Code for OpenCV >= 3

[sudonto]

Code snippet using OpenCV >= 3 version:

        cv::Mat image, prev_image, prev_grey, grey, frame, flow, flows[2];
    cv::cuda::GpuMat frame_0, frame_1, gflow;

    cv::cuda::setDevice(chrDevID);

    cv::Ptr<cv::cuda::OpticalFlowDual_TVL1> alg_tvl1 = cv::cuda::OpticalFlowDual_TVL1::create();
    cv::Ptr<cv::cuda::FarnebackOpticalFlow> alg_farn = cv::cuda::FarnebackOpticalFlow::create();
    cv::Ptr<cv::cuda::BroxOpticalFlow> alg_brox = cv::cuda::BroxOpticalFlow::create();

    while (true) {
        capture >> frame;
        if (frame.empty())
            break;
        if (intFrameNum == 0) {
            image.create(frame.size(), CV_8UC3);
            grey.create(frame.size(), CV_8UC1);
            prev_image.create(frame.size(), CV_8UC3);
            prev_grey.create(frame.size(), CV_8UC1);

            frame.copyTo(prev_image);
            cv::cvtColor(prev_image, prev_grey, cv::COLOR_BGR2GRAY);

            intFrameNum++;

            int intStep_t = intStep;
            while (intStep_t > 1) {
                capture >> frame;
                intStep_t--;
            }
            continue;
        }

        frame.copyTo(image);
        cv::cvtColor(image, grey, cv::COLOR_BGR2GRAY);

        frame_0.upload(prev_grey);
        frame_1.upload(grey);

        // GPU optical flow
        switch (intType) {
        case 0:
            alg_farn->calc(frame_0, frame_1, gflow);
            break;
        case 1:
            alg_tvl1->calc(frame_0, frame_1, gflow);
            break;
        case 2:
            cv::cuda::GpuMat d_frame0f, d_frame1f;
            frame_0.convertTo(d_frame0f, CV_32F, 1.0 / 255.0);
            frame_1.convertTo(d_frame1f, CV_32F, 1.0 / 255.0);
            alg_brox->calc(d_frame0f, d_frame1f, gflow);
            break;
        }

        gflow.download(flow);
        cv::split(flow, flows);

        // Output optical flow
        cv::Mat imgX(flows[0].size(), CV_8UC1);
        cv::Mat imgY(flows[1].size(), CV_8UC1);
        convertFlowToImage(flows[0], flows[1], imgX, imgY, -intBound, intBound);
        char chrSuffix[20];
        sprintf_s(chrSuffix, "_%06d.jpg", int(intFrameNum));

        cv::Mat imgX_, imgY_, image_;
        intHeight = (intHeight > 0) ? intHeight : imgX.rows;
        intWidth = (intWidth  > 0) ? intWidth : imgX.cols;
        resize(imgX, imgX_, cv::Size(intWidth, intHeight));
        resize(imgY, imgY_, cv::Size(intWidth, intHeight));
        resize(image, image_, cv::Size(intWidth, intHeight));

        //cv::namedWindow("image", cv::WINDOW_AUTOSIZE);
        //cv::imshow("image", imgY_);
        //cv::waitKey(20);

        cv::imwrite(strSavePath + strXFlowFile + chrSuffix, imgX_);
        cv::imwrite(strSavePath + strYFlowFile + chrSuffix, imgY_);
        cv::imwrite(strSavePath + strImgFile + chrSuffix, image_);