MATLAB: Algorithm used to find centroids in regionprops.

algorithmcentroidsimage processingImage Processing Toolboxregionprops

I used regionprops to find centroids in image processing. But now I have to put algorithm to show how code works to find these centroids. Someone please tell me the algorithm used for the same.

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It's a good question but I don't know that we have an answer. I know the area from regionprops is simply the pixel count, because it says so, unlike bwarea which gives the area differently depending on how many pixels are on the outer edge of the blob. Now the unweighted centroid formula is normally just the average of the x and y coordinates of all the pixels in the blob, but whether they weight pixels differently depending on whether they are near the edge (background) is not stated.

Another flavor of centroid, the weighted centroid is just sum(g*x)/sum(g) - where g is the gray level. Note how the g "cancels out" so you're left with something with units of x. The weighted centroid may be further weighted by whether a pixel is near the edge. That said, I don't think they weight pixels differently depending on their adjacency to an edge like they do for bwarea(), though I'm not 100% sure.

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MATLAB: Total area of a region of binary image

Huh? Of course you can use regionprops. No need to use bwboundaries() at all, unless you just want to show the outlines of the segmented areas in the overlay above your original gray scale or color image.

If you want the area of all the white pixels in your binary image you can do it two ways, with slightly different results because they use different calculation methods

pixelSum1 = bwarea(binaryImage);
pixelSum2 = sum(binaryImage(:));

If you want the area of each blob in the image individually, you can do it like this:

labeledImage = bwlabel(binaryImage);
measurements = regionprops(labeledImage, 'Area');
allAreas = [measurements.Area];  % List of all the blob areas.
totalAreaOfAllBlobs = sum(allAreas); % Will be the same as pixelSum2

MATLAB: After calculating the centroid of an image, which value from the resulting structure is the result

regionprops assumes (with the syntax you have used) that your images are binary, with a number of disconnected regions of white pixels. The list of centroids xy1 and yz1 that you have formed are the centroids of these disconnected regions.

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MATLAB: Total area of a region of binary image

MATLAB: After calculating the centroid of an image, which value from the resulting structure is the result

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