Plot graph from tracked points in 2D pictures

In some Video i tracked an moving object. I extract the width and height in pixels and set these values as limit for my plot diagram. Now i want to get the tracked points in the diagram.

What I'm currently doing:

% read, track, display points and results in each frame

while hasFrame(videoReader)

frame = readFrame(videoReader);

[points,validity] = tracker(frame);

out = insertMarker(frame,points(validity, :),'+');

writeVideo(v1, out);

videoPlayer(out);

end

close(v1);

release(videoPlayer);

% draw diagram with position of tracked markers as graph

plot(points(:,1),points(:,2));

xlim([0 imageWidth])

ylim([0 imageHeight])

imageWidth and imageHeight are getting extracted from the first frame. The plotting is actually showing something, but the graph is not corresponding to my real tracked points. The Image is a 2D image, like looking from top on a table. So i only need x and y coordinates in pixels of the points and plot them.

What am I doing wrong?

Answer 1

[Image Analyst]

Are you sure points is in the form (x,y) and not (row, column) because if it were the plot would be rotated 90 degrees.

Why not display the last frame and plot the points over it?

imshow(frame);
hold on
axis('on', 'image')
plot(points(:,1), points(:,2), 'r.-', 'LineWidth', 2, 'MarkerSize', 30);

[Henning]

oh yes, you are absolutely right.

Your solution works perfect and indeed loks great. Thanks for the quick answer. I am new to MATLAB so i had no idea :D

[Image Analyst]

OK, then can you please click the "Accept this answer" link? Thanks in advance. 🙂