Is there any way to check whether two pixels in a binary image are connected, if connected, it will return TRUE else FALSE.....???

Based on connectivity or whether two pixels in another image ( Image 1 ) are connected, I have to draw line between those pixels in another image (Image 2).? Remember Image 2 carries interest points (branch,end,start, and another important points) of image 1.Any suggestion..?

Answer 1

[Image Analyst]

If you simply want to see if they're connected, use bwlabel() to do connected component labelling on them, and then check for the same label value (meaning they're part of the same connected region):

[labeledImage, numberOfRegions] = bwlabel(binaryImage);
if labeledImage(row1, col1) == labeledImage(row2, col2)
    % They're connected.
end

Calling bwdistgeodesic() or regionprops() will give you the pixels connecting them.

bwdistgeodesic() will give you the shortest path. See Steve's blog: http://blogs.mathworks.com/steve/2011/11/01/exploring-shortest-paths-part-1/.

Whereas regionprops() (or find() after using ismember() to extract the region you want) will give you ALL the pixels in the region.

[Mohammad Bhat]

Sir, I got the desired coordinates to whom I have to now connect edges or form an Adjacency matrix..how can I do that...

[Mohammad Bhat]

A=kl_thin;      %  Skeletionised Image

B = rgb_final;  % key_points taken from skeleton Image

   [r,c]=find(B==1); % Finding coordinates of Key_points
   rc=[r,c]; 
  [labeledImage, numberOfRegions] = bwlabel(A);  % labeling pixels in skeletal 
                                                 %  Image i.e., in A  
k=1;
   for i=1:length(rc)
       for j=i+1:length(rc)
if labeledImage(rc(i,1), rc(i,2)) == labeledImage(rc(j,1), rc(j,2)) % checking their respective labels
h1=sub2ind(size(kl_thin),rc(i,1), rc(i,2));  % if connected extract respective Linear Indices
          h2=sub2ind(size(kl_thin),rc(j,1), rc(j,2));
          Edges(k,:)=[h1 h2]; % build a edge list
k=k+1;
    end
    end
 end

Now, Problem is When I am building Adjacency Matrix, I am not getting the desired graph that will connect each key_point (acts as nodes) when they are connected in skeletal Image i.e., In Image B. How to do achieve the desired graph...

Answer 2

[Walter Roberson]

https://www.mathworks.com/help/images/ref/bwdistgeodesic.html

You can use the (BW, R, C) form, where R and C are row and column of one of the two endpoints to be queried. Index the result of the function at the other endpoint. If the result there is infinity then there is no connection.

[Mohammad Bhat]

For example pixel 1 has coordinates are P1(10,20) and another pixel coordinates P2(50,60).How to check it from bwdistgeodesic(BW,C,R).....

[Walter Roberson]

D = bwdistgeodesic(BW, 10, 20);
if ~isinf( D(50,60) )
   they are connected
end

[Mohammad Bhat]

Sir, I have two images One is regular image as shown in figure and another processed form of same image, where I extracted intreset points (important points) I have to draw underlying graph using these important points. For each impportant point in image 2, I have to check whether there is an edge between these two in original image...from this logic it will show yes for any two points, by this I will get edges from all points to all points..

[Walter Roberson]

L = imclearborder(im2bw(imread('lllllll.jpg')));
H = imclearborder(im2bw(imread('hhhhh.jpg')));
Lpos = find(L);
HLab = bwlabel(H);
LLab = HLab(Lpos);
[LRow, LCol] = ind2sub(size(L), Lpos);

LLab is the same for all pixels that were originally part of the same component.

groups = accumarray(LLab, (1:length(LLab)).', [], @(x) {x});

now groups is a cell array of groupings. The values in any one groups{K} are indices into Lpos, the linear indices of the representative pixels in L. Perhaps you might prefer

groupsLidx = accumarray(LLab, Lpos, [], @(x) {x});

in which for any given groupsLidx{K} all of the members are linear indices of individual pixels.

Or perhaps,

LLimg = zeros(size(HLab));
LLimg(Lpos) = HLab(Lpos);

and now LLimg(R1, C1) and LLimg(R2, C2) are part of the same original component in H if they have the same value.

[Mohammad Bhat]

Sir ,I tried it but not working, need further help , here are my images, if possible kindly give me some

code:-

I have to connect each pair of nodes in image 2 , whenever they are directly connected in image 1 such

that Image 3 will result..

Answer 3

[Mohammad Bhat]

This is my image after I extracted important image from above original image...