turtle 实现clip_rule=“evenodd”

以下是使用turtle模块实现clip_rule="evenodd"的示例代码：

import turtle

# 设置画布大小和背景颜色
turtle.setup(800, 600)
turtle.bgcolor("white")

# 设置起始点和裁剪路径
start = (-200, 0)
clip_path = [(0, 200), (200, 0), (0, -200), (-200, 0)]

# 绘制起始点和裁剪路径
turtle.penup()
turtle.goto(start)
turtle.dot(10, "red")
turtle.pendown()
for point in clip_path:
    turtle.goto(point)
turtle.goto(start)

# 设置要裁剪的多边形
poly = [(0, 0), (100, 150), (-50, 200), (-150, 100)]

# 绘制要裁剪的多边形
turtle.penup()
turtle.goto(poly[0])
turtle.pendown()
for point in poly:
    turtle.goto(point)
turtle.goto(poly[0])

# 进行裁剪
new_poly = []
for i in range(len(clip_path)):
    p1, p2 = clip_path[i-1], clip_path[i]
    inside_points = []
    for j in range(len(poly)):
        p3, p4 = poly[j-1], poly[j]
        if (p4[1] > p2[1] and p3[1] <= p2[1]) or (p3[1] > p2[1] and p4[1] <= p2[1]):
            x = (p2[0] - p1[0]) * (p3[1] - p1[1]) / (p2[1] - p1[1]) + p1[0]
            inside_points.append((x, p3[1]))
        elif (p4[1] == p2[1] and p4[0] <= p2[0]) or (p3[1] == p2[1] and p3[0] <= p2[0]):
            inside_points.append(p3)
    if len(inside_points) > 0:
        inside_points.sort()
        if len(new_poly) > 0 and inside_points[0] == new_poly[-1]:
            new_poly.extend(inside_points[1:])
        else:
            new_poly.extend(inside_points)
new_poly.append(new_poly[0])

# 绘制裁剪后的多边形
turtle.penup()
turtle.goto(new_poly[0])
turtle.pendown()
turtle.begin_fill()
for point in new_poly[1:]:
    turtle.goto(point)
turtle.goto(new_poly[0])
turtle.end_fill()

# 隐藏画笔
turtle.hideturtle()

# 显示画布
turtle.done()

该代码使用奇偶规则（evenodd）进行多边形裁剪。首先，绘制了起始点和裁剪路径。然后，定义了要裁剪的多边形，并绘制了它。接下来，使用奇偶规则进行裁剪，并绘制裁剪后的多边形。最后，隐藏画笔并显示画布。