目标检测光流法（三）：opencv下光流Farneback法

    #include <opencv2/highgui/highgui.hpp>
    #include <opencv2/imgproc/imgproc.hpp>
    #include <opencv2/video/video.hpp>
    #include <opencv2/core/core.hpp>
    #include <opencv2/imgproc/types_c.h>
    #include <iostream>
    #include <cstdio>
    
    using namespace std;
    using namespace cv;
    #define UNKNOWN_FLOW_THRESH 1e9  
    
    void makecolorwheel(vector<Scalar> &colorwheel)  
    {  
    int RY = 15;  
    int YG = 6;  
    int GC = 4;  
    int CB = 11;  
    int BM = 13;  
    int MR = 6;  
    
    int i;  
    
    for (i = 0; i < RY; i++) colorwheel.push_back(Scalar(255,       255*i/RY,     0));  
    for (i = 0; i < YG; i++) colorwheel.push_back(Scalar(255-255*i/YG, 255,       0));  
    for (i = 0; i < GC; i++) colorwheel.push_back(Scalar(0,         255,      255*i/GC));  
    for (i = 0; i < CB; i++) colorwheel.push_back(Scalar(0,         255-255*i/CB, 255));  
    for (i = 0; i < BM; i++) colorwheel.push_back(Scalar(255*i/BM,      0,        255));  
    for (i = 0; i < MR; i++) colorwheel.push_back(Scalar(255,       0,        255-255*i/MR));  
    }  
    
    void motionToColor(Mat flow, Mat &color)  
    {  
    if (color.empty())  
        color.create(flow.rows, flow.cols, CV_8UC3);  
    
    static vector<Scalar> colorwheel; //Scalar r,g,b  
    if (colorwheel.empty())  
        makecolorwheel(colorwheel);  
    
    // determine motion range:  
    float maxrad = -1;  
    
    // Find max flow to normalize fx and fy  
    for (int i= 0; i < flow.rows; ++i)   
    {  
        for (int j = 0; j < flow.cols; ++j)   
        {  
            Vec2f flow_at_point = flow.at<Vec2f>(i, j);  
            float fx = flow_at_point[0];  
            float fy = flow_at_point[1];  
            if ((fabs(fx) >  UNKNOWN_FLOW_THRESH) || (fabs(fy) >  UNKNOWN_FLOW_THRESH))  
                continue;  
            float rad = sqrt(fx * fx + fy * fy);  
            maxrad = maxrad > rad ? maxrad : rad;  
        }  
    }  
    
    for (int i= 0; i < flow.rows; ++i)   
    {  
        for (int j = 0; j < flow.cols; ++j)   
        {  
            uchar *data = color.data + color.step[0] * i + color.step[1] * j;  
            Vec2f flow_at_point = flow.at<Vec2f>(i, j);  
    
            float fx = flow_at_point[0] / maxrad;  
            float fy = flow_at_point[1] / maxrad;  
            if ((fabs(fx) >  UNKNOWN_FLOW_THRESH) || (fabs(fy) >  UNKNOWN_FLOW_THRESH))  
            {  
                data[0] = data[1] = data[2] = 0;  
                continue;  
            }  
            float rad = sqrt(fx * fx + fy * fy);  
    
            float angle = atan2(-fy, -fx) / CV_PI;  
            float fk = (angle + 1.0) / 2.0 * (colorwheel.size()-1);  
            int k0 = (int)fk;  
            int k1 = (k0 + 1) % colorwheel.size();  
            float f = fk - k0;  
            //f = 0; // uncomment to see original color wheel  
    
            for (int b = 0; b < 3; b++)   
            {  
                float col0 = colorwheel[k0][b] / 255.0;  
                float col1 = colorwheel[k1][b] / 255.0;  
                float col = (1 - f) * col0 + f * col1;  
                if (rad <= 1)  
                    col = 1 - rad * (1 - col); // increase saturation with radius  
                else  
                    col *= .75; // out of range  
                data[2 - b] = (int)(255.0 * col);  
            }  
        }  
    }  
    }  
    
    
    int main()
    {
    Mat I1;
    Mat I2;
    Mat flow;
    //读取两个图像---相邻帧
    I1 = imread("I1.jpg",0);//读取为灰度图像
    I2 = imread("I2.jpg",0);
    calcOpticalFlowFarneback(I1,I2,flow,0.5,3,20,3,5,1.2,0);
    //cout<<I1.size()<<flow.size()<<flow.at<Vec2f>(10,10)<<endl;
    //flow = abs(flow);
    Mat motion2color;  
    motionToColor(flow, motion2color);  
    imshow("flow",motion2color);
    waitKey(0);
    return 0;
    }