bwmorph3

Morphological operations on binary volume

Syntax

J = bwmorph3(V,operation)

Description

J = bwmorph3(V,operation) applies a morphological operation to the binary volume V and returns the results of the operation in binary volume J.

Examples

Compare the Clean and Majority Operations

Load 3-D MRI volumetric data and create a binary volume. Use volshow to view the volumetric data with a gray color.

load mristack;
BW1 = mristack > 127;
cmap = [0.6 0.6 0.6];
volshow(BW1,Colormap=cmap);

To remove voxels that are set to 1 and that are also surrounded by voxels set to 0, perform the "clean" operation on the volumetric data. When determining which voxels to remove, the "clean" operation considers 26 neighboring voxels. Use volshow to view the results.

BW2 = bwmorph3(BW1,"clean");
volshow(BW2,Colormap=cmap);

For comparison, perform the "majority" operation on the volumetric data. The "majority" operation performs a similar task to the "clean" operation but only retains voxels if more than half (the majority) of the voxels in the neighborhood of the target voxel are set to 1. When determining which voxels to retain, the "majority" operation also considers 26 neighboring voxels. Use volshow to view the results.

BW3 = bwmorph3(BW1,"majority");
volshow(BW3,Colormap=cmap);

Input Arguments

V — Input volume

numeric array | logical array

Input volume, specified as a numeric or logical array. For numeric input, any nonzero pixels are considered to be 1 (true).

bwmorph3 accepts 1-D, 2-D, or 3-D arrays. If you specify 1-D or 2-D input arrays, then bwmorph3 performs the morphological operation as defined for a 3-D volume. If you want 2-D behavior, use bwmorph instead.

operation — Morphological operation to perform

character vector | string scalar

Morphological operation to perform, specified as one of the following character vectors or string scalar.

Operation	Description	Illustration Before and After Processing
"branchpoints"	Find branch points of skeleton. Branch points are the voxels at the junction where multiple branches meet. To find branch points, the image must be skeletonized. To create a skeletonized image, use bwskel.
"clean"	Remove isolated voxels, setting them to 0. An isolated voxel is an individual, 26-connected voxel that is set to 1 that are surrounded by voxels set to 0.
"endpoints"	Find end points of skeleton. End points are voxels at the ends of branches. Note: To find end points, the image must be skeletonized. To create a skeletonized image, use bwskel.
"fill"	Fill isolated interior voxels (holes), setting them to 1. Isolated interior voxels are individual voxels that are set to 0 that are surrounded (6-connected) by voxels set to 1.
"majority"	Keep a voxel set to 1 if 14 or more voxels (the majority) in its 3-by-3-by-3, 26-connected neighborhood are set to 1; otherwise, set the voxel to 0.
"remove"	Remove interior voxels, setting it to 0. Interior voxels are individual voxels that are set to 1 that are surrounded (6-connected) by voxels set to 1.

Data Types: char | string

Output Arguments

J — Volume after morphological operations

logical array

Volume after morphological operations, returned as a logical array of the same size as input volume V.

Tips

• To perform the morphological operations erosion or dilation on 3-D volumes, use the imerode or imdilate functions, specifying the structuring element ones(3,3,3).

• To perform morphological closing, opening, top-hat filtering, or bottom-hat filtering on 3-D volumes, use the imclose, imopen, imtophat, or imbothat functions, specifying the structuring element ones(3,3,3).

Extended Capabilities

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.

Version History

Introduced in R2018a

R2022b: Support for thread-based environments

bwmorph3 now supports thread-based environments.