Optical Flow HS between two Images

Hi, I'm working with the Optical Flow HS method and I would like to know how I can set the "Compute optical flow between" parameter to 'Two images'.

In the description, it says that I have to change it into 'Two images' to compute the optical Flow between images instead of video frames.

% Compute optical flow

flow = estimateFlow(opticFlow, frameGray);

This is the standard input, what exactly I have to digit to change it?

Thank you very much

Answer 1

[Hrishikesh Borate]

Hi,

The following code demonstrates the computation of optical flow between two images.

vidReader = VideoReader('visiontraffic.avi','CurrentTime',11);
frame1 = readFrame(vidReader);
% Extract 11th frame 
for i=1:10
    frame2 = readFrame(vidReader);
end
frame = {frame1, frame2};
h = figure;
movegui(h);
hViewPanel = uipanel(h,'Position',[0 0 1 1],'Title','Plot of Optical Flow Vectors');
hPlot = axes(hViewPanel);
opticFlow = opticalFlowHS;
for i=1:2
    frameRGB = frame{i};
    frameGray = im2gray(frameRGB);  
    flow = estimateFlow(opticFlow,frameGray);
    imshow(frameRGB)
    hold on
    plot(flow,'DecimationFactor',[5 5],'ScaleFactor',60,'Parent',hPlot);
    hold off
    pause(1)
end

The flow variable stores the optical flow between the two images (frame1 and frame2).

For more information, refer to the opticalFlowHS documentation.

[Vivek Raj]

Hello everyone, how i can detect current position of a ball (if i want to track a ball in image) using Horn-Schunk method?

[Image Analyst]

I'm guessing you'd threshold the flow image and then call regionprops and ask for the centroid. Attach a snippet of your video in a new question, and your code, if you still have problems.