randomAffine3d

Create randomized 3-D affine transformation

Syntax

tform = randomAffine3d

tform = randomAffine3d(Name,Value)

Description

tform = randomAffine3d creates an affine3d object with default property values consistent with the identity transformation.

tform = randomAffine3d(Name,Value) specifies the type of affine transformations using name-value pair arguments.

Examples

Randomly Shear 3-D Volume

Create a sample volume.

volumeCube = ones(100,100,100);
figure
volshow(volumeCube);

Create an affine3d transformation object that shears 3-D volumes. The randomAffine3d function picks a shear amount randomly from a continuous uniform distribution within the interval [40, 60] degrees. randomAffine3d picks a random shear direction aligned with the x-, y-, or z-axis.

tform1 = randomAffine3d('Shear',[40 60]);
J1 = imwarp(volumeCube,tform1);
figure
volshow(J1);

To shear a volume by a different randomly selected amount, create a new affine3d transformation object. Note the difference in the shear direction.

tform2 = randomAffine3d('Shear',[40 60]);
J2 = imwarp(volumeCube,tform2);
figure
volshow(J2);

Input Arguments

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

Example: tform = randomAffine3d('XReflection',true)

'XReflection' — Random horizontal reflection

false (default) | true

Random horizontal reflection, specified as the comma-separated pair consisting of 'XReflection' and false or true. When XReflection is true (1), the transformation tform reflects images horizontally with 50% probability. By default, the transformation does not reflect images in the horizontal direction.

'YReflection' — Random vertical reflection

false (default) | true

Random vertical reflection, specified as the comma-separated pair consisting of 'YReflection' and false or true. When YReflection is true (1), the transformation tform reflects images vertically with 50% probability. By default, the transformation does not reflect images in the vertical direction.

'ZReflection' — Random reflection along depth

false (default) | true

Random reflection along the depth direction, specified as the comma-separated pair consisting of 'ZReflection' and false or true. When ZReflection is true (1), the transformation tform reflects images along the depth direction with 50% probability. By default, the transformation does not reflect images in the depth direction.

'Rotation' — Range of rotation

[0 0] (default) | 2-element numeric vector | function handle

Range of rotation applied to the input image, specified as the comma-separated pair consisting of 'Rotation' and one of the following. Rotation is measured in degrees.

• 2-element numeric vector. The second element must be larger than or equal to the first element. randomAffine3d picks a rotation angle randomly from a continuous uniform distribution within the specified interval. randomAffine3d selects a random axis of rotation from the unit sphere.

• function handle of the form

  [rotationAxis,theta] = selectRotation

  The function selectRotation must accept no input arguments. The function must return two output arguments: rotationAxis, a 3-element vector defining the axis of rotation, and theta, a rotation angle in degrees.

  Use a function handle to pick rotation angles from a disjoint interval or using a nonuniform probability distribution. You can also use a function handle to specify an axis of rotation. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not rotate images.

Example: [-45 45]

'Scale' — Range of uniform scaling

[1 1] (default) | 2-element numeric vector | function handle

Range of uniform (isotropic) scaling applied to the input image, specified as the comma-separated pair consisting of 'Scale' and one of the following.

• 2-element numeric vector. The second element must be larger than or equal to the first element. The scale factor is picked randomly from a continuous uniform distribution within the specified interval.

• function handle. The function must accept no input arguments and return the scale factor as a numeric scalar. Use a function handle to pick scale factors from a disjoint interval or using a nonuniform probability distribution. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not scale images.

Example: [0.5 4]

'Shear' — Range of shear

[0 0] (default) | 2-element numeric vector | function handle

Range of shear applied to the input image, specified as the comma-separated pair consisting of 'Shear' and one of the following. Shear is measured as an angle in degrees, and is in the range (–90, 90).

• 2-element numeric vector. The second element must be larger than or equal to the first element. The shear angle is picked randomly from a continuous uniform distribution within the specified interval. randomAffine3d applies shear with uniform randomness to one of the principle x-, y-, and z-directions with respect to one of the two possible orthogonal directions.

• function handle. The function must accept no input arguments and return the shear angle as a numeric scalar. Use a function handle to pick a shear angle from a disjoint interval or using a nonuniform probability distribution. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not shear images in the horizontal direction.

Example: [0 45]

'XTranslation' — Range of horizontal translation

[0 0] (default) | 2-element numeric vector | function handle

Range of horizontal translation applied to the input image, specified as the comma-separated pair consisting of 'XTranslation' and one of the following. Translation distance is measured in pixels.

• 2-element numeric vector. The second element must be larger than or equal to the first element. The translation distance is picked randomly from a continuous uniform distribution within the specified interval.

• function handle. The function must accept no input arguments and return the translation distance as a numeric scalar. Use a function handle to pick a translation distance from a disjoint interval or using a nonuniform probability distribution. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not translate images in the horizontal direction.

Example: [-5 5]

'YTranslation' — Range of vertical translation

[0 0] (default) | 2-element numeric vector | function handle

Range of vertical translation applied to the input image, specified as the comma-separated pair consisting of 'YTranslation' and one of the following. Translation distance is measured in pixels.

• 2-element numeric vector. The second element must be larger than or equal to the first element. The translation distance is picked randomly from a continuous uniform distribution within the specified interval.

• function handle. The function must accept no input arguments and return the translation distance as a numeric scalar. Use a function handle to pick a translation distance from a disjoint interval or using a nonuniform probability distribution. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not translate images in the vertical direction.

Example: [-5 5]

'ZTranslation' — Range of translation along depth

[0 0] (default) | 2-element numeric vector | function handle

Range of translation along the depth direction applied to the input image, specified as the comma-separated pair consisting of 'ZTranslation' and one of the following. Translation distance is measured in pixels.

• 2-element numeric vector. The second element must be larger than or equal to the first element. The translation distance is picked randomly from a continuous uniform distribution within the specified interval.

• function handle. The function must accept no input arguments and return the translation distance as a numeric scalar. Use a function handle to pick a translation distance from a disjoint interval or using a nonuniform probability distribution. For more information about function handles, see Create Function Handle.

By default, the transformation tform does not translate images in the depth direction.

Example: [-5 5]

Output Arguments

tform — Affine transformation

affine3d object

Affine transformation, specified as an affine3d object.