pnmquant
Reduce color count in PNM images
TLDR
Reduce colors
$ pnmquant [256] [input.pnm] > [output.pnm]
Use center-of-box color selection$ pnmquant -center [16] [input.pnm] > [output.pnm]
Apply Floyd-Steinberg dithering$ pnmquant -floyd [256] [input.pnm] > [output.pnm]
Quantize to a predefined colormap$ pnmquant -mapfile [mapfile.pnm] [256] [input.pnm] > [output.pnm]
SYNOPSIS
pnmquant [options] ncolors [file]
DESCRIPTION
pnmquant reduces the number of colors in a PNM image to a specified count using the median-cut color quantization algorithm. This is useful for preparing images for formats with limited color palettes or for reducing file size.The -floyd option enables Floyd-Steinberg dithering to simulate more colors by distributing quantization error to neighboring pixels. The -mapfile option allows quantizing to a pre-defined color palette from another image. Part of the Netpbm toolkit; this is a wrapper script that calls pnmcolormap and pnmremap internally.
PARAMETERS
ncolors
Target number of colors.-floyd, -fs
Enable Floyd-Steinberg dithering to improve visual quality.-nofloyd, -nofs
Disable dithering (default).-center
Choose the center of each color box as the representative color.-meancolor
Choose the mean of all colors in each box (default).-meanpixel
Choose the mean weighted by pixel count in each box.-spreadbrightness
Spread boxes based on brightness range rather than color population.-spreadluminosity
Spread boxes based on luminosity range.-mapfile file
Quantize to a predefined colormap from file.
SEE ALSO
ppmquant(1), pnmcolormap(1), pnmremap(1), pnmdepth(1)
