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mrwthumb.cpp

Sample program to extract a Minolta thumbnail from the makernote

// SPDX-License-Identifier: GPL-2.0-or-later
// Sample program to extract a Minolta thumbnail from the makernote
#include <exiv2/exiv2.hpp>
#include <iostream>
int main(int argc, char* const argv[]) {
Exiv2::XmpParser::initialize();
::atexit(Exiv2::XmpParser::terminate);
try {
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();
if (exifData.empty()) {
std::string error(argv[1]);
error += ": No Exif data found in the file";
throw Exiv2::Error(Exiv2::ErrorCode::kerErrorMessage, error);
}
Exiv2::ExifKey key("Exif.Minolta.ThumbnailOffset");
auto format = exifData.findKey(key);
if (format != exifData.end()) {
Exiv2::DataBuf buf = format->dataArea();
// The first byte of the buffer needs to be patched
buf.write_uint8(0, 0xff);
Exiv2::FileIo file("img_thumb.jpg");
file.open("wb");
file.write(buf.c_data(), buf.size());
file.close();
}
return EXIT_SUCCESS;
} catch (Exiv2::Error& e) {
std::cout << "Caught Exiv2 exception '" << e << "'\n";
return EXIT_FAILURE;
}
}
Exiv2::Error
Simple error class used for exceptions. An output operator is provided to print errors to a stream.
Definition error.hpp:236
Exiv2::ExifData
A container for Exif data. This is a top-level class of the Exiv2 library. The container holds Exifda...
Definition exif.hpp:379
Exiv2::ExifData::empty
bool empty() const
Return true if there is no Exif metadata.
Definition exif.hpp:465
Exiv2::ExifData::findKey
iterator findKey(const ExifKey &key)
Find the first Exifdatum with the given key, return an iterator to it.
Definition exif.cpp:466
Exiv2::ExifData::end
iterator end()
End of the metadata.
Definition exif.hpp:439
Exiv2::ExifKey
Concrete keys for Exif metadata and access to Exif tag reference data.
Definition tags.hpp:271
Exiv2::FileIo
Provides binary file IO by implementing the BasicIo interface.
Definition basicio.hpp:284
Exiv2::FileIo::open
int open(const std::string &mode)
Open the file using the specified mode.
Exiv2::FileIo::write
size_t write(const byte *data, size_t wcount) override
Write data to the file. The file position is advanced by the number of bytes written.
Exiv2::FileIo::close
int close() override
Flush and unwritten data and close the file . It is safe to call close on an already closed instance.
Exiv2::ImageFactory::open
static Image::UniquePtr open(const std::string &path, bool useCurl=true)
Create an Image subclass of the appropriate type by reading the specified file. Image type is derived...
Definition image.cpp:820
Exiv2::XmpParser::initialize
static bool initialize(XmpParser::XmpLockFct xmpLockFct=nullptr, void *pLockData=nullptr)
Initialize the XMP Toolkit.
Definition xmp.cpp:568
Exiv2::XmpParser::terminate
static void terminate()
Terminate the XMP Toolkit and unregister custom namespaces.
Definition xmp.cpp:623
Exiv2::DataBuf
Utility class containing a character array. All it does is to take care of memory allocation and dele...
Definition types.hpp:124
Exiv2::DataBuf::c_data
const byte * c_data(size_t offset=0) const
Returns a (read-only) data pointer.
Definition types.cpp:179