imgradientxyz
Find directional gradients of 3-D image
Description
Examples
Compute 3-D Directional Image Gradients Using Sobel Method
Read 3-D data and prepare it for processing.
volData = load('mri');
sz = volData.siz;
vol = squeeze(volData.D);
Calculate the directional gradients.
[Gx, Gy, Gz] = imgradientxyz(vol);
Visualize the directional gradients as a montage.
figure, montage(reshape(Gx,sz(1),sz(2),1,sz(3)),'DisplayRange',[]) title('Gradient magnitude along X')
figure, montage(reshape(Gy,sz(1),sz(2),1,sz(3)),'DisplayRange',[]) title('Gradient magnitude along Y')
figure, montage(reshape(Gz,sz(1),sz(2),1,sz(3)),'DisplayRange',[]) title('Gradient magnitude along Z')
Input Arguments
I
— Input image
3-D grayscale image | 3-D binary image
Input image, specified as a 3-D grayscale image or 3-D binary image.
Data Types: single
| double
| int8
| int16
| int32
| int64
| uint8
| uint16
| uint32
| uint64
| logical
method
— Gradient operator
'sobel'
(default) | 'prewitt'
| 'central'
| 'intermediate'
Gradient operator, specified as one of the following values.
Value | Meaning | ||||||
---|---|---|---|---|---|---|---|
| Sobel gradient operator. The gradient of a pixel is a weighted sum of pixels in the 3-by-3-by-3 neighborhood. For example, in the depth (z) direction, the weights in the three planes are:
| ||||||
| Prewitt gradient operator. The gradient of a pixel is a weighted sum of pixels in the 3-by-3-by-3 neighborhood. For example, in the depth (z) direction, the weights in the three planes are:
| ||||||
'central' | Central difference gradient. The
gradient of a pixel is a weighted difference of
neighboring pixels. For example, in the depth
(z) direction, | ||||||
'intermediate' | Intermediate difference gradient. The
gradient of a pixel is the difference between an
adjacent pixel and the current pixel. For example,
in the depth (z) direction,
|
When applying the gradient operator at the boundaries of the
image, imgradientxyz
assumes values outside the
bounds of the image are equal to the nearest image border value. This
behavior is similar to the 'replicate'
boundary
option in imfilter
.
Data Types: char
| string
Output Arguments
Gx
— Horizontal gradient
3-D numeric array
Horizontal gradient, returned as a numeric matrix of
the same size as image I
. The
horizontal (x) axis points in the
direction of increasing column subscripts.
Gx
is of class
double
, unless the input image
I
is of class
single
, in which case
Gx
is of class
single
.
Data Types: single
| double
Gy
— Vertical gradient
3-D numeric array
Vertical gradient, returned as a numeric matrix of the
same size as image I
. The
vertical (y) axis points in the
direction of increasing row subscripts.
Gy
is of class
double
, unless the input image
I
is of class
single
, in which case
Gy
is of class
single
.
Data Types: single
| double
Gz
— Depth gradient
3-D numeric array
Depth gradient, returned as a 3-D numeric array of the
same size as image I
. The depth
(z) axis points in the
direction of increasing plane subscripts.
Gz
is of class
double
, unless the input image
I
is of class
single
, in which case
Gz
is of class
single
.
Algorithms
imgradientxyz
does not normalize the gradient
output. If the range of the gradient output image has to match the
range of the input image, consider normalizing the gradient image,
depending on the method
argument used. For example,
with a Sobel kernel, the normalization factor is 1/44, for Prewitt,
the normalization factor is 1/18.
Extended Capabilities
C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.
Usage notes and limitations:
imgradientxyz
supports the generation of C code (requires MATLAB® Coder™). For more information, see Code Generation for Image Processing.When generating code, the input argument
method
must be a compile-time constant.
GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.
Usage notes and limitations:
When generating code, the input argument
method
must be a compile-time constant.
Version History
Introduced in R2016a
See Also
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