A python script to convert an image to ASCII image, txt file.

img2ascii.py

# Python code to convert an image to ASCII image.
import sys, random, argparse
import numpy as np
import math

from PIL import Image

# gray scale level values from:
# http://paulbourke.net/dataformats/asciiart/

# 70 levels of gray
gscale1 = "$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/\|()1{}[]?-_+~<>i!lI;:,\"^`'. "

# 10 levels of gray
gscale2 = '@%#*+=-:. '

def getAverageL(image):

        """
        Given PIL Image, return average value of grayscale value
        """
        # get image as numpy array
        im = np.array(image)

        # get shape
        w,h = im.shape

        # get average
        return np.average(im.reshape(w*h))

def covertImageToAscii(fileName, cols, scale, moreLevels):
        """
        Given Image and dims (rows, cols) returns an m*n list of Images
        """
        # declare globals
        global gscale1, gscale2

        # open image and convert to grayscale
        image = Image.open(fileName).convert('L')

        # store dimensions
        W, H = image.size[0], image.size[1]
        print("input image dims: %d x %d" % (W, H))

        # compute width of tile
        w = W/cols

        # compute tile height based on aspect ratio and scale
        h = w/scale

        # compute number of rows
        rows = int(H/h)

        print("cols: %d, rows: %d" % (cols, rows))
        print("tile dims: %d x %d" % (w, h))

        # check if image size is too small
        if cols > W or rows > H:
                print("Image too small for specified cols!")
                exit(0)

        # ascii image is a list of character strings
        aimg = []
        # generate list of dimensions
        for j in range(rows):
                y1 = int(j*h)
                y2 = int((j+1)*h)

                # correct last tile
                if j == rows-1:
                        y2 = H

                # append an empty string
                aimg.append("")

                for i in range(cols):

                        # crop image to tile
                        x1 = int(i*w)
                        x2 = int((i+1)*w)

                        # correct last tile
                        if i == cols-1:
                                x2 = W

                        # crop image to extract tile
                        img = image.crop((x1, y1, x2, y2))

                        # get average luminance
                        avg = int(getAverageL(img))

                        # look up ascii char
                        if moreLevels:
                                gsval = gscale1[int((avg*69)/255)]
                        else:
                                gsval = gscale2[int((avg*9)/255)]

                        # append ascii char to string
                        aimg[j] += gsval

        # return txt image
        return aimg

# main() function
def main():
        # create parser
        descStr = "This program converts an image into ASCII art."
        parser = argparse.ArgumentParser(description=descStr)
        # add expected arguments
        parser.add_argument('--file', dest='imgFile', required=True)
        parser.add_argument('--scale', dest='scale', required=False)
        parser.add_argument('--out', dest='outFile', required=False)
        parser.add_argument('--cols', dest='cols', required=False)
        parser.add_argument('--morelevels',dest='moreLevels',action='store_true')

        # parse args
        args = parser.parse_args()

        imgFile = args.imgFile

        # set output file
        outFile = 'out.txt'
        if args.outFile:
                outFile = args.outFile

        # set scale default as 0.43 which suits
        # a Courier font
        scale = 0.43
        if args.scale:
                scale = float(args.scale)

        # set cols
        cols = 80
        if args.cols:
                cols = int(args.cols)

        print('generating ASCII art...')
        # convert image to ascii txt
        aimg = covertImageToAscii(imgFile, cols, scale, args.moreLevels)

        # open file
        f = open(outFile, 'w')

        # write to file
        for row in aimg:
                f.write(row + '\n')

        # cleanup
        f.close()
        print("ASCII art written to %s" % outFile)

# call main
if __name__ == '__main__':
        main()