main.py

import os
import sys

from math import ceil, floor

from PIL import Image

RATIO = (1/2.35)
SYMBOL_STRING = '&#.:*"..'
EIGHT_COLOR = [(0, 0, 0),           # 0
               (0, 0, 255),         # 1
               (0, 255, 0),         # 2
               (0, 255, 255),       # 3
               (255, 0, 0),         # 4
               (255, 0, 255),       # 5
               (255, 255, 0),       # 6
               (255, 255, 255)]     # 7

lookup_table = {k: v for k, v in zip(EIGHT_COLOR, SYMBOL_STRING)}

def three_bit(n):
    ''' Convert an image to 3 bit color '''
    return 0 if n <= 128 else 255

def pixel_data(image_path, converter=three_bit, shrink=3.5):
    ''' Returns a list containing rows of pixel data '''
    im = Image.open(image_path)
    height, width = im.size
    # resize
    small = im.resize((int(floor(height/shrink)), int(floor((width/shrink) * RATIO))))
    # convert to n bit color
    small = small.point(converter)
    # load the pixel table for the small n bit image
    pixels = small.load()
    s_height, s_width = small.size
    return [[lookup_table[pixels[x, y]] for x in xrange(s_height)] for y in xrange(s_width)]

if __name__ == '__main__':
    image_path = sys.argv[1]
    data = pixel_data(image_path)
    for row in data:
        print ''.join(row)