptt ptt_;
        const char* key_;
    };
    //! @endcond

    WriteMethod ExifParser::encode(Blob& blob, const byte* pData, size_t size, ByteOrder byteOrder,
                                   const ExifData& exifData)
    {
        ExifData ed = exifData;

        // Delete IFD0 tags that are "not recorded" in compressed images
        // Reference: Exif 2.2 specs, 4.6.8 Tag Support Levels, section A
        static const char* filteredIfd0Tags[] = {
            "Exif.Image.PhotometricInterpretation",
            "Exif.Image.StripOffsets",
            "Exif.Image.RowsPerStrip",
            "Exif.Image.StripByteCounts",
            "Exif.Image.JPEGInterchangeFormat",
            "Exif.Image.JPEGInterchangeFormatLength",
            "Exif.Image.SubIFDs",
            // Issue 981.  Never allow manufactured data to be written
            "Exif.Canon.AFInfoSize",
            "Exif.Canon.AFAreaMode",
            "Exif.Canon.AFNumPoints",
            "Exif.Canon.AFValidPoints",
            "Exif.Canon.AFCanonImageWidth",
            "Exif.Canon.AFCanonImageHeight",
            "Exif.Canon.AFImageWidth",
            "Exif.Canon.AFImageHeight",
            "Exif.Canon.AFAreaWidths",
            "Exif.Canon.AFAreaHeights",
            "Exif.Canon.AFXPositions",
            "Exif.Canon.AFYPositions",
            "Exif.Canon.AFPointsInFocus",
            "Exif.Canon.AFPointsSelected",
            "Exif.Canon.AFPointsUnusable",
            "Exif.Canon.AFFineRotation",
        };
        for (auto&& filteredIfd0Tag : filteredIfd0Tags) {
            auto pos = ed.findKey(ExifKey(filteredIfd0Tag));
            if (pos != ed.end()) {
#ifdef EXIV2_DEBUG_MESSAGES
                std::cerr << "Warning: Exif tag " << pos->key() << " not encoded\n";
#endif
                ed.erase(pos);
            }
        }

        // Delete IFDs which do not occur in JPEGs
        static const IfdId filteredIfds[] = {
            subImage1Id,
            subImage2Id,
            subImage3Id,
            subImage4Id,
            subImage5Id,
            subImage6Id,
            subImage7Id,
            subImage8Id,
            subImage9Id,
            subThumb1Id,
            panaRawId,
            ifd2Id,
            ifd3Id
        };
        for (auto&& filteredIfd : filteredIfds) {
#ifdef EXIV2_DEBUG_MESSAGES
            std::cerr << "Warning: Exif IFD " << filteredIfds << " not encoded\n";
#endif
            eraseIfd(ed, filteredIfd);
        }

        // IPTC and XMP are stored elsewhere, not in the Exif APP1 segment.
        IptcData emptyIptc;
        XmpData  emptyXmp;

        // Encode and check if the result fits into a JPEG Exif APP1 segment
        MemIo mio1;
        TiffHeader header(byteOrder, 0x00000008, false);
        WriteMethod wm = TiffParserWorker::encode(mio1, pData, static_cast<uint32_t>(size), ed, emptyIptc, emptyXmp,
                                                  Tag::root, TiffMapping::findEncoder, &header, nullptr);
        if (mio1.size() <= 65527) {
            append(blob, mio1.mmap(), static_cast<uint32_t>(mio1.size()));
            return wm;
        }

        // If it doesn't fit, remove additional tags

        // Delete preview tags if the preview is larger than 32kB.
        // Todo: Enhance preview classes to be able to write and delete previews and use that instead.
        // Table must be sorted by preview, the first tag in each group is the size
        static const PreviewTags filteredPvTags[] = {
            { pttLen, "Exif.Minolta.ThumbnailLength"                  },
            { pttTag, "Exif.Minolta.ThumbnailOffset"                  },
            { pttLen, "Exif.Minolta.Thumbnail"                        },
            { pttLen, "Exif.NikonPreview.JPEGInterchangeFormatLength" },
            { pttIfd, "NikonPreview"                                  },
            { pttLen, "Exif.Olympus.ThumbnailLength"                  },
            { pttTag, "Exif.Olympus.ThumbnailOffset"                  },
            { pttLen, "Exif.Olympus.ThumbnailImage"                   },
            { pttLen, "Exif.Olympus.Thumbnail"                        },
            { pttLen, "Exif.Olympus2.ThumbnailLength"                 },
            { pttTag, "Exif.Olympus2.ThumbnailOffset"                 },
            { pttLen, "Exif.Olympus2.ThumbnailImage"                  },
            { pttLen, "Exif.Olympus2.Thumbnail"                       },
            { pttLen, "Exif.OlympusCs.PreviewImageLength"             },
            { pttTag, "Exif.OlympusCs.PreviewImageStart"              },
            { pttTag, "Exif.OlympusCs.PreviewImageValid"              },
            { pttLen, "Exif.Pentax.PreviewLength"                     },
            { pttTag, "Exif.Pentax.PreviewOffset"                     },
            { pttTag, "Exif.Pentax.PreviewResolution"                 },
            { pttLen, "Exif.PentaxDng.PreviewLength"                  },
            { pttTag, "Exif.PentaxDng.PreviewOffset"                  },
            { pttTag, "Exif.PentaxDng.PreviewResolution"              },
            { pttLen, "Exif.SamsungPreview.JPEGInterchangeFormatLength" },
            { pttIfd, "SamsungPreview"                                },
            { pttLen, "Exif.Thumbnail.StripByteCounts"                },
            { pttIfd, "Thumbnail"                                     },
            { pttLen, "Exif.Thumbnail.JPEGInterchangeFormatLength"    },
            { pttIfd, "Thumbnail"                                     }
        };
        bool delTags = false;
        for (auto&& filteredPvTag : filteredPvTags) {
            switch (filteredPvTag.ptt_) {
                case pttLen:
                {
                    delTags = false;
                    auto pos = ed.findKey(ExifKey(filteredPvTag.key_));
                    if (pos != ed.end() && sumToLong(*pos) > 32768) {
                        delTags = true;
#ifndef SUPPRESS_WARNINGS
                    EXV_WARNING << "Exif tag " << pos->key() << " not encoded\n";
#endif
                    ed.erase(pos);
                    }
                break;
                }
            case pttTag:
                {
                if (delTags) {
                    auto pos = ed.findKey(ExifKey(filteredPvTag.key_));
                    if (pos != ed.end()) {
#ifndef SUPPRESS_WARNINGS
                        EXV_WARNING << "Exif tag " << pos->key() << " not encoded\n";
#endif
                        ed.erase(pos);
                    }
                }
                break;
                }
            case pttIfd:
                if (delTags) {
#ifndef SUPPRESS_WARNINGS
                    EXV_WARNING << "Exif IFD " << filteredPvTag.key_ << " not encoded\n";
#endif
                    eraseIfd(ed, Internal::groupId(filteredPvTag.key_));
                }
                break;
            }
        }

