pnmcolormap
Generate color palette from PNM images
TLDR
Generate color map with N colors
$ pnmcolormap [256] [image.ppm] > [colormap.ppm]
Use median cut algorithm$ pnmcolormap -center [16] [image.ppm] > [colormap.ppm]
Spread colors evenly$ pnmcolormap -spreadluminosity [256] [image.ppm] > [colormap.ppm]
From multiple images$ pnmcolormap [256] [image1.ppm] [image2.ppm] > [colormap.ppm]
SYNOPSIS
pnmcolormap [options] ncolors [pnmfile...]
DESCRIPTION
pnmcolormap creates a color map (palette) from an image using median cut quantization. The output is a small image where each pixel is a color from the palette.
Used with pnmremap for color reduction.
PARAMETERS
ncolors
Maximum colors in map.-center
Use center of cluster.-meancolor
Use mean color of cluster.-meanpixel
Use mean weighted by pixel count.-spreadbrightness
Spread by brightness.-spreadluminosity
Spread by luminosity.
EXAMPLES
$ # Create 256-color palette
pnmcolormap 256 photo.ppm > palette.ppm
# Reduce colors using map
pnmcolormap 16 image.ppm > map.ppm
pnmremap -mapfile=map.ppm image.ppm > reduced.ppm
# Combined color reduction
pnmcolormap 256 image.ppm | pnmremap -mapfile=- image.ppm > reduced.ppm
pnmcolormap 256 photo.ppm > palette.ppm
# Reduce colors using map
pnmcolormap 16 image.ppm > map.ppm
pnmremap -mapfile=map.ppm image.ppm > reduced.ppm
# Combined color reduction
pnmcolormap 256 image.ppm | pnmremap -mapfile=- image.ppm > reduced.ppm
CAVEATS
Output is the colormap, not the remapped image. Use pnmremap to apply. Part of Netpbm.
HISTORY
pnmcolormap is part of Netpbm, implementing median-cut color quantization algorithm.
SEE ALSO
pnmremap(1), ppmquant(1), ppmquantall(1), netpbm(1)