How to obtain velocity and magnitude vectors of the optical flow field? I am using Lucas-Kande method of optical flow.
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I am working on the following code.
n=0;
folder = fileparts(which('viptraffic.avi'));
movieFullFileName = fullfile(folder, 'viptraffic.avi');
vidReader = VideoReader(movieFullFileName);
opticFlow = opticalFlowLK('NoiseThreshold',0.0039);
while hasFrame(vidReader)
frameRGB = readFrame(vidReader);
frameGray = rgb2gray(frameRGB);
flow = estimateFlow(opticFlow,frameGray);
H=imag(flow)
V=real(flow)
frameWithFlow = getframe(gca);
imshow(frameRGB);
imshow(frameWithFlow.cdata)
hold on
plot(flow,'DecimationFactor',[5 5], 'ScaleFactor',10)
hold off
n=n+1;
end
Is there a way to get the optical flow estimates of velocity and magnitude for every optical flow field obtained in every image?
1 comentario
Nachiket Patki
el 5 de Mayo de 2018
hey @ Daksh Agarwal I also tried this code can you please tell me one thing whether your output video runs very slowly? Because I am facing that problem. How can I make it faster?
Respuestas (1)
Vishnu Sreekumar
el 1 de Mzo. de 2017
If you're still looking for an answer:
x_vel = flow.Vx;
y_vel = flow.Vy;
magnitudes = flow.Magnitude;
orientations = flow.Orientation;
Note that if the image is n x m (n rows, m columns), X direction is top to bottom and Y direction is left to right when using imshow and
plot(flow,'DecimationFactor',[5 5], 'ScaleFactor',10)
is the same as
quiver(1:n,1:m,x_vel,y_vel);
3 comentarios
Cheuk Wing Edmond Lam
el 24 de Jun. de 2018
do you happen to know the units of the values reported by flow.Magnitude?
Vishnu Sreekumar
el 18 de Jun. de 2019
@Cheuk: No but I imagine it is pixels traveled per timeframe.
So if your magnitude is 0.4, and the distance between pixels is 1 cm (depending on your specific application), and the timestep between two frames is 0.1 s, then the speed is 0.4 x 1 cm / 0.1 s = 4 cm/s.
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