randomAffine2d
Create randomized 2-D affine transformation
Description
creates an tform
= randomAffine2daffinetform2d
object that performs an identity transformation.
specifies the type of affine transformation using name-value arguments.tform
= randomAffine2d(Name,Value
)
Examples
Rotate Image By Random Angle
Read and display an image.
I = imread("kobi.png");
imshow(I)
Create a 2-D affine transformation object that rotates images. The randomAffine2d
function picks the rotation angle randomly from a continuous uniform distribution within the interval [35, 55] degrees.
tform1 = randomAffine2d(Rotation=[35 55]);
Rotate the image and display the result.
J = imwarp(I,tform1); imshow(J)
The transformation object, tform1
, rotates all images by the same amount. To rotate an image by a different randomly selected amount, create a new geometric transformation.
tform2 = randomAffine2d(Rotation=[-10 10]); J2 = imwarp(I,tform2); imshow(J2)
Randomly Rotate Image with Custom Rotation Range
Read and display an image.
I = imread("sherlock.jpg");
imshow(I)
Create a 2-D affine transformation object that rotates images. To select a rotation angle from a custom range, specify the Rotation
name-value argument as a function handle. This example specifies a function called myrange
(defined at the end of the example) that selects an angle from within two disjoint intervals.
tform = randomAffine2d(Rotation=@myrange);
Rotate the image and display the result.
J = imwarp(I,tform); imshow(J)
Supporting Function
This example defines the myrange
function that first randomly selects one of two intervals (-10, 10) and (170, 190) with equal probability. Within the selected interval, the function returns a single random number from a uniform distribution.
function angle = myrange() if randi([0 1],1) a = -10; b = 10; else a = 170; b = 190; end angle = a + (b-a).*rand(1); end
Input Arguments
Name-Value Arguments
Specify optional pairs of arguments as
Name1=Value1,...,NameN=ValueN
, where Name
is
the argument name and Value
is the corresponding value.
Name-value arguments must appear after other arguments, but the order of the
pairs does not matter.
Example: tform = randomAffine2d(XReflection=true)
Before R2021a, use commas to separate each name and value, and enclose
Name
in quotes.
Example: tform = randomAffine2d("XReflection",true)
XReflection
— Random horizontal reflection
false
(default) | true
Random horizontal reflection, specified as 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 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.
Rotation
— Range of rotation
[0 0]
(default) | 2-element numeric vector | function handle
Range of rotation, in degrees, applied to the input image, specified as one of the following.
A 2-element numeric vector. The second element must be larger than or equal to the first element. The rotation angle is picked randomly from a continuous uniform distribution within the specified interval.
A function handle. The function must accept no input arguments and return the rotation angle as a numeric scalar. Use a function handle to pick rotation angles 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 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 one of the following.
A 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.
A 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]
XShear
— Range of horizontal shear
[0 0]
(default) | 2-element numeric vector | function handle
Range of horizontal shear applied to the input image, specified as one of the following. Shear is measured as an angle in degrees, and is in the range (–90, 90).
A 2-element numeric vector. The second element must be larger than or equal to the first element. The horizontal shear angle is picked randomly from a continuous uniform distribution within the specified interval.
A function handle. The function must accept no input arguments and return the horizontal shear angle as a numeric scalar. Use a function handle to pick horizontal shear angles 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]
YShear
— Range of vertical shear
[0 0]
(default) | 2-element numeric vector | function handle
Range of vertical shear applied to the input image, specified as one of the following. Shear is measured as an angle in degrees, and is in the range (–90, 90).
A 2-element numeric vector. The second element must be larger than or equal to the first element. The vertical shear angle is picked randomly from a continuous uniform distribution within the specified interval.
A function handle. The function must accept no input arguments and return the vertical shear angle as a numeric scalar. Use a function handle to pick vertical shear angles 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 vertical 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 one of the following. Translation distance is measured in pixels.
A 2-element numeric vector. The second element must be larger than or equal to the first element. The horizontal translation distance is picked randomly from a continuous uniform distribution within the specified interval.
A function handle. The function must accept no input arguments and return the horizontal translation distance as a numeric scalar. Use a function handle to pick horizontal translation distances 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 one of the following. Translation distance is measured in pixels.
A 2-element numeric vector. The second element must be larger than or equal to the first element. The vertical translation distance is picked randomly from a continuous uniform distribution within the specified interval.
A function handle. The function must accept no input arguments and return the vertical translation distance as a numeric scalar. Use a function handle to pick vertical translation distances 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]
Output Arguments
tform
— Affine transformation
affinetform2d
object
Affine transformation, returned as an affinetform2d
object.
Version History
Introduced in R2019bR2022b: Returns tform
as affinetform2d
object
Starting in R2022b, most Image Processing Toolbox™ functions create and perform geometric transformations using the premultiply
convention. Accordingly, the randomAffine2d
function now returns the
output argument tform
as an affinetform2d
object, which supports the premultiply convention. Before, the function returned
tform
as an affine2d
object, which supports the
postmultiply convention. For more information, see Migrate Geometric Transformations to Premultiply Convention.
See Also
imwarp
| randomWindow2d
| centerCropWindow2d
Topics
- Augment Images for Deep Learning Workflows (Deep Learning Toolbox)
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