LumaKey

Function
This creates a key in the alpha channels based on overall luminance. Values below loVal are set to zero, and values above hiVal are set to 1. Values in between are ramped. You also have roll-off control, plus a mMult toggle.

This is a fast way to place the luminance of the image into the alpha layer, but this could also be done with a Reorder - rgbl.

Parameters
Type
Defaults
Function
loVal
float
0 Any pixel below this value (as calculated per its luminance) turns black.
hiVal
float
1 Any pixel above this value (as calculated by its luminanace) turns white.
lo,hiSmooth
float
0,0,

A rolloff factor to provide a smooth dropoff.

mMult
int
0

automatic pre-multiplification of the RGB channels.

0 = no pre-multiply
1 = pre-multiply

Synopsis

image LumaKey( 
  image, 
  float loVal, 
  float hiVal, 
  float loSmooth, 
  float hiSmooth,
  int mMult
);

Script

image = LumaKey( 
  image, 
  loVal, 
  hiVal, 
  loSmooth, 
  hiSmooth, 
  mMult
);

Command Line

shake -lumakey loVal hiVal loSmooth etc...

See Also
ChromaKey, DepthKey, Primatte