为2020年的第一场雪锦上添花：用 matplotlib 绘制雪花和雪景（转)

来自：https://blog.csdn.net/xufive/article/details/103888070
import numpy as np
import matplotlib.pyplot as plt
from PIL import Image

plt.rcParams['font.sans-serif'] = ['FangSong']  # 指定默认字体
plt.rcParams['axes.unicode_minus'] = False  # 解决中文显示为方块的问题


def rotate(p, d):
    """返回点p绕原点逆时针旋转d度的坐标"""

    a = np.radians(d)
    m = np.array([[np.cos(a), np.sin(a)], [-np.sin(a), np.cos(a)]])
    return np.dot(p, m)


def koch_curve(p, q):
    """将线段pq生成科赫曲线，返回uvw三个点"""

    p, q = np.array(p), np.array(q)
    u = p + (q - p) / 3  # 三等分点u的坐标
    v = q - (q - p) / 3  # 三等分点V的坐标
    w = rotate(v - u, 60) + u  # 线段uv绕u点逆时针旋转60°得到点w的坐标

    return u.tolist(), v.tolist(), w.tolist()


def snow(triangle, k):
    """给定三角形，生成封闭的科赫雪花"""

    for i in range(k):
        result = list()
        t_len = len(triangle)
        for j in range(t_len):
            p = triangle[j]
            q = triangle[(j + 1) % t_len]
            u, v, w = koch_curve(p, q)
            result.extend([p, u, w, v])
        triangle = result.copy()

    triangle.append(triangle[0])
    return triangle


def draw_scenery():
    """绘制雪景图"""

    im = Image.open('普天同庆.jpg')
    bg = np.array(im)
    plt.imshow(bg)  # 绘制背景图

    for i in range(2000):
        x = np.random.randint(80, im.size[0] - 80)
        y = np.random.randint(30, im.size[1] - 30)
        r = np.random.randint(5, 20)
        a = np.random.random() * 0.6 + 0.2
        v = np.array((x - r / 2, y))
        u = np.array((x + r / 2, y))
        w = rotate(v - u, 60) + u

        data = np.array(snow([(u[0], u[1]), (w[0], w[1]), (v[0], v[1])], 5))
        x, y = np.split(data, 2, axis=1)
        plt.plot(x, y, c='#AABBCC', lw=1, ls='-', alpha=a)

    plt.axis('equal')
    plt.show()
    plt.savefig("ss.jpg")


draw_scenery()