Connectivity

Connectivity between pixels is an important concept in digital image processing and is used for establishing boundaries of labeled objects and components. Labeled pixels are said to be connected if they are adjacent to each other or if their gray level satisfies a specified criterion of similarity, such as an equal intensity level. You should note that a set of pixels that are connected to each other is often called a connected component.

Connectivity is selectable in Dragonfly for creating multi-ROIs from regions of interest with the 'connected components' options, painting with the Point & Click tools, and for refining regions of interest by processing islands.

4-Connected and 8-Connected

When working with 2D images or on single slices of 3D images, 4-connected and 8-connected are used to establish connectivity.

4-connected versus 8-connected

4-connected… Propagation is done by strictly using the 4 faces adjacent to the current seed and will result in the maximum number of connected components.

8-connected… Propagation is done in all directions using the 4 faces and 4 corners adjacent to the current seed and will result in the fewest connected components.

6-Connected and 26-Connected

When working with 3D images, 6-connected and 26-connected are used to establish connectivity.

6-connected versus 26-connected

6-connected… Propagation is done by strictly using the 6 faces adjacent to the current seed and will result in the maximum number of connected components.

26-connected… Propagation is done in all directions, using the 6 faces, 12 edges, and 8 corners adjacent to the current seed. Will result in the fewest connected components, but computation times may increase.