问一下阴阳师py脚本的问题

[World'sdream]

最近看了个阴阳师的py脚本
https://blog.csdn.net/zydarChen/article/details/77587967?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522160022988119725264617497%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fall.%2522%257D&request_id=160022988119725264617497&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~all~first_rank_v2~rank_v25-16-77587967.pc_search_result_cache&utm_term=python阴阳师游戏脚本&spm=1018.2118.3001.4187

对于这个相对坐标有些不太明白

def get_posx(x, window_size):  # 返回x相对坐标
    return (window_size[2] - window_size[0]) * x / 870


def get_posy(y, window_size):  # 返回y相对坐标
    return (window_size[3] - window_size[1]) * y / 520

topx, topy = window_size[0], window_size[1]
img_ready = ImageGrab.grab((topx + get_posx(500, window_size), topy + get_posy(480, window_size),
                            topx + get_posx(540, window_size), topy + get_posy(500, window_size)))
# 查看图片
im_ready.show()

这个870和520是指游戏界面的窗口大小吗？
window_size[2] - window_size[0]应该是游戏窗口的宽吧，这和870不是近乎相等的吗？
没太搞懂这个公式
希望能解答一下。