matplotlib使用

参考
https://blog.youkuaiyun.com/qq_34337272/article/details/79555544

子图设置
https://blog.youkuaiyun.com/wuzlun/article/details/80053277

等高线参考
https://www.jb51.net/article/130617.htm

plt内容转成numpy：

   fig.canvas.draw()

    # Get the RGBA buffer from the figure
    w, h = fig.canvas.get_width_height()
    buf = np.fromstring(fig.canvas.tostring_argb(), dtype=np.uint8)
    buf.shape = (w, h, 4)

    # canvas.tostring_argb give pixmap in ARGB mode. Roll the ALPHA channel to have it in RGBA mode
    buf = np.roll(buf, 3, axis=2)
    return buf