Create ASCII art from an image

asciiart.py

from PIL import Image, ImageDraw, ImageFont
from colour import Color
import numpy as np

# The function convert an image to ascii art
# f: Input filename
# SC: the horizontal pixel sampling rate. It should be between 0(exclusive) and 1(inclusive). The larger the number, the more details in the output. 
#   If you want the ascii art output be the same size as input, use ~ 1/ font size width. 
# GCF: >0. It's an image tuning factor. If GCF>1, the image will look brighter; if 0<GCF<1, the image will look darker.
# out_f: output filename
# color1, color2, bgcolor: follow W3C color naming https://www.w3.org/TR/css3-color/#svg-color
#
# Copyright 2017, Shanshan Wang, MIT license


def asciiart(in_f, SC, GCF,  out_f, color1='black', color2='blue', bgcolor='white'):

    # The array of ascii symbols from white to black
    chars = np.asarray(list(' .,:irs?@9B&#'))

    # Load the fonts and then get the the height and width of a typical symbol 
    # You can use different fonts here
    font = ImageFont.load_default()
    letter_width = font.getsize("x")[0]
    letter_height = font.getsize("x")[1]

    WCF = letter_height/letter_width

    #open the input file
    img = Image.open(in_f)

    #Based on the desired output image size, calculate how many ascii letters are needed on the width and height
    widthByLetter=round(img.size[0]*SC*WCF)
    heightByLetter = round(img.size[1]*SC)
    S = (widthByLetter, heightByLetter)

    #Resize the image based on the symbol width and height
    img = img.resize(S)
    
    #Get the RGB color values of each sampled pixel point and convert them to graycolor using the average method.
    # Refer to https://www.johndcook.com/blog/2009/08/24/algorithms-convert-color-grayscale/ to know about the algorithm
    img = np.sum(np.asarray(img), axis=2)
    
    # Normalize the results, enhance and reduce the brightness contrast. 
    # Map grayscale values to bins of symbols
    img -= img.min()
    img = (1.0 - img/img.max())**GCF*(chars.size-1)
    
    # Generate the ascii art symbols 
    lines = ("\n".join( ("".join(r) for r in chars[img.astype(int)]) )).split("\n")

    # Create gradient color bins
    nbins = len(lines)
    colorRange =list(Color(color1).range_to(Color(color2), nbins))

    #Create an image object, set its width and height
    newImg_width= letter_width *widthByLetter
    newImg_height = letter_height * heightByLetter
    newImg = Image.new("RGBA", (newImg_width, newImg_height), bgcolor)
    draw = ImageDraw.Draw(newImg)

    # Print symbols to image
    leftpadding=0
    y = 0
    lineIdx=0
    for line in lines:
        color = colorRange[lineIdx]
        lineIdx +=1

        draw.text((leftpadding, y), line, color.hex, font=font)
        y += letter_height

    # Save the image file
    newImg.save(out_f)

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

    inputf = "IQaH96.jpeg"  # Input image file name

    SC = 0.1    # pixel sampling rate in width
    GCF= 2      # contrast adjustment

    asciiart(inputf, SC, GCF, "results.png")   #default color, black to blue
    asciiart(inputf, SC, GCF, "results_pink.png","blue","pink")