MASK tells VISTA programs to ignore the specified pixels when doing computations.
The command UNMASK is the opposite of MASK; it tells the programs to stop ignoring the specified pixels. UNMASK can be used without options to unmask all pixels.
You can type UNMASK without any options to tell the routines to use all the pixels. Remember that rows and columns are often numbered from ZERO. The row or column numbers specified in MASK are the same as those given by the 'D' option in the ITV command, but remember that if the TV image is compressed, the 'D' option will not give the exact location of certain features in the image. Use the BOX option in the TV command to show smaller sections of an image when finding features you want to mask.
The mask may be saved on the disk with SAVE, and retrieved later with GET.
Not all VISTA commands recognize masked pixels. The ones that do are: ABX, AUTOMARK, MN, CROSS, INTERP, MASH, and SURFACE.