# How to find the midpoint between two curves in an image

5 vues (au cours des 30 derniers jours)
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)
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
##### 0 commentairesAfficher -2 commentaires plus anciensMasquer -2 commentaires plus anciens

Connectez-vous pour commenter.

### Réponse acceptée

Akira Agata le 7 Août 2022
How abou the following?
% 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 commentairesAfficher 1 commentaire plus ancienMasquer 1 commentaire plus ancien
yanqi liu le 9 Août 2022
yes，sir，if we make to U shape，may be just use
I = rgb2gray(I);
BW = imbinarize(I);
J = bwdist(~BW);
BW2 = J>max(J(:))*0.8;
figure
imshowpair(BW, BW2)
Suraj Sudhakar le 10 Août 2022
That works, thanks

Connectez-vous pour commenter.

### Catégories

En savoir plus sur Image Segmentation and Analysis dans Help Center et File Exchange

R2021a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by