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

Asked by Hernán Madrid Oyarzún on 11 Nov 2019 at 14:43
Latest activity Commented on by Hernán Madrid Oyarzún on 25 Nov 2019 at 23:47
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!!
CON REMOVE.png
the "1.png" image can be downloaded from the link.
clc
clear all
a=imread('1.png');
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

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1 Answer

Answer by Matt J
on 11 Nov 2019 at 16:36
Edited by Matt J
on 11 Nov 2019 at 18:51
 Accepted Answer

load River
C=watershed(bwdist(A))==0;
[icoords,jcoords]=find(C); %coordinates of center line
imshow(A+C)

  3 Comments

Great approach!
Where did A come from?
It's just a cropping of the image in the original post.
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.

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