LookupFile

Function

This allows you to apply a lookup table to any image by reading a text file. The file should consist of an arbitrary number of rows, and each row can have 3 or 4 entries, corresponding to red, green, blue and possibly alpha. Shake will determine the range of the lookup to be applied based on the number of rows in the file - with 'black' always mapping to 0 and 'white' mapping to (n-1), where n is the number of lines in the file. Therefore, if your file contains 256 rows, Shake will assume that your entries are all normalized to be in the range of 0 (black) to 255 (white). If you have 1024 lines in your file, then 'white' will be considered to be a value of 1023. Interpolation between entries is linear, so lookups with only a few entries may show undesirable artifacts. For example, the simple 5-line lookup file shown below...

0   0   0   0
.3  .3  .3  .3
 1   1   1   1
 2   2   2   2
 4   4   4   4

...will produce a lookup that looks like this:

Because of this linear interpolation, you may want to use the standard Lookup node instead for lookups that do not have a large number of points.

Parameters
Type
Defaults
Function
lookupFile
string
  This is the path to the lookup file
channels
string
"rgba" These are the channels the lookup is applied to.


Synopsis

image LookupFile( image, 
  float expression lookupFile,
  float expression channels
);


Script

image = LookupFile( 
  image, 
  "lookupFile", 
  "channels"
);


Command Line

shake -lookupfile lookupfile channels


See Also
Lookup, LookupHSV, LookupHLS, ColorX