Image Processing Toolbox

makelut

Construct a lookup table for use with applylut

Syntax

• lut = makelut(fun,n)
  lut = makelut(fun,n,P1,P2,...)
  

Description

lut = makelut(fun,n) returns a lookup table for use with applylut. fun is either a string containing the name of a function or an inline function object. The function should take a 2-by-2 or 3-by-3 matrix of 1's and 0's as input and return a scalar. n is either 2 or 3, indicating the size of the input to fun. 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.

lut = makelut(fun,n,P1,P2,...) passes the additional parameters P1,P2,..., to fun.

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 = inline('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

label2rgb

makeresampler