Apply geometric transformation to image
[B,RB] = imwarp(A,RA,tform) transforms the spatially referenced image, specified by the image data A and the associated spatial referencing object RA. The output is a spatially referenced image specified by the image data B and the associated spatial referencing object RB.
Code Generation: imwarp supports the generation of efficient, production-quality C/C++ code from MATLAB. When generating code, the geometric transformation object input, tform, must be either affine2d or projective2d. Additionally, the interpolation method and optional parameter names must be string constants. To see a complete list of all the list of toolbox functions that support code generation, see List of Supported Functions with Usage Notes.
I = imread('cameraman.tif');
Create 2-D geometric transformation object.
tform = affine2d([1 0 0; .5 1 0; 0 0 1])
tform = affine2d with properties: T: [3x3 double] Dimensionality: 2
Apply the transformation to the image.
J = imwarp(I,tform); figure, imshow(I), figure, imshow(J)
Visualize 3 slice planes through center of transformed volume.
Read the MRI data into the workspace and visualize it.
s = load('mri'); mriVolume = squeeze(s.D); sizeIn = size(mriVolume); hFigOriginal = figure; hAxOriginal = axes; slice(double(mriVolume),sizeIn(2)/2,sizeIn(1)/2,sizeIn(3)/2); grid on, shading interp, colormap gray
Create a rotation transformation about the Y axis
theta = pi/8; t = [cos(theta) 0 -sin(theta) 0 0 1 0 0 sin(theta) 0 cos(theta) 0 0 0 0 1] tform = affine3d(t);
Apply the transformation.
mriVolumeRotated = imwarp(mriVolume,tform);
Visualize 3 slice planes through center of transformed volume
sizeOut = size(mriVolumeRotated); hFigRotated = figure; hAxRotated = axes; slice(double(mriVolumeRotated),sizeOut(2)/2,sizeOut(1)/2,sizeOut(3)/2); grid on, shading interp, colormap gray
Link views of both axes together
Set view to see affect of rotation
Image to be transformed, specified as a nonsparse, real-valued array of any numeric class or logical.
2-D or 3-D geometric transformation to perform, specified as a geometric transformation object.
If tform is 2-D and ndims(A) > 2, such as for an RGB image, imwarp applies the same 2-D transformation to all 2-D planes along the higher dimensions.
If tform is 3-D, A must be a 3-D image volume.
Displacement field, specified as nonsparse numeric matrix. When A is 2-D, D is an m-by-n-by-2 numeric array. When A is 3-D, D is an m-by-n-by-3 numeric array. The first plane of the displacement field, D(:,:,1) describes the X component of additive displacement that is added to column and row locations in D to produce remapped locations in A. Similarly, D(:,:,2) describes the Y component of additive displacement values. In the 3-D case, D(:,:,3) describes the Z component of additive displacement. The unit of displacement values in D is pixels. When A is m-by-n-by-p and D is m-by-n-by-2, imwarp applies the displacement field to one plane at a time. imwarp assumes that D is referenced to the default intrinsic coordinate system.
Spatial referencing information associated with the image to be transformed, specified as a spatial referencing object.
If tform is a 2-D geometric transformation, RA must be a 2-D spatial referencing object (imref2d).
If tform is a 3-D geometric transformation, RA must be a 3-D spatial referencing object (imref3d).
Form of interpolation used, specified as one of the following character strings:
|'nearest'||Nearest-neighbor interpolation—the output pixel is assigned the value of the pixel that the point falls within. No other pixels are considered.|
Data Types: char
Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside single quotes (' '). You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.Example: J = imwarp(I,tform,'FillValues',) uses white pixels as fill values.
Size and location of output image in world coordinate system, specified as an imref2d or imref3d spatial referencing object. The ImageSize, XWorldLimits, and YWorldLimits properties of the specified spatial referencing object define the size of the output image and the location of the output image in the world coordinate system.
Value used for output pixels outside the input image boundaries, specified as a numeric array. Fill values are used for output pixels when the corresponding inverse transformed location in the input image is completely outside the input image boundaries.
If the input image is 2-D, FillValues must be a scalar.
If the input image is 3-D and the geometric transformation is 3-D, FillValues must be a scalar.
If the input image is N-D and the geometric transformation is 2-D, FillValues may be either scalar or an array whose size matches dimensions 3 to N of the input image.
For example, if the input image is a uint8 RGB image that is 200-by-200-by-3, FillValues can be a scalar or a 3-by-1 array. In this RGB image example, possibilities for FillValues include:
|0||Fill with black|
|[0;0;0]||Fill with black|
|255||Fill with white|
|[255;255;255]||Fill with white|
|[0;0;255]||Fill with blue|
|[255;255;0]||Fill with yellow|
If the input image is 4-D with size 200-by-200-by-3-by-10, FillValues can be a scalar or a 3-by-10 array.
Transformed image, returned as a nonsparse, real-valued array of any numeric class or logical.
Spatial referencing information associated with the transformed image, returned as a spatial referencing object.