OpenCV写入静态图片时，imwrite函数第三个参数可以设置压缩率，默认值为95.
cv::Mat inImage= cv::imread("lena.jpg");
vector<int> compression_params;
compression_params.push_back(CV_IMWRITE_JPEG_QUALITY);
compression_params.push_back();
cv::imwrite("outImage.jpg", frame, compression_params);