find_components

finds the connected components of an image

Description

find_components finds the connected components of an image. Two pixels are in the same component if they are adjacent (north, south, east, or west, but not NW, SW, etc) and have the same value.

This was a bit of recreational weekend programming, in reply to Doug Hull's Puzzler of Aug. 18, 2008:

http://blogs.mathworks.com/pick/2008/08/18/puzzler-find-largest-connected-island/

It also serves as a nice example of DMPERM. To read more about dmperm, and to read its code, see CSparse or CXSparse on the File Exchange.

• Acknowledgements: This submission has inspired the following:; ISLANDS
• MATLAB release: MATLAB 7.6 (R2008a)
• Other requirements: Your results will vary if you use MATLAB 7.4 or earlier; DMPERM was upgraded for MATLAB 7.5.
• Other Files: find_components/Contents.m, ; find_components/find_components.m, ; find_components/find_components.png, ; find_components/find_components_example.m, ; find_components/largest_component.m

[M P]

 

[John D'Errico]

Professionally written. Excellent help. Internal comments that can teach everyone on the FEX something about how to write code.

[Kenneth Eaton]

I hadn't ever happened upon DMPERM before. Thanks for pointing out something new, Tim.

[Ben Petschel]

Nice code Tim. I hadn't come across DMPERM before either.

The variables K, East, South aren't really needed because K(E)=E, K(S)=S, East(E)=E+m, South(S)=S+1, and E & S can be defined without K.

[Thomas Clark]

Thanks Tim!

This is very popular in the current ML contest (flooding a matrix with colour, Fall 2009).