        // Delete unknown tags larger than 4kB and known tags larger than 20kB.
        for (auto tag_iter = ed.begin(); tag_iter != ed.end(); ) {
            if ( (tag_iter->size() > 4096 && tag_iter->tagName().substr(0, 2) == "0x") ||
                  tag_iter->size() > 20480) {
#ifndef SUPPRESS_WARNINGS
                EXV_WARNING << "Exif tag " << tag_iter->key() << " not encoded\n";
#endif
                tag_iter = ed.erase(tag_iter);
            }
            else {
                ++tag_iter;
            }
        }

        // Encode the remaining Exif tags again, don't care if it fits this time
        MemIo mio2;
        wm = TiffParserWorker::encode(mio2, pData, static_cast<uint32_t>(size), ed, emptyIptc, emptyXmp, Tag::root,
                                      TiffMapping::findEncoder, &header, nullptr);
        append(blob, mio2.mmap(), static_cast<uint32_t>(mio2.size()));
#ifdef EXIV2_DEBUG_MESSAGES
        if (wm == wmIntrusive) {
            std::cerr << "SIZE OF EXIF DATA IS " << std::dec << mio2.size() << " BYTES\n";
        }
        else {
            std::cerr << "SIZE DOESN'T MATTER, NON-INTRUSIVE WRITING USED\n";
        }
#endif
        return wm;

    } // ExifParser::encode

}                                       // namespace Exiv2

// *****************************************************************************
// local definitions
namespace {

    //! @cond IGNORE
    Thumbnail::UniquePtr Thumbnail::create(const Exiv2::ExifData& exifData)
    {
        std::unique_ptr<Thumbnail> thumbnail;
        const Exiv2::ExifKey k1("Exif.Thumbnail.Compression");
        auto pos = exifData.findKey(k1);
        if (pos != exifData.end()) {
            if (pos->count() == 0)
                return thumbnail;
            auto compression = pos->toInt64();
            if (compression == 6) {
                thumbnail = std::make_unique<JpegThumbnail>();
            }
            else {
                thumbnail = std::make_unique<TiffThumbnail>();
            }
        }
        else {
            const Exiv2::ExifKey k2("Exif.Thumbnail.JPEGInterchangeFormat");
            pos = exifData.findKey(k2);
            if (pos != exifData.end()) {
                thumbnail = std::make_unique<JpegThumbnail>();
            }
        }
        return thumbnail;
    }

    const char* TiffThumbnail::mimeType() const
    {
        return "image/tiff";
    }

    const char* TiffThumbnail::extension() const
    {
        return ".tif";
    }

    Exiv2::DataBuf TiffThumbnail::copy(const Exiv2::ExifData& exifData) const
    {
        Exiv2::ExifData thumb;
        // Copy all Thumbnail (IFD1) tags from exifData to Image (IFD0) tags in thumb
        for (auto&& i : exifData) {
            if (i.groupName() == "Thumbnail") {
                std::string key = "Exif.Image." + i.tagName();
                thumb.add(Exiv2::ExifKey(key), &i.value());
            }
        }

        Exiv2::MemIo io;
        Exiv2::IptcData emptyIptc;
        Exiv2::XmpData  emptyXmp;
        Exiv2::TiffParser::encode(io, nullptr, 0, Exiv2::littleEndian, thumb, emptyIptc, emptyXmp);
        return io.read(io.size());
    }

    const char* JpegThumbnail::mimeType() const
    {
        return "image/jpeg";
    }

    const char* JpegThumbnail::extension() const
    {
        return ".jpg";
    }

    Exiv2::DataBuf JpegThumbnail::copy(const Exiv2::ExifData& exifData) const
    {
        Exiv2::ExifKey key("Exif.Thumbnail.JPEGInterchangeFormat");
        auto format = exifData.findKey(key);
        if (format == exifData.end()) return Exiv2::DataBuf();
        return format->dataArea();
    }

    int64_t sumToLong(const Exiv2::Exifdatum& md)
    {
        int64_t sum = 0;
        for (size_t i = 0; i < md.count(); ++i) {
            sum += md.toInt64(static_cast<long>(i));
        }
        return sum;
    }

    void eraseIfd(Exiv2::ExifData& ed, Exiv2::IfdId ifdId)
    {
        ed.erase(std::remove_if(ed.begin(),
                                ed.end(),
                                Exiv2::FindExifdatum(ifdId)),
                 ed.end());
    }
    //! @endcond
}  // namespace