mrwthumb.cpp

Sample program to extract a Minolta thumbnail from the makernote

// ***************************************************************** -*- C++ -*-
// mrwthumb.cpp
// Sample program to extract a Minolta thumbnail from the makernote

#include "error.hpp"
#include "exif.hpp"
#include "image.hpp"

#include <cassert>
#include <iostream>

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

        Exiv2::Image::AutoPtr image = Exiv2::ImageFactory::open(argv[1]);
        assert(image.get() != 0);
        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::kerErrorMessage, error);
        }

        Exiv2::ExifKey key("Exif.Minolta.ThumbnailOffset");
        Exiv2::ExifData::const_iterator format = exifData.findKey(key);

        if (format != exifData.end()) {
            Exiv2::DataBuf buf = format->dataArea();

            // The first byte of the buffer needs to be patched
            buf.pData_[0] = 0xff;

            Exiv2::FileIo file("img_thumb.jpg");

            file.open("wb");
            file.write(buf.pData_, buf.size_);
            file.close();
        }

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