美丽Python：将图片转换成ASCII图案的艺术

很多年前，我还在大学上学，参加了一个由FOSSEE组织的学习小组，在那里，我第一次知道了“Python”，并深深的喜欢上了它。它的简单、对复杂问题的优雅解决方案让我吃惊。下面的这个图片转ASCII码工具就是我在这个学习小组里学到的。

工作原理

我首先将给定的图片缩放到一个适合用ASCII表现的分辨率尺寸。让后再将图片转换成灰度级图片(黑白图片)。在黑白图片模式下，灰度有256个等级，换句话说，每个像素的明暗度是用一个8 bit的值表示。0 表示颜色是黑色，256表示颜色是白色。我们把0-256分成11个小区间，每一个小区间用一个ASCII字符表示。并且字符表现出的颜色深浅要和这个区间的灰度相匹配。我使用PIL库处理图片。下面的代码写的很明白，你一定能看懂。对于不同的图片，输出的效果可能有些不同，效果有好有差，但你可以通过调整这11个ASCII来测试生成的效果。

依赖的库

PIL(Python Imaging Library)

在Ubuntu环境下

$ sudo pip install Pillow

代码:

from PIL import Image

ASCII_CHARS = [ '#', '?', '%', '.', 'S', '+', '.', '*', ':', ',', '@']

def scale_image(image, new_width=100):
    """Resizes an image preserving the aspect ratio.
    """
    (original_width, original_height) = image.size
    aspect_ratio = original_height/float(original_width)
    new_height = int(aspect_ratio * new_width)

    new_image = image.resize((new_width, new_height))
    return new_image

def convert_to_grayscale(image):
    return image.convert('L')

def map_pixels_to_ascii_chars(image, range_width=25):
    """Maps each pixel to an ascii char based on the range
    in which it lies.

    0-255 is divided into 11 ranges of 25 pixels each.
    """

    pixels_in_image = list(image.getdata())
    pixels_to_chars = [ASCII_CHARS[pixel_value/range_width] for pixel_value in
            pixels_in_image]

    return "".join(pixels_to_chars)

def convert_image_to_ascii(image, new_width=100):
    image = scale_image(image)
    image = convert_to_grayscale(image)

    pixels_to_chars = map_pixels_to_ascii_chars(image)
    len_pixels_to_chars = len(pixels_to_chars)

    image_ascii = [pixels_to_chars[index: index + new_width] for index in
            xrange(0, len_pixels_to_chars, new_width)]

    return "\n".join(image_ascii)

def handle_image_conversion(image_filepath):
    image = None
    try:
        image = Image.open(image_filepath)
    except Exception, e:
        print "Unable to open image file {image_filepath}.".format(image_filepath=image_filepath)
        print e
        return

    image_ascii = convert_image_to_ascii(image)
    print image_ascii

if __name__=='__main__':
    import sys

    image_file_path = sys.argv[1]
    handle_image_conversion(image_file_path)

欢迎报告bug和提出改进意见！

(英文，CC Licensed)