imopen

Morphologically open image

Syntax

J = imopen(I,SE)

J = imopen(I,nhood)

Description

J = imopen(I,SE) performs morphological opening on the grayscale or binary image I using the structuring element SE. The morphological opening operation is an erosion followed by a dilation, using the same structuring element for both operations.

J = imopen(I,nhood) opens the image I, where nhood is a matrix of 0s and 1s that specifies the structuring element neighborhood.

This syntax is equivalent to imopen(I,strel(nhood)).

Examples

Morphologically Open Image with a Disk-Shaped Structuring Element

Read the image into the workspace and display it.

original = imread('snowflakes.png');
imshow(original);

Create a disk-shaped structuring element with a radius of 5 pixels.

se = strel('disk',5);

Remove snowflakes having a radius less than 5 pixels by opening it with the disk-shaped structuring element.

afterOpening = imopen(original,se);
figure
imshow(afterOpening,[]);

Input Arguments

I — Input image

grayscale image | binary image

Input image, specified as a grayscale image or binary image of any dimension.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | logical

SE — Structuring element

strel object | offsetstrel object

Structuring element, specified as a strel object or offsetstrel object. If the image I is of data type logical, the structuring element must be flat.

nhood — Structuring element neighborhood

matrix of 0s and 1s

Structuring element neighborhood, specified as a matrix of 0s and 1s.

Example: [0 1 0; 1 1 1; 0 1 0]

Output Arguments

J — Opened image

grayscale image | binary image

Opened image, returned as a grayscale image or binary image. J has the same data type as input image I.

Tips

• If the dimensionality of the image I is greater than the dimensionality of the structuring element, then the imopen function applies the same morphological opening to all planes along the higher dimensions.

  You can use this behavior to perform morphological opening on RGB images. Specify a 2-D structuring element for RGB images to operate on each color channel separately.

• When you specify a structuring element neighborhood, imopen determines the center element of nhood by floor((size(nhood)+1)/2).

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• imopen supports the generation of C code (requires MATLAB^® Coder™). Note that if you choose the generic MATLAB Host Computer target platform, imopen generates code that uses a precompiled, platform-specific shared library. Use of a shared library preserves performance optimizations but limits the target platforms for which code can be generated. For more information, see Types of Code Generation Support in Image Processing Toolbox.

• The input image I must be 2-D or 3-D.

GPU Code Generation

Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

Usage notes and limitations:

• The input image I must be 2-D or 3-D.

Thread-Based Environment

Run code in the background using MATLAB® backgroundPool or accelerate code with Parallel Computing Toolbox™ ThreadPool.

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays

Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

Usage notes and limitations:

• gpuArray input must be of type uint8 or logical.

• The structuring element SE must be flat and 2-D.

For more information, see Image Processing on a GPU.

Version History

Introduced before R2006a

R2022b: Support for thread-based environments

imopen now supports thread-based environments.