Prints an ASCII-character version of an image.

img2ascii.py

#! /usr/bin/env python3

# Usage: img2ascii <img_file> <col_width> 

from PIL import Image
import numpy as np

ASCII_CHARS = np.array(list(
    " .:-=+*#%@"
))
# simpler ramp often looks better than huge ones

def rescale(pixels, low=2, high=98):
    # percentile-based contrast stretch (prevents blowout)
    lo = np.percentile(pixels, low)
    hi = np.percentile(pixels, high)
    pixels = np.clip(pixels, lo, hi) 
    return (pixels - lo) / (hi - lo) * 255

def image_to_ascii(path, width=140, gamma=1.2, invert=False):
    img = Image.open(path).convert("L")
    
    aspect_ratio = img.height / img.width
    height = int(aspect_ratio * width * 0.55)
    img = img.resize((width, height))
    
    pixels = np.array(img).astype(float)
    
    # 🔑 key: percentile stretch instead of min/max
    pixels = rescale(pixels, 3, 97)
    
    # gamma correction (controls brightness distribution)
    pixels = 255 * ((pixels / 255) ** gamma)
    
    if invert: 
        pixels = 255 - pixels
    
    indices = (pixels / 255 * (len(ASCII_CHARS) - 1)).astype(int)
    ascii_img = ASCII_CHARS[indices]
    
    return "\n".join("".join(row) for row in ascii_img)


if __name__ == "__main__":
    import sys
    print(image_to_ascii(sys.argv[1], width=int(sys.argv[2]), gamma=1.3))

Totally generated by ChatGPT. Not actually "mine". Though we did iterate over a few versions to get it the way I liked it.