CODEWITHSUNDEEP
c++opencvimage-processingcomputer-visionconnected-components
user7209199
user7209199

Reputation: 59

Connected Component Labeling

In OpenCV 3.0 there is a function called connectedComponent.

I know that it takes as input a binary image and returns the labels and the number of connected components, but what algorithm is used internally?

Upvotes: 1

Views: 3021

Answers (2)

Miki
Miki

Reputation: 41765

OpenCV is open source. You can look at the documentation and the source code.

You can choose 2 algorithms to perform connected component lablelling:

The default in OpenCV >= 3.2 (CCL_DEFAULT) uses Wu's algorithm for 4-connectivity, and Grana's algorithm for 8 connectivity.

In OpenCV 3.0.0 you use Wu's algorithm for both 4 and 8 connectivity, while in OpenCV >= 3.2 you can choose one of the 3 options, according to the fields connectivity and ccltype:

       \  connectivity   4    |   8
        \                     |
type     \                    |
                              |
CCL_DEFAULT              Wu   |  Grana
CCL_WU                   Wu   |  Wu
CCL_GRANA                Wu   |  Grana

Upvotes: 7

MBo
MBo

Reputation: 80197

You can read about connected component labeling algorithms in numerous sources

OpenCV implementation is here and contains this clue:

 //Based on "Two Strategies to Speed up Connected Components Algorithms", 
 //the SAUF (Scan array union find) variant
 //using decision trees
 //Kesheng Wu, et al

Article

Upvotes: 1

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