Dilation

Dilate binary or intensity image by finding local maxima

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库:
电脑Vision Toolbox / Morphological Operations

Description

TheDilationblock performs morphological dilation on an intensity or binary image and outputs the dilated image.

To define the structuring element that the block applies to the image, use theNeighborhood or structuring elementparameter.

This block uses two-dimensional flat structuring elements only.

Ports

Input

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`I`— Input image
matrix

Specify an input image as a matrix of intensity values. This port is unnamed unless you set theNeighborhood or structuring element sourceparameter toInput port.

`Nhood`— Neighborhood values
vector | matrix

Specify neighborhood values representing a structuring element as a vector or matrix of1s and0s or by using thestrelfunction.

Dependencies

To enable this port, set theNeighborhood or structuring element sourceparameter toInput port.

Data Types:Boolean

Output

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`Port_1`— Dilated image
matrix

The block returns the dilated image as a matrix of intensity values. The size and data type of the output image are the same as those of the input image.

Parameters

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`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 theNeighborhood or structuring elementparameter to specify a neighborhood or structuring element.
Input port— Use theNhoodinput port to specify neighborhood values representing a structuring element.

`Neighborhood or structuring element`— Neighborhood or structuring element
`[1 1; 1 1]`(default) | vector | matrix

Specify a neighborhood or structuring element as a vector or matrix of1s and0s, astrelobject, or an array ofstrelobjects. When you specify an array ofstrelobjects, the block applies each object to the entire image sequentially.

If the structuring element is decomposable into smaller elements, the block uses a more efficient algorithm that can execute more quickly.

Dependencies

To enable this parameter, set theNeighborhood or structuring element sourceparameter, toSpecify via dialog.

Model Examples

Dilation of Binary Image

Increase the size of a binary image object and fill holes in it.

Open Script

Block Characteristics

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

More About

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Dilation and Structuring Element

Performing dilation on an image includes:

Increasing the size of the object by expanding the image pixels and adding pixels to the boundary of the object.
Filling small holes and broken areas
Connecting areas separated by a space smaller than the structuring element

The direction and extent of the growth of an object in an image depends on the shape of the structuring element. Each structuring element has an origin.

If the structuring element is symmetrical, the origin coincides with its centroid.
If the structuring element is asymmetrical, the pixel in the structuring element that is close to its centroid and is in the top-left direction is considered as the origin.

TheDilationblock rotates the structuring element about this origin and places the origin over each pixel of the image object. The block creates the dilated image from the local maxima values at each pixel.

Binary Dilation

The binary dilation ofAbyB, denoted asA⨁B, is defined as the set operation:

$A \oplus B = {z | {(\hat{B})}_{z} \cap A \neq \emptyset},$

where $\hat{B}$ is the reflection of the structuring elementB. Note that some applications use a definition of dilation in which the structuring element is not reflected.

Grayscale Dilation

In the general form of grayscale dilation, the structuring element has a specified height. The grayscale dilation ofA(x,y) byB(x,y)是维efined as:

$(A \oplus B) (x, y) = 马克斯 {A (x - x^{'}, y - y^{'}) + B (x^{'}, y^{'}) | (x^{'}, y^{'}) \in D_{B}},$

whereD_Bis the domain of the structuring elementBandA(x,y)is assumed to be–∞outside the domain of the image. To create a structuring element with nonzero height values, use the syntaxstrel(nhood,height), whereheightspecifies the height values andnhoodcorresponds to the structuring element domainD_B.

Grayscale dilation is often performed with a flat structuring element(B(x,y) = 0). Grayscale dilation using such a structuring element is equivalent to a local-maximum operator:

$(A \oplus B) (x, y) = 马克斯 {A (x - x^{'}, y - y^{'}) | (x^{'}, y^{'}) \in D_{B}} .$

All of thestrelsyntaxes except forstrel(nhood,height),strel("arbitrary",nhood,height), andstrel("ball",...)produce flat structuring elements.

References

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

[2] Gonzalez, Rafael C., Richard E. Woods, and Steven L. Eddins.Digital Image Processing Using MATLAB. Third edition. Knoxville: Gatesmark Publishing, 2020.

Extended Capabilities

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

版本历史

Introduced before R2006a

Dilation

Description