Computing centroid of a detection box after computing NCC between a template image and another image

Currently I am working on an object tracking project and I am using template matching to find my "measured position" of my object. I have a template image of my object which then I am computing NCC (normalized cross correlation) between the template and image, then a detection box is drawn on the object I am trying to track in the image. I would like to compute the centroid of the detection box to use it as an estimate for the "measured position" (so get an x and y coordinate in the image) but currently i keep getting the following error and I am not sure what is wrong.

Error using regionprops

Expected input number 1, L, to be one of these types:

uint8, uint16, uint32, int8, int16, int32, single, double, categorical

Instead its type was images.roi.Rectangle.

Error in regionprops (line 236)

validateattributes(L, supportedTypes, supportedAttributes, ...

The following is my code:

dog = im2gray(imread('108.jpg'));
temp = im2gray(imread('template6.jpg'));
montage({dog,temp})
c = normxcorr2(temp,dog);
surf(c)
figure;
plot(c);
shading flat
[ypeak,xpeak] = find(c==max(c(:)));
yoffSet = ypeak-size(temp,1);
xoffSet = xpeak-size(temp,2);
imshow(dog)
v = drawrectangle(gca,'Position',[xoffSet,yoffSet,size(temp,2),size(temp,1)], ...
    'FaceAlpha',0);
Ibw = im2bw(dog);
Ibw = imfill(Ibw,'holes');
stat = regionprops(v,'centroid');
for x = 1: numel(stat)
    plot(stat(x).Centroid(1),stat(x).Centroid(2),'ro');
end

I appreciate the help guys!

Answer 1

[Matt J]

Centroid=[xoffSet,yoffSet] + [size(temp,2),size(temp,1)]/2;

plot(Centroid(:,1),Centroid(:,2),'ro');

[Nizar Sharkas]

so I tried that, and used hold so I can have the centroid plotted onto this image, but when I use the above lines I no longer get the detection box and the centroid is in a seperate plot rather on the same image with the detection box

[Matt J]

Instead of summarizing for us what you did and the results you got, you should get into the habit of running your code directly in your post, as I have done below. That will give us a full picture of what is happening. In any case, my example below should clarify what steps are needed and the result you can expect.

[x,y,h,w]=deal(50,20,20,30);

imshow(imread('cameraman.tif'));

drawrectangle(gca,'Position',[x,y,h,w], 'FaceAlpha',0);

Centroid=[x,y]+[h,w]/2;

hold on
plot(Centroid(:,1),Centroid(:,2),'ro','MarkerFaceColor','y');
hold off

[Nizar Sharkas]

I will do that, thanks a bunch

Answer 2

[Image Analyst]

Please attach your images with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

so I can run your code.

In the meantime, see how I do it in the attached demo.

v is not a binary image or a labeled image like regionprops want. You need to make a mask

[rows, columns, numberOfColorChannels] = size(dog)
y1 = ypeak-size(temp,1);
x1 = xpeak-size(temp,2);
y2 = ypeak+size(temp,1);
x2 = xpeak+size(temp,2);
mask = false(rows, columns);
mask(y1:y2, x1:x2) = true;

[Nizar Sharkas]

[Nizar Sharkas]

I would like to amend my code to where the I can get the centroid coordinates (x and y) of the detection box (in blue). Also, if i wanted to see the coordinates of the box's corners, how can I do that?

Thanks a bunch!

[Image Analyst]

I think you totally overlooked my answer. Did you see the part where I said:

Please attach your images with the paperclip icon after you read this:

TUTORIAL: How to ask a question (on Answers) and get a fast answer

so I can run your code.

That is one way. How else can we work with your images? I don't want screenshots either. I want the actual .PNG files. Both the main scene and te target/template file.