findbounds (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Find output bounds for spatial transformation

Syntax

```
outbounds = findbounds(TFORM,inbounds)
```

Description

outbounds = findbounds(TFORM,inbounds) estimates the output bounds corresponding to a given spatial transformation and a set of input bounds. TFORM is a spatial transformation structure as returned by maketform. inbounds is 2-by-NUM_DIMS matrix. The first row of inbounds specifies the lower bounds for each dimension, and the second row specifies the upper bounds. NUM_DIMS has to be consistent with the ndims_in field of TFORM.

outbounds has the same form as inbounds. It is an estimate of the smallest rectangular region completely containing the transformed rectangle represented by the input bounds. Since outbounds is only an estimate, it might not completely contain the transformed input rectangle.

Notes

imtransform uses findbounds to compute the 'OutputBounds' parameter if the user does not provide it.

If TFORM contains a forward transformation (a nonempty forward_fcn field), then findbounds works by transforming the vertices of the input bounds rectangle and then taking minimum and maximum values of the result.

If TFORM does not contain a forward transformation, then findbounds estimates the output bounds using the Nelder-Mead optimization function fminsearch. If the optimization procedure fails, findbounds issues a warning and returns outbounds = inbounds.

Example

inbounds = [0 0; 1 1]
tform = maketform('affine',[2 0 0; .5 3 0; 0 0 1])
outbounds = findbounds(tform, inbounds)

filter2 fliptform