Add sample of sparse pyrlk optical flow thread safe

samples/gpu/pyrlk_optical_flow_multithreading.cpp

+#include <iostream>
+#include <vector>
+#include <sstream>
+
+#include "opencv2/core/core.hpp"
+#include "cvconfig.h"
+
+#ifdef HAVE_TBB
+#include <tbb/parallel_for_each.h>
+#include <tbb/task_scheduler_init.h>
+
+#include "opencv2/imgproc/imgproc.hpp"
+#include "opencv2/highgui/highgui.hpp"
+#include "opencv2/video/video.hpp"
+#include "opencv2/gpu/gpu.hpp"
+
+using namespace std;
+using namespace cv;
+using namespace cv::gpu;
+
+static void download(const GpuMat& d_mat, vector<Point2f>& vec)
+{
+    vec.resize(d_mat.cols);
+    Mat mat(1, d_mat.cols, CV_32FC2, (void*)&vec[0]);
+    d_mat.download(mat);
+}
+
+static void download(const GpuMat& d_mat, vector<uchar>& vec)
+{
+    vec.resize(d_mat.cols);
+    Mat mat(1, d_mat.cols, CV_8UC1, (void*)&vec[0]);
+    d_mat.download(mat);
+}
+
+static void drawArrows(Mat& frame, const vector<Point2f>& prevPts, const vector<Point2f>& nextPts, const vector<uchar>& status, Scalar line_color = Scalar(0, 0, 255))
+{
+    for (size_t i = 0; i < prevPts.size(); ++i)
+    {
+        if (status[i])
+        {
+            int line_thickness = 1;
+
+            Point p = prevPts[i];
+            Point q = nextPts[i];
+
+            double angle = atan2((double) p.y - q.y, (double) p.x - q.x);
+
+            double hypotenuse = sqrt( (double)(p.y - q.y)*(p.y - q.y) + (double)(p.x - q.x)*(p.x - q.x) );
+
+            if (hypotenuse < 1.0)
+                continue;
+
+            // Here we lengthen the arrow by a factor of three.
+            q.x = (int) (p.x - 3 * hypotenuse * cos(angle));
+            q.y = (int) (p.y - 3 * hypotenuse * sin(angle));
+
+            // Now we draw the main line of the arrow.
+            line(frame, p, q, line_color, line_thickness);
+
+            // Now draw the tips of the arrow. I do some scaling so that the
+            // tips look proportional to the main line of the arrow.
+
+            p.x = (int) (q.x + 9 * cos(angle + CV_PI / 4));
+            p.y = (int) (q.y + 9 * sin(angle + CV_PI / 4));
+            line(frame, p, q, line_color, line_thickness);
+
+            p.x = (int) (q.x + 9 * cos(angle - CV_PI / 4));
+            p.y = (int) (q.y + 9 * sin(angle - CV_PI / 4));
+            line(frame, p, q, line_color, line_thickness);
+        }
+    }
+}
+
+template <typename T> inline T clamp (T x, T a, T b)
+{
+    return ((x) > (a) ? ((x) < (b) ? (x) : (b)) : (a));
+}
+
+template <typename T> inline T mapValue(T x, T a, T b, T c, T d)
+{
+    x = clamp(x, a, b);
+    return c + (d - c) * (x - a) / (b - a);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+////////////////////////////////////////////////////////////////////////////////
+struct S_Thread_data
+{
+    Size winSize;
+    int maxLevel;
+    int iters;
+
+    Stream stream;
+    Mat frame0;
+    Mat frame1;
+    Mat frame1Gray;
+
+    GpuMat d_frame0Gray;
+    GpuMat d_prevPts;
+    bool useGray;
+};
+
+struct pyrLK_task
+{
+    pyrLK_task(size_t n):
+        _n(n),
+        _thread_data(NULL){}
+
+    void operator()()
+    {
+        // Sparse
+
+        PyrLKOpticalFlow d_pyrLK;
+
+        d_pyrLK.winSize.width = _thread_data->winSize.width;
+        d_pyrLK.winSize.height = _thread_data->winSize.height;
+        d_pyrLK.maxLevel = _thread_data->maxLevel;
+        d_pyrLK.iters = _thread_data->iters;
+
+        GpuMat d_frame0(_thread_data->frame0);
+        GpuMat d_frame1(_thread_data->frame1);
+        GpuMat d_frame1Gray(_thread_data->frame1Gray);
+        GpuMat d_nextPts;
+        GpuMat d_status;
+
+        bool useGray = _thread_data->useGray;
+
+        d_pyrLK.sparse_multi(useGray ? _thread_data->d_frame0Gray : d_frame0,
+                    useGray ? d_frame1Gray : d_frame1,
+                            _thread_data->d_prevPts, d_nextPts,
+                    d_status, _thread_data->stream, NULL);
+
+        // Draw arrows
+
+        vector<Point2f> prevPts(_thread_data->d_prevPts.cols);
+        download(_thread_data->d_prevPts, prevPts);
+
+        vector<Point2f> nextPts(d_nextPts.cols);
+        download(d_nextPts, nextPts);
