Hi,
To use "pdist" to track the balls and measure their distance traveled, you can calculate the pairwise Euclidean distance between the centroids in both frames using "pdist" and then match the closest centroids between the frames. To match the centroids, you can use the "matchpairs" function, which finds the indices of the closest pairs of points.
% Read the video
v = VideoReader('V.mp4');
% Initialize variables
centroids = cell(1, v.NumFrames);
distances = zeros(1, v.NumFrames-1);
% Loop over all frames
for i = 1:v.NumFrames
% Read the current frame
frame = read(v, i);
% Convert to binary
bw = im2bw(frame, 0.2);
bw = ~bw;
% Erode
se1 = strel('disk', 5, 0);
bw = imerode(bw, se1);
% Dilate
se2 = strel('disk', 5, 0);
bw = imdilate(bw, se2);
% Remove small objects
bw = bwareaopen(bw, 100);
% Clear border
bw = imclearborder(bw);
% Find centroids
c = regionprops(bw, 'Centroid');
centroids{i} = cat(1, c.Centroid);
end
% Loop over all frames except the last one
for i = 1:v.NumFrames-1
% Match centroids between frames
pairs = matchpairs(centroids{i}, centroids{i+1});
matched1 = centroids{i}(pairs(:,1),:);
matched2 = centroids{i+1}(pairs(:,2),:);
% Calculate pairwise distances
d = pdist2(matched1, matched2);
% Calculate total distance traveled
distances(i) = sum(d(:));
end
To apply this code to the full length of the video, you can simply remove the frame indices from the "read" function and let it read all frames:
