ppmntsc

Adjust colors to NTSC broadcast safe range

TLDR

Convert to NTSC-safe colors

$ ppmntsc [input.ppm] > [output.ppm]

Use PAL limits instead of NTSC

$ ppmntsc --pal [input.ppm] > [output.ppm]

Show count of illegal pixels

$ ppmntsc --verbose [input.ppm] > [output.ppm]

Output only corrected pixels (compliant pixels become black)

$ ppmntsc --correctedonly [input.ppm] > [output.ppm]

SYNOPSIS

ppmntsc [--pal] [--legalonly] [--illegalonly] [--correctedonly] [--verbose] [--debug] [infile]

ppmntsc adjusts the colors in a PPM image to fall within the legal range for NTSC television broadcast. It tests each pixel and reduces saturation for those outside the legal range, while leaving compliant pixels unchanged. Colors that exceed the NTSC signal limits are clipped to the nearest legal value, preventing artifacts like blooming and color bleeding on broadcast displays.The --pal option switches to PAL broadcast limits instead. The --verbose mode reports how many pixels were illegal, helping assess whether the source image is significantly out of gamut. The filtering options (--legalonly, --illegalonly, --correctedonly) allow isolating specific pixels for analysis. Part of the Netpbm toolkit.

PARAMETERS

infile

Input PPM file. Reads from standard input if omitted.

--pal

Use PAL broadcast color limits instead of the default NTSC.

--verbose

Display a count of illegal pixels found.

--debug

Display detailed output listing each illegal color and its corrected version.

--legalonly

Output only compliant pixels; replace non-compliant ones with black.

--illegalonly

Output only non-compliant pixels uncorrected; replace compliant ones with black.

--correctedonly

Output only corrected versions of non-compliant pixels; replace compliant ones with black.

INSTALL

sudo apt install netpbm

sudo dnf install netpbm

sudo pacman -S netpbm

sudo apk add netpbm

sudo zypper install netpbm

brew install netpbm

nix profile install nixpkgs#netpbm

CAVEATS

For video production. Part of the Netpbm suite. The program processes multi-image PPM streams.

HISTORY

ppmntsc was created by Wes Barris at the Minnesota Supercomputer Center as part of the Netpbm toolkit for NTSC color compliance.