Hello. I'm developing a video extensometer based on the identification of center of mass of circular white mark on a black rubber specimen. In order to deal with data in real time I have to be fast (over 100 fps). So I first identify the Zones Of Interests using this example : http://scikit-image.org/docs/dev/auto_examples/plot_label.html Then I compute the center of mass on each ZOI. As I have a fast camera the ZOI between two successive images doesn't change much. So if I extend the bounding box of my current ZOI I could be pretty confident in the fact that given circular mark in the next picture will be in the extended ZOI and the recompute an updated extened ZOI for the next image. So this is the big picture. You will find bellow the function I use in order to get it : def barycenter(image_,minx_,miny_,maxx_,maxy_,thresh_,border_): bw_=image_[minx_:maxx_+1,miny_:maxy_+1]>thresh_ [Y,X]=np.meshgrid(range(miny_,maxy_+1),range(minx_,maxx_+1)) region=regionprops(bw_) minx,miny,maxx,maxy=region[0].bbox Px_=(X*bw_).sum().astype(float)/bw_.sum() Py_=(Y*bw_).sum().astype(float)/bw_.sum() minx_=X[minx,miny]-border_ miny_=Y[minx,miny]-border_ maxx_=X[maxx,maxy]+border_ maxy_=Y[maxx,maxy]+border_ return Px_,Py_,minx_,miny_,maxx_,maxy_ As you can see I don't use region[0].centroid. I compute the moment myself if I time my function on a 141x108 ZOI I get 504 µs If I time this function : def barycenter2(image_,minx_,miny_,maxx_,maxy_,thresh_,border_): bw_=image_[minx_:maxx_+1,miny_:maxy_+1]>thresh_ [Y,X]=np.meshgrid(range(miny_,maxy_+1),range(minx_,maxx_+1)) region=regionprops(bw_) Px_,Py_=region[0].centroid Px_+=minx_ Py_+=miny_ minx,miny,maxx,maxy=region[0].bbox minx_=X[minx,miny]-border_ miny_=Y[minx,miny]-border_ maxx_=X[maxx,maxy]+border_ maxy_=Y[maxx,maxy]+border_ return Px_,Py_,minx_,miny_,maxx_,maxy_ I get 10ms per loop ! What is really strange is if I time : %timeit region[0].centroid I get 58.6 ns per loop ! So I don't really understand why this time explose when I use it in a function ? If someone have some insight it will be very helpfull. Even If I can use my first function, it's a pity to have to use less optimized functions. Best regards.