Simple way to get dominant colors from an image in Python

getcolor.py

from PIL import Image, ImageDraw
import argparse
import sys

def get_colors(image_file, numcolors=10, resize=150):
    # Resize image to speed up processing
    img = Image.open(image_file)
    img = img.copy()
    img.thumbnail((resize, resize))

    # Reduce to palette
    paletted = img.convert('P', palette=Image.ADAPTIVE, colors=numcolors)

    # Find dominant colors
    palette = paletted.getpalette()
    color_counts = sorted(paletted.getcolors(), reverse=True)
    colors = list()
    for i in range(numcolors):
        palette_index = color_counts[i][1]
        dominant_color = palette[palette_index*3:palette_index*3+3]
        colors.append(tuple(dominant_color))

    return colors

def save_palette(colors, swatchsize=20, outfile="palette.png" ):
    num_colors = len(colors)
    palette = Image.new('RGB', (swatchsize*num_colors, swatchsize))
    draw = ImageDraw.Draw(palette)

    posx = 0
    for color in colors:
        draw.rectangle([posx, 0, posx+swatchsize, swatchsize], fill=color) 
        posx = posx + swatchsize

    del draw
    palette.save(outfile, "PNG")

if __name__ == '__main__':
    input_file = sys.argv[1]
    output_file = sys.argv[2]
    colors = get_colors(input_file)
    save_palette(colors, outfile = output_file)

A bug at line 19, it should be

for i in range(len(color_counts)):

@lizhiyong2000

A bug at line 19, it should be

for i in range(len(color_counts)):

No bug. numcolors is an integer. You can use it as an index with range(..) from 0 to numcolors-1.