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

Question

Hernán Madrid Oyarzún 2019-11-11

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/490446-how-can-i-find-the-coordinates-of-the-central-axis-of-a-river-in-an-image-binary

评论： Hernán Madrid Oyarzún 2019-11-25

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!!

https://la.mathworks.com/matlabcentral/fileexchange/66779-algorithm-for-finding-the-center-of-a-river-of-an-image?s_tid=srchtitle

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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Answer 1

Matt J 2019-11-11

4
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/490446-how-can-i-find-the-coordinates-of-the-central-axis-of-a-river-in-an-image-binary#answer_400940

编辑：Matt J 2019-11-11

在 MATLAB Online 中打开

River.mat

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

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Matt J 2019-11-11

It's just a cropping of the image in the original post.

Hernán Madrid Oyarzún 2019-11-25

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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