Erosion

Find local minima in binary or intensity image

• Library:

• Computer Vision Toolbox / Morphological Operations

• 

Description

The Erosion block slides a neighborhood or structuring element over an image, finds the local minima, and creates an output matrix from these minimum values. If the neighborhood or structuring element has a center element, the block places the minima there, as shown in this figure.

If the neighborhood or structuring element does not have an exact center, the block has a bias toward the upper-left of the central elements and places the minima there, as shown in this figure.

This block uses flat structuring elements only.

Ports

Input

I — Input image

matrix

Specify an input image as a matrix of binary or intensity values. This port is unnamed until you set the Neighborhood or structuring element source parameter to Input port.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point

Nhood — Neighborhood values

vector | matrix

Specify neighborhood values, representing a structuring element, as a vector or matrix of 1s and 0s.

Dependencies

To enable this port, set the Neighborhood or structuring element source parameter to Input port.

Data Types: Boolean

Output

Port_1 — Eroded image

matrix

Eroded image, returned as a matrix. The size and data type of the output image are the same as those of the input image.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean | fixed point

Parameters

Neighborhood or structuring element source — Source of neighborhood or structuring element

Specify via dialog (default) | Input port

Specify the source of the neighborhood or structuring element as one of these options:

• Specify via dialog — Use the Neighborhood or structuring element parameter to specify a neighborhood or structuring element.

• Input port — Use the Nhood input port to specify neighborhood values representing a structuring element.

Neighborhood or structuring element — Neighborhood or structuring element

strel('square',4) (default)

Specify the neighborhood or structuring element as a vector or matrix of 1s and 0s, a strel object, or an array of strel objects. When you specify an array of strel objects, the block applies each object to the entire image in sequence.

If the structuring element is decomposable into smaller elements, the block execution speed improves due to the more efficient algorithm.

Dependencies

To enable this parameter, set the Neighborhood or structuring element source parameter to Specify via dialog.

Model Examples

Boundary Extraction of Binary Image

Extract a boundary from a binary image.

Block Characteristics

Data Types	Boolean | double | fixed point | integer | single
Multidimensional Signals	no
Variable-Size Signals	yes

References

[1] Soille, Pierre. Morphological Image Analysis. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. https://doi.org/10.1007/978-3-662-05088-0.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.