Image to ASCII Art Converter (Python recipe) by FB36

ActiveState Code (http://code.activestate.com/recipes/580702/)

# ASCII Art Generator (Image to ASCII Art Converter)
# FB - 20160925
import sys
if len(sys.argv) != 3:
    print "USAGE:"
    print "[python] img2asciiart.py InputImageFileName OutputTextFileName"
    print "Use quotes if file paths/names contain spaces!"
    sys.exit()
inputImageFileName = sys.argv[1]
OutputTextFileName = sys.argv[2]

from PIL import Image, ImageDraw, ImageFont
font = ImageFont.load_default() # load default bitmap monospaced font
(chrx, chry) = font.getsize(chr(32))
# calculate weights of ASCII chars
weights = []
for i in range(32, 127):
    chrImage = font.getmask(chr(i))
    ctr = 0
    for y in range(chry):
        for x in range(chrx):
            if chrImage.getpixel((x, y)) > 0:
                ctr += 1
    weights.append(float(ctr) / (chrx * chry))

image = Image.open(inputImageFileName)
(imgx, imgy) = image.size
imgx = int(imgx / chrx)
imgy = int(imgy / chry)
# NEAREST/BILINEAR/BICUBIC/ANTIALIAS
image = image.resize((imgx, imgy), Image.BICUBIC)
image = image.convert("L") # convert to grayscale
pixels = image.load()
output = open(OutputTextFileName, "w")
for y in range(imgy):
    for x in range(imgx):
        w = float(pixels[x, y]) / 255
        # find closest weight match
        wf = -1.0; k = -1
        for i in range(len(weights)):
            if abs(weights[i] - w) <= abs(wf - w):
                wf = weights[i]; k = i
        output.write(chr(k + 32))
    output.write("\n")
output.close()