Image Processing Toolbox User's Guide |

**Creating TFORM Structures**

After defining the transformation data (Defining the Transformation Data), you must create a `TFORM`

structure to specify the spatial transformation. You use the `maketform`

function to create a `TFORM`

structure. You pass the `TFORM`

structure to the `imtransform`

to perform the transformation. (You can also create a `TFORM`

using the `cp2tform`

function. For more information, see Image Registration.)

The example creates a `TFORM`

structure that specifies the parameters necessary for the translation operation.

To create a `TFORM`

you must specify the type of transformation you want to perform and pass in the transformation data. The example specifies `'affine'`

as the transformation type because translation is an affine transformation but `maketform`

also supports projective transformations. In addition, by using the `custom`

and `composite`

options you can specify a virtually limitless variety of spatial transformations to be used with `imtransform`

. The following table lists the transformation types supported by `maketform`

.

**Contents of a TFORM Structure**

The `TFORM`

structure created by the `maketform`

function is a MATLAB data structure that contains the parameters needed to perform the requested transformation. (These are actually the parameters required by the low-level transformation function `tformarray`

, which `imtransform`

calls to perform the transformation -- see Performing N-Dimensional Spatial Transformations.)

tform_translate = ndims_in: 2 ndims_out: 2 forward_fcn: @fwd_affine inverse_fcn: @inv_affine tdata: [1x1 struct]

The following table describes each of these fields. Note that you do not have to specify the value of these fields; `maketform`

creates this structure.

The `tdata`

field contains the actual transformation matrix that you passed in as an argument or that `maketform`

inferred from the sets of points you specified. For example, the following is the transformation matrix for the forward transformation for the translation in Example: Performing a Translation.

Defining the Transformation Data | Performing the Spatial Transformation |

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