tforminv (Image Processing Toolbox)

Apply inverse spatial transformation

Syntax

```
U = tforminv(X,T)
```

Description

U = tforminv(X,T) applies the inverse transformation defined in T to each row of X, if X is a matrix. T is a TFORM struct created with maketform, fliptform, or cp2tform. The argument X is an M-by-T.ndims_out matrix. Each row of X represents a point in T's output space. U is an M-by-T.ndims_out matrix. Each row of U represents a point in T's input space, and is the inverse transformation of the corresponding row of X.

If X is an (N+1)-dimensional array (including an implicit trailing singleton dimension if T.ndims_out is 1), then tforminv applies the transformation to each point X(P1,P2,...,PN,:). size(X,N+1) must equal T.ndims_in. U is an (N+1)-dimensional array containing the results of each transformation in U(P1,P2,...PN,:). size(U,I) equals size(X,I) for I = 1,...,N and size(U,N+1) equals T.ndims_in.

Example

Create an affine transformation that maps the triangle with vertices (0,0), (6,3), (-2,5) to the triangle with vertices (-1,-1), (0,-10), (-2,5).

u = [0 0; 6 3; -2 5];
x = [-1 -1; 0 -10; 4 4];
tform = maketform('affine',u,x);

Validate the mapping by applying tforminv to x.

tforminv(x,tform)  % Result should equal u

tformfwd translate