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# drawOpticalFlow

jet47 Dec 3rd, 2012 316 Never
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1. inline bool isFlowCorrect(Point2f u)
2. {
3.     return !cvIsNaN(u.x) && !cvIsNaN(u.y) && fabs(u.x) < 1e9 && fabs(u.y) < 1e9;
4. }
5.
6. static Vec3b computeColor(float fx, float fy)
7. {
8.     static bool first = true;
9.
10.     // relative lengths of color transitions:
11.     // these are chosen based on perceptual similarity
12.     // (e.g. one can distinguish more shades between red and yellow
13.     //  than between yellow and green)
14.     const int RY = 15;
15.     const int YG = 6;
16.     const int GC = 4;
17.     const int CB = 11;
18.     const int BM = 13;
19.     const int MR = 6;
20.     const int NCOLS = RY + YG + GC + CB + BM + MR;
21.     static Vec3i colorWheel[NCOLS];
22.
23.     if (first)
24.     {
25.         int k = 0;
26.
27.         for (int i = 0; i < RY; ++i, ++k)
28.             colorWheel[k] = Vec3i(255, 255 * i / RY, 0);
29.
30.         for (int i = 0; i < YG; ++i, ++k)
31.             colorWheel[k] = Vec3i(255 - 255 * i / YG, 255, 0);
32.
33.         for (int i = 0; i < GC; ++i, ++k)
34.             colorWheel[k] = Vec3i(0, 255, 255 * i / GC);
35.
36.         for (int i = 0; i < CB; ++i, ++k)
37.             colorWheel[k] = Vec3i(0, 255 - 255 * i / CB, 255);
38.
39.         for (int i = 0; i < BM; ++i, ++k)
40.             colorWheel[k] = Vec3i(255 * i / BM, 0, 255);
41.
42.         for (int i = 0; i < MR; ++i, ++k)
43.             colorWheel[k] = Vec3i(255, 0, 255 - 255 * i / MR);
44.
45.         first = false;
46.     }
47.
48.     const float rad = sqrt(fx * fx + fy * fy);
49.     const float a = atan2(-fy, -fx) / (float)CV_PI;
50.
51.     const float fk = (a + 1.0f) / 2.0f * (NCOLS - 1);
52.     const int k0 = static_cast<int>(fk);
53.     const int k1 = (k0 + 1) % NCOLS;
54.     const float f = fk - k0;
55.
56.     Vec3b pix;
57.
58.     for (int b = 0; b < 3; b++)
59.     {
60.         const float col0 = colorWheel[k0][b] / 255.f;
61.         const float col1 = colorWheel[k1][b] / 255.f;
62.
63.         float col = (1 - f) * col0 + f * col1;
64.
66.             col = 1 - rad * (1 - col); // increase saturation with radius
67.         else
68.             col *= .75; // out of range
69.
70.         pix[2 - b] = static_cast<uchar>(255.f * col);
71.     }
72.
73.     return pix;
74. }
75.
76. static void drawOpticalFlow(const Mat_<Point2f>& flow, Mat& dst, float maxmotion = -1)
77. {
78.     dst.create(flow.size(), CV_8UC3);
79.     dst.setTo(Scalar::all(0));
80.
81.     // determine motion range:
83.
84.     if (maxmotion <= 0)
85.     {
87.         for (int y = 0; y < flow.rows; ++y)
88.         {
89.             for (int x = 0; x < flow.cols; ++x)
90.             {
91.                 Point2f u = flow(y, x);
92.
93.                 if (!isFlowCorrect(u))
94.                     continue;
95.
97.             }
98.         }
99.     }
100.
101.     for (int y = 0; y < flow.rows; ++y)
102.     {
103.         for (int x = 0; x < flow.cols; ++x)
104.         {
105.             Point2f u = flow(y, x);
106.
107.             if (isFlowCorrect(u))