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# fitgeotrans() - Image Processing

### Syntax

### Example

### Output / Return Value

### Limitations

### Alternatives / See Also

### Reference

tform = fitgeotrans(movingPoints,fixedPoints,transformationType) takes the pairs of control points, movingPoints and fixedPoints, and uses them to infer the geometric transformation, specified by transformationType. tform = fitgeotrans(movingPoints,fixedPoints,'polynomial',degree) fits an images.geotrans.PolynomialTransformation2D object to control point pairs movingPoints and fixedPoints. Specify the degree of the polynomial transformation degree, which can be 2, 3, or 4.tform = fitgeotrans(movingPoints,fixedPoints,'pwl') fits an images.geotrans.PiecewiseLinearTransformation2D object to control point pairs movingPoints and fixedPoints. This transformation maps control points by breaking up the plane into local piecewise-linear regions in which a different affine transformation maps control points in each local region.tform = fitgeotrans(movingPoints,fixedPoints,'lwm',n) fits an images.geotrans.LocalWeightedMeanTransformation2D object to control point pairs movingPoints and fixedPoints. The local weighted mean transformation creates a mapping, by inferring a polynomial at each control point using neighboring control points. The mapping at any location depends on a weighted average of these polynomials. The n closest points are used to infer a second degree polynomial transformation for each control point pair.Code Generation support: Yes.MATLAB Function Block support: Yes.

tform = fitgeotrans(movingPoints,fixedPoints,transformationType) exampletform = fitgeotrans(movingPoints,fixedPoints,'polynomial',degree)tform = fitgeotrans(movingPoints,fixedPoints,'pwl')tform = fitgeotrans(movingPoints,fixedPoints,'lwm',n)

Create Geometric Transformation for Image AlignmentOpen This Example This example shows how to create a geometric transformation that can be used to align two images. Create a checkerboard image and rotate it to create a misaligned image.I = checkerboard; J = imrotate(I,30); imshowpair(I,J,'montage') Define some control points on the fixed image (the checkerboard) and moving image (the rotated checkerboard). You can define points interactively using the Control Point Selection tool.fixedPoints = [11 11; 41 71]; movingPoints = [14 44; 70 81]; Create a geometric transformation that can be used to align the two images, returned as an affine2d geometric transformation object.tform = fitgeotrans(movingPoints,fixedPoints,'NonreflectiveSimilarity') tform = affine2d with properties: T: [3x3 double] Dimensionality: 2 Use the tform estimate to resample the rotated image to register it with the fixed image. The regions of color (green and magenta) in the false color overlay image indicate error in the registration due to lack of precise correspondence in the control points.Jregistered = imwarp(J,tform,'OutputView',imref2d(size(I))); falsecolorOverlay = imfuse(I,Jregistered); figure imshow(falsecolorOverlay,'InitialMagnification','fit'); Recover angle and scale of the transformation by checking how a unit vector parallel to the x-axis is rotated and stretched.u = [0 1]; v = [0 0]; [x, y] = transformPointsForward(tform, u, v); dx = x(2) - x(1); dy = y(2) - y(1); angle = (180/pi) * atan2(dy, dx) scale = 1 / sqrt(dx^2 + dy^2) angle = 29.9816 scale = 1.0006