Comments on: Connected component labeling - Part 5 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/ Steve Eddins manages the Image & Geospatial development team at <a href="http://www.mathworks.com/">The MathWorks</a> and coauthored <a href="http://www.mathworks.com/support/books/book5291.html?category=-1&language=-1">Digital Image Processing Using MATLAB</a>. He writes here about image processing concepts, algorithm implementations, and MATLAB.<br><br><img> Sun, 08 Nov 2009 04:49:39 +0000 http://wordpress.org/?v=2.3.1 By: Steve http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20997 Steve Fri, 22 Aug 2008 13:25:03 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20997 DP—There are one or two <a href="http://www.mathworks.com/products/image/demos.html" rel="nofollow">Image Processing Toolbox product demos</a> that might be helpful. DP—There are one or two Image Processing Toolbox product demos that might be helpful.

]]> By: DP http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20996 DP Fri, 22 Aug 2008 13:18:01 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20996 Hi Steve: i am happy to saw that your update on "Image visualization using transparency" to label the two connected objects as a single object. However, i am having a problem with seperating two overlap object to seperate. in binary image i am trying to seperate two/three overlap rectangular object to seperate them and calculate the centroids of each seperated object. could you please show me one example? Thank you. Sincerely, DP Hi Steve:
i am happy to saw that your update on “Image visualization using transparency” to label the two connected objects as a single object.
However, i am having a problem with seperating two overlap object to seperate. in binary image i am trying to seperate two/three overlap rectangular object to seperate them and calculate the centroids of each seperated object. could you please show me one example?

Thank you.
Sincerely,
DP

]]> By: Steve http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20993 Steve Fri, 22 Aug 2008 13:12:29 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20993 Nawal—You can the convex hull of each connected component via <tt>regionprops</tt>. Then you need a routine to determine if two polygons overlap. You don't a routine that works for general polygons, because the convex hull polygons will be, well, convex. :-) You might try searching the MATLAB Central File Exchange in addition to Google. Nawal—You can the convex hull of each connected component via regionprops. Then you need a routine to determine if two polygons overlap. You don’t a routine that works for general polygons, because the convex hull polygons will be, well, convex. :-) You might try searching the MATLAB Central File Exchange in addition to Google.

]]> By: Nawal http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20988 Nawal Thu, 21 Aug 2008 23:52:53 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20988 Thank you Steve. Sorry, in my case there is an overlap between bounding box of connected component not in connected component it self. I read today in some research paper the follwing idea we can use convex hull of connected component. where if there are an overlaping between two convex hull there are an overlap between bounding box of component. Thank you Steve.

Sorry, in my case there is an overlap between bounding box of connected component not in connected component it self. I read today in some research paper the follwing idea we can use convex hull of connected component. where if there are an overlaping between two convex hull there are an overlap between bounding box of component.

]]> By: Steve http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20987 Steve Thu, 21 Aug 2008 17:22:26 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20987 Nawal—You can't have two connected components that are overlapping. "Overlapping" indicates that you really only have one connected component. Nawal—You can’t have two connected components that are overlapping. “Overlapping” indicates that you really only have one connected component.

]]> By: Nawal http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20985 Nawal Thu, 21 Aug 2008 15:05:55 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20985 hi steve. How we can detect an overlaping between connected cmponent. can you help me. Thanks in advance Nawal hi steve.
How we can detect an overlaping between connected cmponent.
can you help me.

Thanks in advance
Nawal

]]> By: Steve http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20876 Steve Tue, 15 Jul 2008 16:54:04 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20876 Karthik—You didn't check your A matrix. This line: <pre> A(1:5+1:end) = 1; </pre> doesn't do what you thought it would. See <a href="http://blogs.mathworks.com/steve/2007/03/20/connected-component-labeling-part-3/#comment-6814" rel="nofollow">this comment</a> from Tim Davis about efficiently putting 1s on the diagonal of a sparse matrix. Karthik—You didn’t check your A matrix. This line:

A(1:5+1:end) = 1;

doesn’t do what you thought it would.

See this comment from Tim Davis about efficiently putting 1s on the diagonal of a sparse matrix.

]]> By: Karthik http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20875 Karthik Tue, 15 Jul 2008 16:23:54 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20875 Hi Steve, i have a problem in using dmperm function, as my adjacency pairs are not incremental. ie. example in below case i dont have label 4, as it forms a individual un-connected cluster. pairs = [ 2 3; 3 2; 1 2; 2 1; 5 6; 6 5]; here i have 5 nodes in total (ie. 1,2,3,5,6) A = sparse(pairs(:,1), pairs(:,2), 1); A(1:5+1:end) = 1; [p, q, r, s] = dmperm(A); this does not give correct result. how to solve this problem? Hi Steve, i have a problem in using dmperm function, as my adjacency pairs are not incremental. ie. example in below case i dont have label 4, as it forms a individual un-connected cluster.

pairs = [ 2 3; 3 2; 1 2; 2 1; 5 6; 6 5];

here i have 5 nodes in total (ie. 1,2,3,5,6)

A = sparse(pairs(:,1), pairs(:,2), 1);
A(1:5+1:end) = 1;

[p, q, r, s] = dmperm(A);

this does not give correct result. how to solve this problem?

]]> By: Edgar http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20829 Edgar Mon, 30 Jun 2008 11:20:35 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20829 Thanks Steve, in fact, I have done it using bwlabel but tweaking the parameters of the edge function a bit. Thanks Steve, in fact, I have done it using bwlabel but tweaking the parameters of the edge function a bit.

]]> By: Steve http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20821 Steve Wed, 25 Jun 2008 18:24:58 +0000 http://blogs.mathworks.com/steve/2007/05/11/connected-component-labeling-part-5/#comment-20821 Edgar—The function <tt>bwlabel</tt> computes the connected the components of your binary image. That's a well-defined operation - it's either being computed correctly or it isn't. So can you elaborate on what you mean by saying the result is not "good"? Edgar—The function bwlabel computes the connected the components of your binary image. That’s a well-defined operation - it’s either being computed correctly or it isn’t. So can you elaborate on what you mean by saying the result is not “good”?

]]>