Function

Use the LookupFile function 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 three or four entries, corresponding to red, green, blue, and possibly alpha. Shake determines the range of the lookup to apply 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 assumes 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” is 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 following simple five-line lookup file produces the following lookup curve:

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

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