Rvision (version 0.6.0)

connectedComponents: Find Connected Components in a binary Image

Description

connectedComponents computes the connected components (i.e. areas of contiguous non-zero pixels) of a binary image.

Usage

connectedComponents(
  image,
  connectivity = 8,
  algorithm = "grana",
  table = TRUE,
  target = "new"
)

Arguments

image

An an 8-bit (8U) single-channel Image object.

connectivity

The connetivity neighborhood to decide whether 2 pixels are contiguous. This parameter can take two values:

• 4: the neighborhood of a pixel are the four pixels located above (north), below (south), to the left (west) and right (east) of the pixel.

• 8 (the default): the neighborhood of a pixel includes the four 4-neighbors and the four pixels along the diagonal directions (northeast, northwest, southeast, and southwest).

algorithm

A character string specifying the connected components labeling algorithm to use. This parameter can take two values:

• "grana" (the default): Block-based connected-component labeling for 8-way connectivity, scan array union find labeling for 4-way connectivity.

• "wu": Scan array union find labeling for both 8-way and 4-way connectivity.

table

A boolean indicatinng whether the coordinates of the pixels of each component should be returned.

target

The location where the results should be stored. It can take 2 values:

• "new":a new Image object is created and the results are stored inside (the default).

• An Image object:the results are stored in another existing Image object. In this case, target must be a single channel image with a 16U or 32S bit depth. Note that this will replace the content of target.

Value

A list with 1 to 3 items:

• n: the number of connected components in the image. It is always returned.

• table: if table=TRUE, a matrix with 3 columns representing the identity of the connected components (id), and the x-y coordinates of the pixels they are composed of.

• labels: if target="new" a 32S single-channel image in which each pixel of each connected component is represented by the identity number of the component, and the background pixels by zero.

See Also

Image

Examples

# NOT RUN {
dots <- image(system.file("sample_img/dots.jpg", package = "Rvision"))
dots_gray <- changeColorSpace(dots, "GRAY")
dots_bin <- dots_gray < 200
cc <- connectedComponents(dots_bin)

# }