Label
Label connected components in binary image
Libraries:
Computer Vision Toolbox /
Morphological Operations
Description
The Label block finds and labels the connected components or objects in a 2-D binary image. The block ignores the background pixels in the input image and searches for connected components within remaining pixels. The block then labels all the pixels of each connected component with a unique number and computes the number of labeled objects.
Examples
Ports
Input
BW — Input binary image
vector | matrix
The input image must be a vector or matrix of binary values, each element
representing a pixel of the image. The block categorizes pixels with a value of
0
as background pixels, searching for connected components within
pixels with a value of 1
.
Data Types: Boolean
Output
Label — Labeled objects
vector | matrix
Labeled objects in the input image, returned as a vector or matrix of nonnegative
integers. The elements of the output vector or matrix labeled 0
represent the background, the elements labeled 1
represent the
first object, the elements labeled 2
represent the second object,
and so on. The size of this output matches the size of the BW
input.
Dependencies
To enable this port, set the Output parameter to either
Label matrix
or Label matrix and number of
labels
.
Data Types: uint8
| uint16
| uint32
Count — Number of labeled objects
scalar
Number of labeled objects, returned as a scalar.
Dependencies
To enable this port, set the Output parameter to either
Number of labels
or Label matrix and
number of labels
.
Data Types: uint8
| uint16
| uint32
Parameters
Connectivity — Type of pixel connectivity
8
(default) | 4
Specify how the block defines which pixels are connected to each other. If you want
to connect adjacent pixels in only the horizontal and vertical directions, select
4
. If you want to connect adjacent pixels in the horizontal,
vertical, and diagonal directions, select 8
. These figures show how
the block defines a connected component for 4-connected and 8-connected pixels. The
block considers the white pixels marked by black circles to be connected to each other.
Type of Connectivity | Connected Pixels |
---|---|
4-connected pixels |
|
8-connected pixels |
|
Output — Block output
Label matrix and number of labels
(default) | Label matrix
| Number of labels
Specify the block output as one of these options:
Label matrix
— The block outputs the labeled objects at the Label port.Number of labels
— The block outputs the number of labeled objects at the Count port.Label matrix and number of labels
— The block outputs both the labeled objects and number of labeled objects to the Label and Count ports, respectively.
Output data type — Data type of output
Automatic
(default) | uint8
| uint16
| uint32
Specify the data type of the outputs at the Label and
Count ports. When you specify this parameter as
Automatic
, the block calculates the maximum number of
objects that can fit inside the image based on the image size and the specified
connectivity. Using this calculation, it chooses the output data type with the minimum
value that guarantees unique region labels.
If label exceeds data type size, mark remaining regions using — Overflow mode of output labels
maximum value of the output data
type
(default) | zero
Use this parameter to specify the behavior of the block when the block finds more objects than the maximum possible value the output data type can represent. The block labels the remaining objects with the value determined by one of these options:
maximum value of the output data type
— The block labels the remaining objects with the maximum value of the output data type.zero
— The block labels the remaining objects with0
.
Dependencies
To enable this parameter, set the Output data type parameter
to either uint8
or
uint16
.
Block Characteristics
Data Types |
|
Multidimensional Signals |
|
Variable-Size Signals |
|
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.
Version History
Introduced before R2006a
See Also
Blocks
- Dilation | Erosion | Opening | Closing | Blob Analysis
Functions
bwconncomp
|bwselect
|regionprops
|bwlabel
|bwlabeln
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