How to obtain an average polygon out of multiple polygon boundaries?

Hi, How do I obtain an average ROI from multiple ROIs drawn on different images? Thank you very much for your help.

Images=dir("*ExampleImage.tif");
S_Boundaries=[];
for i=1 :numel(Images)
    Image=imread(Images(i).name);
    imshow(Image); 
    p=drawpolygon();
    S_boundary{i}=p.Position
    S_Boundaries=[S_Boundaries; S_boundary{i}]
end
AverageBoundary = HelpFunction(S_Boundaries) 

%HelpFunction would compute an average boundary from multiple boundaries saved as S_Boundaries.

[Matt J]

Do you have a definition for "average boundary"?

[Sudip Paudel]

• Hi Matt, the average boundary meaning the one that represents the entire set of boundaries (I think a best fit boundary would work). Thank you.

Answer 1

[Image Analyst]

I already did this for someone else. Luckily I saved the code. It's attached.

[Sudip Paudel]

Hi Image Analyst, Thank you very much. It looks like the boundaries need to covert into BW images, is that right?

[Image Analyst]

Not really. You'll notice that I never computed boundary coordinates. I just used the cropped image, and that was already gray scale. If you had an RGB image you should convert it to grayscale so the shapes can be added together. To get the average shape, we don't need or want any color.

[Sudip Paudel]

Thank you for your comment. I have to draw the ROI/polygon manually though. I see you have used croppedBlob = props(k).Image; but I have only the boundaries.

[Image Analyst]

You can convert your polygons/boundaries into images with the poly2mask() function.

[Sudip Paudel]

Oh OK, thank you very much.