How to find the midpoint between two curves in an image

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Suraj Sudhakar
Suraj Sudhakar 2022-7-27
评论： Suraj Sudhakar 2022-8-10
I have attached the image of the curve, I would like to extract the midpoint between the curve. (Ideally, the thickness of the given curve is constant). I tried extracting the gradient direction and using the line along the gradient direction to extract the midpoint, but the gradient direction is not perfectly tangential due to the discrete nature of the iimage
for (points in the upper line)
%get the gradient
gx=(bw(i+1,j)-bw(i-1,j))/2;
gy=(bw(i,j+1)-bw(i,j-1))/2;
theta=atan(gy/gx);
m = sin(theta); %slope of the line
%use the slope and known initial point (and assumption that thickness is constant to get a midpoint)
%issue is gradient can only take a few directions, hence getting wrong results
Wanted to know if there is any better way of doing this

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采纳的回答

Akira Agata
Akira Agata 2022-8-7
Ran in:
How abou the following?
% Load image
I = imread('https://jp.mathworks.com/matlabcentral/answers/uploaded_files/1079075/curve.PNG');
% Binarize the image
I = rgb2gray(I);
BW = imbinarize(I);
% Apply bwdist
J = bwdist(~BW);
% Find maximum position for each row
[~, pt] = max(J, [], 2);
% Create the output image
pt_ind = sub2ind(size(BW), 1:size(BW, 1), pt');
BW2 = false(size(BW));
BW2(pt_ind) = true;
% Let's check!
figure
imshowpair(BW, BW2)
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yanqi liu
yanqi liu 2022-8-9
yes，sir，if we make to U shape，may be just use
I = imread('curve2.png');
I = rgb2gray(I);
BW = imbinarize(I);
J = bwdist(~BW);
BW2 = J>max(J(:))*0.8;
figure
imshowpair(BW, BW2)

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