affine3d
3-D affine geometric transformation
Description
An affine3d object stores information about a 3-D affine
geometric transformation and enables forward and inverse transformations.
Creation
You can create an affine3d object using the following
methods:
imregtform— Estimates a geometric transformation that maps a moving image to a fixed image using similarity optimizationrandomAffine3d— Creates a randomized 3-D affine transformationThe
affine3dfunction described here
Description
tform = affine3d creates an affine3d
object with default property settings that correspond to the identity
transformation.
tform = affine3d( sets the
property A)T with a valid affine transformation defined by
nonsingular matrix A.
Properties
Object Functions
invert | Invert geometric transformation |
isRigid | Determine if transformation is rigid transformation |
isSimilarity | Determine if transformation is similarity transformation |
isTranslation | Determine if transformation is pure translation |
outputLimits | Find output spatial limits given input spatial limits |
transformPointsForward | Apply forward geometric transformation |
transformPointsInverse | Apply inverse geometric transformation |
Examples
Define 3-D Affine Transformation Object for Anisotropic Scaling
Create an affine3d object that scales a 3-D image by a different factor in each dimension.
Sx = 1.2; Sy = 1.6; Sz = 2.4; tform = affine3d([Sx 0 0 0; 0 Sy 0 0; 0 0 Sz 0; 0 0 0 1])
tform =
affine3d with properties:
T: [4x4 double]
Dimensionality: 3
Load a 3-D volume into the workspace.
load('mri');
D = squeeze(D);Apply the geometric transformation to the image using imwarp.
B = imwarp(D,tform);
Visualize an axial slice through the center of each volume to see the effect of scale translation. Note that the center slice of the transformed volume has a different index than the center slice of the original volume because of the scaling in the z-dimension.
figure
imshowpair(D(:,:,14),B(:,:,33),'montage');
The original image is on the left, and the transformed image is on the right. The transformed image is scaled more in the vertical direction than in the horizontal direction, as expected since Sy is larger than Sx.