pnmcolormap

Create quantization color map for a PNM image. More information: https://netpbm.sourceforge.net/doc/pnmcolormap.html.

• Generate an image using only n_colors or less colors as close as possible to the input image:

pnmcolormap n_colors path/to/input.pnm > path/to/output.ppm

• Use the splitspread strategy for determining the output colors, possibly producing a better result for images with small details:

pnmcolormap -splitspread n_colors path/to/input.pnm > path/to/output.ppm

• Sort the resulting colormap, which is useful for comparing colormaps:

pnmcolormap -sort path/to/input.pnm > path/to/output.ppm