# how can I find the coordinates of the central axis of a river in an image (binary)?

2 views (last 30 days)
I am trying to find a vector that contains the midpoint or talweg of an image of the Valdivia River (Chile) To do this I am using a code that I found on this page, I attached it. The problem is that with the example there is no problem, but when changing to my image I get an error. help!! clc
clear all
imshow(a);
impixelinfo
b=im2bw(a);
figure,imshow(b)
imfinfo('1.png')
impixelinfo
E = edge(b);
figure;imshow(E)
c=imcomplement(E);
figure,imshow(c)
impixelinfo
[col row]=size(c);
k=1;
count=1;
for i=1:col
for j=1:row
if c(i,j)==0
[j i]
if i==i
z(k)=j
k=k+1;
g=i;
end
count=count+1;
end
end
k=1;
if (z(2)-z(1))>2
av=(z(1)+z(2))/2;
hold on
plot(av,g,'.')
else
av=(z(1)+z(3))/2;
hold on
plot(av,g,'.k')
end
end

Matt J on 11 Nov 2019
Edited: Matt J on 11 Nov 2019
C=watershed(bwdist(A))==0;
[icoords,jcoords]=find(C); %coordinates of center line
imshow(A+C) Adam Danz on 11 Nov 2019
Great approach!
Where did A come from?
Matt J on 11 Nov 2019
It's just a cropping of the image in the original post.
Hernán Madrid Oyarzún on 25 Nov 2019
thanks, works perfectly and it´s very simple,
Now i´m trying to find the coordinates of the north or south banks to can find the width of every point of the line detected by this process. if you can help me I would appreciate it a lot.