图片转字符画脚本。
Picture to character drawing script.
基本逻辑为将原图按照一定比例转为灰度图，根据不同灰度值确定不同的字符以形成字符画形式。
The basic logic is to convert the original image into a grayscale image according to a certain proportion, and determine different characters based on different grayscale values to form a character drawing form.