SAOtng supports the following scale algorithms internally: . ... Support for other scaling algorithms can be added to SAOtng by writing a program that takes a FITS image as input and generates a scaled (8-bit) FIT image as output. ... Each scale program command line takes $data as stdin and writes the scaled FITS image to stdout. When the scale algorithm is executed, $data will be replaced by a command to retrieve the unscaled data, which then is passed to the scale program. ...