regionprops3
Measure properties of 3-D volumetric image regions
Syntax
Description
measures a set of properties for each connected component (object) in the 3-D
volumetric binary image stats
= regionprops3(BW
,properties
)BW
. The output
stats
denotes different properties for each object.
regionprops3
finds unique objects in volumetric binary images
using 26-connected neighborhoods. For more information, see Pixel Connectivity. To find objects
using other types of connectivity, instead use bwconncomp
to create the connected
components, and then pass the result to regionprops3
using the
CC
argument.
For all syntaxes, you can omit the properties
argument. In
this case, regionprops3
returns the
"Volume"
, "Centroid"
, and
"BoundingBox"
measurements.
measures a set of properties for each connected component (object) in
stats
= regionprops3(CC
,properties
)CC
, which is a structure returned by bwconncomp
.
measures a set of properties for each labeled region in the 3-D label image
stats
= regionprops3(L
,properties
)L
.
Examples
Estimate Centers and Radii of Objects in 3-D Volumetric Image
Create a binary image with two spheres.
[x,y,z] = meshgrid(1:50,1:50,1:50); bw1 = sqrt((x-10).^2 + (y-15).^2 + (z-35).^2) < 5; bw2 = sqrt((x-20).^2 + (y-30).^2 + (z-15).^2) < 10; bw = bw1 | bw2;
Get the centers and radii of the two spheres.
s = regionprops3(bw,"Centroid","PrincipalAxisLength"); centers = s.Centroid
centers = 2×3
20 30 15
10 15 35
diameters = mean(s.PrincipalAxisLength,2)
diameters = 2×1
19.9641
9.8241
radii = diameters/2
radii = 2×1
9.9820
4.9120
Get All Statistics for Cube Within a Cube
Make a 9-by-9 cube of 0s that contains a 3-by-3 cube of 1s at its center.
innercube = ones(3,3,3);
cube_in_cube = padarray(innercube,[3 3],0,'both');
Get all statistics on the cube within the cube.
stats = regionprops3(cube_in_cube,'all')
stats=1×18 table
Volume Centroid BoundingBox SubarrayIdx Image EquivDiameter Extent VoxelIdxList VoxelList PrincipalAxisLength Orientation EigenVectors EigenValues ConvexHull ConvexImage ConvexVolume Solidity SurfaceArea
______ ___________ ______________________________________ ___________________________________ _______________ _____________ ______ _____________ _____________ _______________________ ___________ ____________ ____________ _____________ _______________ ____________ ________ ___________
27 5 5 2 3.5 3.5 0.5 3 3 3 {[4 5 6]} {[4 5 6]} {[1 2 3]} {3x3x3 logical} 3.7221 1 {27x1 double} {27x3 double} 3.873 3.873 3.873 0 0 0 {3x3 double} {3x1 double} {24x3 double} {3x3x3 logical} 27 1 41.07
Input Arguments
BW
— Volumetric binary image
3-D logical array
Volumetric binary image, specified as a 3-D logical array.
regionprops3
sorts the objects in the volumetric
binary image from left to right based on the top-left
extremum of each component. When multiple objects have the same horizontal
position, the function then sorts those objects from top to bottom, and
again along the third dimension. regionprop3
returns
the measured properties, stats
, in the same order as
the sorted objects.
Data Types: logical
CC
— Connected components
structure
Connected components of a 3-D volumetric image, specified as a structure
returned by bwconncomp
using a 3-D
connectivity value, such as 6, 18, or 26. CC.ImageSize
must be a 1-by-3 vector.
Data Types: struct
L
— Label image
3-D numeric array | 3-D categorical array
Label image, specified as one of the following.
A 3-D numeric array. Voxels labeled
0
are the background. Voxels labeled1
make up one object; voxels labeled2
make up a second object; and so on.regionprops3
treats negative-valued voxels as background and rounds down input voxels that are not integers. You can get a numeric label image from labeling functions such aswatershed
orlabelmatrix
.A 3-D categorical array. Each category corresponds to a different region.
Data Types: single
| double
| int8
| int16
| int32
| uint8
| uint16
| uint32
| categorical
properties
— Type of measurement
"basic"
(default) | comma-separated list of strings or character vectors | cell array of strings or character vectors | "all"
Type of measurement, specified as a comma-separated list of strings or
character vectors, a cell array of strings or character vectors,
"all"
or "basic"
.
If you specify
"all"
, thenregionprops3
computes all the shape measurements. If you also specify a grayscale image, thenregionprops3
returns all of the voxel value measurements.If you specify
"basic"
or do not specify theproperties
argument, thenregionprops3
computes only the"Volume"
,"Centroid"
, and"BoundingBox"
measurements.
The following table lists all the properties that provide shape measurements. The Voxel Value Measurements table lists additional properties that are valid only when you specify a grayscale image.
