MATLAB: Finding Centroids using text inserter

Question

Hello everyone, I wanted to ask a question about the vision.TextInserter. The following is some basic codes:

blob = vision.BlobAnalysis('CentroidOutputPort', true, 'AreaOutputPort',... 
                            false,'BoundingBoxOutputPort', false,'MinimumBlobAreaSource', 'Property',... 
                            'MinimumBlobArea', 20000);
textinCentroid = vision.TextInserter('Text', 'X:%4d, Y:%4d', ... 
                                    'LocationSource', 'Input port', ...
                                    'Color', [1 0 0], ... 
                                    'FontSize', 14);
while ~isDone(videoReader)
frame = step(videoReader);
I = finalimage; %Final result of image after process
centroid = step(blob, I);
result = step(textinCentroid, frame, centroid)
step(videoPlayer, result);
end

So the problem is that I got the following problem:

Error using vision.TextInserter/step
Not enough input arguments; expected 3 (in addition
to the object handle), got 2.
Error in ComputerVision2 (line 64)
     result = step(textinCentroid, frame,
     centroids);

So can anyone tell me what exactly am I missing here? What do I have to add to make it in such a way that my object detected have a centroid on it? Thank you.

Answer 1

You need the object first. You need the image second. Subtotal 2

You used %-style sequences in your string, so you need a vector of values, one per % in the string. You also need the location for the input port. Subtotal 2.

Total 4.

What I do not see documented is which order to use if you have both loc and vars. Experiment. I'm going to guess loc should be first.