There are applications that mask pixels if their values meet certain criteria.
SETMAGIC flags those pixels with a nominated value. It is most useful during conversion of imported data whose data system uses bad-pixel values different from Starlink's.
FFCLEAN removes defects smaller than a nominated size from an image or vector NDF . It flags those pixels that deviate from a smoothed version of the NDF by more than some number of standard deviations from the local mean.
ERRCLIP flags pixels that have errors larger than some supplied limit or signal-to-noise ratios below a threshold. The errors come from the VARIANCE component of the NDF. Thus you can exclude unreliable data from analysis.
THRESH flags pixels that have data values within or outside some specified range.
KAPPA --- Kernel Application Package