在matplotlib中绘制多边形的联合

Question

我试图绘制几个多边形的联合matplotlib,具有一定的alpha级别.我目前的代码在交叉点处颜色较深.无论如何都要将交叉点与其他地方的颜色相同？

import matplotlib.pyplot as plt

fig, axs = plt.subplots()
axs.fill([0, 0, 1, 1], [0, 1, 1, 0], alpha=.25, fc='r', ec='none')
axs.fill([0.5, 0.5, 1.5, 1.5], [0.5, 1.5, 1.5, 0.5], alpha=.25, fc='r', ec='none')

Answer 1

正如@unutbu和@Martin Valgur的评论所表明的那样,我认为要走的路要走.对于早期的问题,这个问题可能有点多余,但这里有一个干净的代码片段,应该做你需要的.

策略是首先创建各种形状(矩形)的并集,然后绘制联合.这样你就可以将各种形状"扁平"成一个,所以你在重叠区域没有alpha问题.

import shapely.geometry as sg
import shapely.ops as so
import matplotlib.pyplot as plt

#constructing the first rect as a polygon
r1 = sg.Polygon([(0,0),(0,1),(1,1),(1,0),(0,0)])

#a shortcut for constructing a rectangular polygon
r2 = sg.box(0.5,0.5,1.5,1.5)

#cascaded union can work on a list of shapes
new_shape = so.cascaded_union([r1,r2])

#exterior coordinates split into two arrays, xs and ys
# which is how matplotlib will need for plotting
xs, ys = new_shape.exterior.xy

#plot it
fig, axs = plt.subplots()
axs.fill(xs, ys, alpha=0.5, fc='r', ec='none')
plt.show() #if not interactive