+
+        vector<uchar> status(d_status.cols);
+        download(d_status, status);
+
+        drawArrows(_thread_data->frame0, prevPts, nextPts, status, Scalar(255, 0, 0));
+    }
+
+    size_t _n;
+    struct S_Thread_data* _thread_data;
+};
+
+template <typename T> struct invoker {
+  void operator()(T& it) const {it();}
+};
+
+#define THREADS_NB    12
+
+int main(int argc, const char* argv[])
+{
+    const char* keys =
+        "{ h            | help           | false | print help message }"
+        "{ l            | left           |       | specify left image }"
+        "{ r            | right          |       | specify right image }"
+        "{ gray         | gray           | false | use grayscale sources [PyrLK Sparse] }"
+        "{ win_size     | win_size       | 21    | specify windows size [PyrLK] }"
+        "{ max_level    | max_level      | 3     | specify max level [PyrLK] }"
+        "{ iters        | iters          | 30    | specify iterations count [PyrLK] }"
+        "{ points       | points         | 4000  | specify points count [GoodFeatureToTrack] }"
+        "{ min_dist     | min_dist       | 0     | specify minimal distance between points [GoodFeatureToTrack] }";
+
+    CommandLineParser cmd(argc, argv, keys);
+
+    if (cmd.get<bool>("help"))
+    {
+        cout << "Usage: pyrlk_optical_flow_multithreading [options]" << endl;
+        cout << "Avaible options:" << endl;
+        cmd.printParams();
+        return 0;
+    }
+
+    string fname0 = cmd.get<string>("left");
+    string fname1 = cmd.get<string>("right");
+
+    if (fname0.empty() || fname1.empty())
+    {
+        cerr << "Missing input file names" << endl;
+        return -1;
+    }
+
+    bool useGray = cmd.get<bool>("gray");
+    int winSize = cmd.get<int>("win_size");
+    int maxLevel = cmd.get<int>("max_level");
+    int iters = cmd.get<int>("iters");
+    int points = cmd.get<int>("points");
+    double minDist = cmd.get<double>("min_dist");
+
+    Mat frame0 = imread(fname0);
+    Mat frame1 = imread(fname1);
+
+    if (frame0.empty() || frame1.empty())
+    {
+        cout << "Can't load input images" << endl;
+        return -1;
+    }
+
+    cout << "Image size : " << frame0.cols << " x " << frame0.rows << endl;
+    cout << "Points count : " << points << endl;
+
+    cout << endl;
+
+    Mat frame0Gray;
+    cvtColor(frame0, frame0Gray, COLOR_BGR2GRAY);
+    Mat frame1Gray;
+    cvtColor(frame1, frame1Gray, COLOR_BGR2GRAY);
+
+    // goodFeaturesToTrack
+
+    GoodFeaturesToTrackDetector_GPU detector(points, 0.01, minDist);
+
+    GpuMat d_frame0Gray(frame0Gray);
+    GpuMat d_prevPts;
+
+    detector(d_frame0Gray, d_prevPts);
+
+    // Sparse
+
+    tbb::task_scheduler_init init(THREADS_NB);
+
+    std::vector<pyrLK_task> tasks;
+
+    S_Thread_data s_thread_data[THREADS_NB];
+
+    for (unsigned int uiI = 0; uiI < THREADS_NB; ++uiI)
+    {
+        s_thread_data[uiI].stream = Stream();
+        s_thread_data[uiI].frame0 = frame0.clone();
+        s_thread_data[uiI].frame1 = frame1.clone();
+        s_thread_data[uiI].frame1Gray = frame0Gray.clone();
+
+        s_thread_data[uiI].iters = iters;
+        s_thread_data[uiI].useGray = useGray;
+        s_thread_data[uiI].maxLevel = maxLevel;
+        s_thread_data[uiI].winSize.height = winSize;
+        s_thread_data[uiI].winSize.width = winSize;
+        s_thread_data[uiI].d_frame0Gray = d_frame0Gray.clone();
+        s_thread_data[uiI].d_prevPts = d_prevPts.clone();
+
+        tasks.push_back(pyrLK_task(uiI));
+        tasks.back()._thread_data = &(s_thread_data[uiI]);
+    }
+
+    tbb::parallel_for_each(tasks.begin(),tasks.end(),invoker<pyrLK_task>());
+
+    for (unsigned int uiI = 0; uiI < THREADS_NB; ++uiI)
+    {
+        stringstream ss;
+        ss << "PyrLK MultiThreading [Sparse] " << uiI;
+
+        imshow(ss.str(), s_thread_data[uiI].frame0);
+        ss.str("");
+    }
+
+    waitKey();
+
+    return 0;
+}
+#else
+int main(int , const char* [])
+{
+    std::cout << "This example pyrlk_optical_flow_multithreading must be compiled with TBB Option" << std::endl;
+    return 0;
+}
+#endif // HAVE_TBB