// http://vision.middlebury.edu/flow/data/
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);
// 确定运动范围:
float maxrad = -1;
// 找到最大流量来规范化fx和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];