MATLAB: Discarding certain centroids found using regionprops

centroidregionprops

Hi, I work with time sequence images. I process and threshold these images to get a black image with some scattered white spots. I want to track these white spots as a function of time and I want to use their centroids to do so.
I am using the functions 'bwlabel' and 'regionprops' to find the centroid and area of the white spots. The problem I am facing is that regionprops also computes the centroids and areas of certain small white specks that are in the black region of my image. I see that all of these points have a unit area. These specks may be just noise.
Hence I was wondering if someone could tell me what function I could use to remove these unwanted points. I know their areas and their position in the regionprops matrix.
Thanks
NS
If 'I' is my processed double image, my code is as follows:
L=bwlabel(I);
s=regionprops(L,'Centroid','Area');

Best Answer

What do you mean it computes the centroid parts in a black area? There's no way that it does that.
It's possible the centroid of a blob isn't in the blob. But it's definitely not calculating centroids for the background. If you think of a blob in the shape of "U", the centroid will not lie in on the U.
If you want to keep only centroids that occur in the area of a blob, that's easily possible.
EDIT Per comment/clarification:
I would just use bwareaopen on your logical image to remove small blobs.
I = bwareaopen(I,10); %all objects with fewer than 10px gone.
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