Converting Images to ASCII art using Python & Python Imaging Library

Question

I'm currently trying to write a program that converts images into ASCII art in Python using Python Image Library

Here's what I got so far:

import PIL.Image

# ascii characters used to build the output text
ASCII_CHARS = ["@", "#", "S", "%", "?", "*", "+", ";", ":", ",", ".",]

# resize image according to a new width
def resize_image(image, new_width=100):
    width, height = image.size
    ratio = height / width / 1.65
    new_height = int(new_width * ratio)
    resized_image = image.resize((new_width, new_height))
    return(resized_image)

# convert each pixel to grayscale
def grayify(image):
    grayscale_image = image.convert("L")
    return(grayscale_image)

# convert pixels to a string of ASCII characters
def pixels_to_ascii(image):
    pixels = image.getdate()
    characters = "".join([ASCII_CHARS[pixel//25] for pixel in pixels])
    return(characters)

def main(new_width=100):
    # attempt to open image from user-input
    path = input("Enter a valid pathname to an image:\n")
    try:
        image = PIL.Image.open(path)
    except:
        print(path, "is not a valid pathname to an image.")

    # convert image to ASCII
    new_image_data = pixels_to_ascii(grayify(resize_image(image)))

    # format
    pixel_count = len(new_image_data)
    ascii_image = "\n".join(new_image_data[i:(i+new_width)] for i in range(0, pixel_count, new_width))

    # print result
    print(ascii_image)

    # save result to "ascii_image.txt"
    with open("ascii_image.txt", "w") as f:
        f.write(ascii_image)



main()

When I attempt to run my program in command prompt, I get the errors:

"not a valid pathname to an image"

as well as

"UnboundLocalError: local variable 'image' referenced before assignment

I don't understand why I get those errors. Can anyone point me in the right direction?