TVZAP works on the image that is loaded into the television. It performs the ZAP operation (see HELP ZAP) on those pixels selected by the TV cursor.
SIG=f and TTY have the same meaning as in ZAP. SEARCH is used to select the size of the region which is median filtered. The region is a square box of size 's', where 's' is the argument to the SEARCH word. 's' has a maximum size of 50. If the word SEARCH is not given, the default is a 5 by 5 box. The MASK keyword is the same as for the ZAP command.
The SURGICAL keyword means to test only the pixel directly beneath the cursor for zapping. By default TVZAP (like ZAP or LZAP) will test all pixels within the current median window, and replace them with the median if they exceed the rejection threshold.
After you type TVZAP, the cursor will appear on the screen. The usual cursor keys (see ITV) will then be defined. Other defined keys are:
| Z | perform ZAP operation at position of cursor |
| E | exit from TVZAP |
| S | change size of box used in median filtering |
| T | change rejection threshold |
Move the cursor, in turn, to the regions on the image you want zapped. Hit the Z key each time. The median filtering process will take place, and the program will tell you how many pixels have been zapped.