MATLAB: I want to detect a change in centroid (both in x and y axis separtely) of two consecutive snapshots in a video in order to control a toy car using specfic colour object detection technique.

arduinoimage processing

vid = videoinput(camera_name, camera_id, format);
% Set the properties of the video object
set(vid, 'FramesPerTrigger', Inf);
set(vid, 'ReturnedColorspace', 'rgb')
vid.FrameGrabInterval = 5;
%start the video aquisition here
start(vid)
 %a=arduino('COM6');
% Set a loop that stop after 100 frames of aquisition
while(vid.FramesAcquired<=200)
      % Get the snapshot of the current frame
      data = getsnapshot(vid);
      % Now to track red objects in real time
      % we have to subtract the red component 
      % from the grayscale image to extract the red components in the image.
      diff_im = imsubtract(data(:,:,1), rgb2gray(data));
      %Use a median filter to filter out noise
      diff_im = medfilt2(diff_im, [3 3]);
      % Convert the resulting grayscale image into a binary image.
      diff_im = im2bw(diff_im,0.18);
      % Remove all those pixels less than 300px
      diff_im = bwareaopen(diff_im,300);
      % Label all the connected components in the image.
      bw = bwlabel(diff_im, 8);
      % Here we do the image blob analysis.
      % We get a set of properties for each labeled region.
      stats = regionprops(bw, 'BoundingBox', 'Centroid');
      AllCentroids = vertcat(stats.Centroid)
      % Display the image
      imshow(data)
      hold on
      %This is a loop to bound the red objects in a rectangular box.
      for object = 1:length(stats)
          bb = stats(object).BoundingBox;
          bc = stats(object).Centroid;
          rectangle('Position',bb,'EdgeColor','r','LineWidth',2)
          plot(bc(1),bc(2), '-m+');
          a=text(bc(1)+15,bc(2), strcat('X: ', num2str(round(bc(1))), '    Y: ', num2str(round(bc(2)))));
          set(a, 'FontName', 'Arial', 'FontWeight', 'bold', 'FontSize', 12, 'Color', 'yellow');
      end
above is the code which i have used to detect and track the specific colour object. now i want the centroid coordinates separately in a variable so that i can pass that data to arduino board to drive my toy car through specific colour using iamge processing tech ique.

Best Answer

In the loop, you need this:
bc = stats(object).Centroid;
xCentroid(object) = bc(1);
yCentroid(object) = bc(2);
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