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How to find the midpoint between two curves in an image

5 vues (au cours des 30 derniers jours)
Suraj Sudhakar
Suraj Sudhakar le 27 Juil 2022
Commenté : Suraj Sudhakar le 10 Août 2022
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

Réponse acceptée

Akira Agata
Akira Agata le 7 Août 2022
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)
  3 commentaires
yanqi liu
yanqi liu le 9 Août 2022
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)
Suraj Sudhakar
Suraj Sudhakar le 10 Août 2022
That works, thanks

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