opencv imdecode和imencode用法

主要是对内存数据自动编解码

    string fname = "D:/image.jpg";
    //! 以二进制流方式读取图片到内存
    FILE* pFile = fopen(fname.c_str(), "rb");
    fseek(pFile, 0, SEEK_END);
    long lSize = ftell(pFile);
    rewind(pFile);
    char* pData = new char[lSize];
    fread(pData, sizeof(char), lSize, pFile);
    fclose(pFile);

    //! 解码内存数据，变成cv::Mat数据
    cv::Mat img_decode;
    vector<uchar> data;
    for (int i = 0; i < lSize; ++i){
        data.push_back(pData[i]);
    }
    img_decode = cv::imdecode(data, CV_LOAD_IMAGE_COLOR);
    cv::flip(img_decode, img_decode, -1);
    img_decode.channels();

    //! 将cv::Mat数据编码成数据流
    vector<unsigned char> img_encode;
    cv::imencode(".jpg", img_decode, img_encode);
    unsigned char *encode_data = new unsigned char[lSize];
    for (int i = 0; i<lSize; i++){
        encode_data[i] = img_encode[i];
    }