makelut (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Construct a lookup table for use with applylut

Syntax

```
lut = makelut(fun,n)
```

Description

lut = makelut(fun,n) returns a lookup table for use with applylut. fun is a function that accepts an n-by-n matrix of 1's and 0's as input and return a scalar. n can be either 2 or 3. makelut creates lut by passing all possible 2-by-2 or 3-by-3 neighborhoods to fun, one at a time, and constructing either a 16-element vector (for 2-by-2 neighborhoods) or a 512-element vector (for 3-by-3 neighborhoods). The vector consists of the output from fun for each possible neighborhood.

fun must be a function handle.

Class Support

lut is returned as a vector of class double.

Example

In this example, the function returns 1 (true) if the number of 1's in the neighborhood is 2 or greater, and returns 0 (false) otherwise. makelut then uses the function to construct a lookup table for 2-by-2 neighborhoods.

f = @(x) (sum(x(:)) >= 2);
lut = makelut(f,2)

lut =

     0
     0
     0
     1
     0
     1
     1
     1
     0
     1
     1
     1
     1
     1
     1
     1

See Also

applylut

makecform makeresampler