You can do it like this with ImageMagick on the command line. This will quantize the image to 8 colors and list them in descending order of occurance: conver

You can do it like this with ImageMagick on the command line. This will quantize the image to 8 colors and list them in descending order of occurance: convert image.jpg -resize 400x400 -format %c -dither None -quantize LAB -colors 8 -depth 8 histogram:info:- | sort -r