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Erosion

Find local minima in binary or intensity image

  • Library:
  • Computer Vision Toolbox / Morphological Operations

  • Erosion block

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.

Three-by-three grid with "X" over center square, representing local minima.

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.

Four-by-four grid with "X" over the square in the second column of the second row, representing local minima.

This block uses flat structuring elements only.

Ports

Input

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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

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

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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

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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.

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.

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™.

See Also

Blocks

Functions

Objects

Introduced before R2006a