Shape Measurements
Property Name | Description | Code Generation |
---|---|---|
"BoundingBox" | Smallest cuboid containing the region, returned as a
1-by-6 vector of the form [ulf_x ulf_y ulf_z
width_x width_y width_z] .
ulf_x , ulf_y , and
ulf_z specify the upper-left front
corner of the cuboid. width_x ,
width_y , and
width_z specify the width of the
cuboid along each dimension. | Yes |
"Centroid" | Center of mass of the region, returned as a 1-by-3 vector. The three elements specify the (x, y, z) coordinates of the center of mass. | Yes |
"ConvexHull" | Smallest convex polygon that can contain the region, returned as a p-by-3 matrix. Each row of the matrix contains the x-, y-, and z-coordinates of one vertex of the polygon. | No |
"ConvexImage" | Image of the convex hull, returned as a volumetric binary
image with all voxels within the hull filled in (set to
on ). The image is the size of the
bounding box of the region. | No |
"ConvexVolume" | Number of voxels in ConvexImage ,
returned as a scalar. | No |
"EigenValues" | Eigenvalues of the voxels representing a region, returned
as a 3-by-1 vector. regionprops3 uses
the eigenvalues to calculate the principal axes
lengths. | Yes |
"EigenVectors" | Eigenvectors of the voxels representing a region,
returned as a 3-by-3 vector.
regionprops3 uses the eigenvectors
to calculate the orientation of the ellipsoid that has the
same normalized second central moments as the
region. | Yes |
"EquivDiameter" | Diameter of a sphere with the same volume as the region,
returned as a scalar. Computed as
(6*Volume/pi)^(1/3) . | Yes |
"Extent" | Ratio of voxels in the region to voxels in the total
bounding box, returned as a scalar. Computed as the value of
Volume divided by the volume of the
bounding box. [Volume/(bounding box width *
bounding box height * bounding box
depth)] | Yes |
"Image" | Bounding box of the region, returned as a volumetric
binary image that is the same size as the bounding box of
the region. The on voxels correspond to
the region, and all other voxels are
off . | Yes |
"Orientation" | Euler angles [2], returned as a 1-by-3 vector. The angles are based on
the right-hand rule. | Yes |
"PrincipalAxisLength" | Length (in voxels) of the major axes of the ellipsoid
that have the same normalized second central moments as the
region, returned as 1-by-3 vector.
regionprops3 sorts the values from
highest to lowest. | Yes |
"Solidity" | Proportion of the voxels in the convex hull that are also
in the region, returned as a scalar. Computed as
Volume/ConvexVolume . | No |
"SubarrayIdx" | Indices used to extract elements inside the object
bounding box, returned as a cell array such that
L(idx{:}) extracts the elements of
L inside the object bounding
box. | Yes |
"SurfaceArea" | Distance around the boundary of the region [1], returned as a scalar. | No |
"Volume" | Count of the actual number of on
voxels in the region, returned as a scalar. Volume
represents the metric or measure of the number of voxels in
the regions within the volumetric binary image,
BW . | Yes |
"VoxelIdxList" | Linear indices of the voxels in the region, returned as a p-element vector. | Yes |
"VoxelList" | Locations of voxels in the region, returned as a
p-by-3 matrix. Each row of the matrix
has the form [x y z] and specifies the
coordinates of one voxel in the region. | Yes |
The voxel value measurement properties in the following table are valid
only when you specify a grayscale volumetric image,
V
.
Voxel Value Measurements
Property Name | Description | Code Generation |
---|---|---|
"MaxIntensity" | Value of the voxel with the greatest intensity in the region, returned as a scalar. | Yes |
"MeanIntensity" | Mean of all the intensity values in the region, returned as a scalar. | Yes |
"MinIntensity" | Value of the voxel with the lowest intensity in the region, returned as a scalar. | Yes |
"VoxelValues" | Value of the voxels in the region, returned as a p-by-1 vector, where p is the number of voxels in the region. Each element in the vector contains the value of a voxel in the region. | Yes |
"WeightedCentroid" | Center of the region based on location and intensity
value, returned as a p -by-3
vector of coordinates. The first element of
WeightedCentroid is the horizontal
coordinate (or x-coordinate) of the
weighted centroid. The second element is the vertical
coordinate (or y-coordinate). The third
element is the planar coordinate (or
z-coordinate). | Yes |
Data Types: char
| string
| cell
V
— Volumetric grayscale image
3-D numeric array
Output Arguments
stats
— Measurement values
table
Measurement values, returned as a table. The number of rows in the table
corresponds to the number of objects in BW
,
, or
CC
.NumObjectsmax(
. The variables
(columns) in each table row denote the properties calculated for each
region, as specified by L
(:))properties
. If the input image
is a categorical label image L
, then
stats
includes an additional variable with the
property "LabelName"
.
The order of the measurement values in stats
is the
same as the sorted objects in binary image BW
, or the
ordered objects specified by CC
or
L
.
References
[1] Lehmann, Gaetan and David Legland. Efficient N-Dimensional surface estimation using Crofton formula and run-length encoding, The Insight Journal, 2012. https://insight-journal.org/browse/publication/852.
[2] Shoemake, Ken, Graphics Gems IV. Edited by Paul S. Heckbert, Morgan Kaufmann, 1994, pp. 222–229.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™. (since R2023a)
Usage notes and limitations:
regionprops3
supports the generation of C code (requires MATLAB® Coder™). Note that if you choose the genericMATLAB Host Computer
target platform,regionprops3
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.Supports only binary images or numeric label images. Input label images of data type categorical are not supported.
Passing a cell array of properties is not supported. Use a comma-separated list instead.
All properties are supported except
"ConvexVolume"
,"ConvexHull"
,"ConvexImage"
,"Solidity"
, and"SurfaceArea"
.
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 R2017bR2023a: Support for C code generation
regionprops3
now supports the generation of
C code (requires MATLAB
Coder).
R2022b: Support for thread-based environments
regionprops3
now supports thread-based
environments.
See Also
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