Length of a thin curved object in an image
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I'd like to use image analysis to calculate the length of a thread.
Because the thread is not entirely straight, I can't just use regionprops, so I think the best option is to use the function bwdistgeodesic
In the bwdistgeodesic function, what is it expecting for the variable "mask"? How could I use image analysis to generate said mask? I've looked into using regionprops 'Extrema' property, but since I'm not sure what the "mask" variable is in bwdistgeodesic, I'm not sure how I would use the x,y dimensions from 'Extrema' in a mask.
I've attached the example image I'm using - with a "thread" and a one inch coin for size reference.
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Accepted Answer
Matt J
on 9 Jan 2018
Edited: Matt J
on 9 Jan 2018
Because the thread is not entirely straight, I can't just use regionprops,
Why not? Couldn't you just do
S=regionprops( bwareafilt(BW,1,'smallest') ,'Perimeter');
length=S.Perimeter/2
4 Comments
Matt J
on 9 Jan 2018
I think you could just extract the points using regionprops(...,'PixelList') and then apply filtering.
More Answers (1)
Image Analyst
on 9 Jan 2018
Assuming your line is just a one pixel thick line, you could just compute the area with bwarea() which weights the area depending on the shape of the boundary.
binaryImage = bwareafilt(binaryImage, 1, 'smallest'); % Extract smallest area.
% Now only the line is remaining.
lineLength = bwarea(binaryImage); % Get area, which is it's length.
2 Comments
Matt J
on 10 Jan 2018
If it's many pixels wide, you could try to thin it using,
BW = bwmorph(BW,'skel',Inf);
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