python - 我添加到图表中的补丁在 alpha=1 时不是不透明的。为什么？

Question

我想在图形上添加一个矩形。通过我找到的所有文档，默认情况下矩形应该是不透明的，透明度由 alpha 参数控制。但是，即使 alpha = 1，我也无法让矩形显示为不透明。我是做错了什么，还是我需要了解有关图形与补丁交互方式的其他信息？

这是一个玩具示例:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
from pylab import *

x = np.arange(10)
y = x
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(x, y)

rect = patches.Rectangle( ( 2,3 ), 2, 2, alpha = 1, ec = "gray", fc = "CornflowerBlue", visible = True)
ax.add_patch(rect)

plt.show()

Answer 1

来自documentation :

Within an axes, the order that the various lines, markers, text, collections, etc appear is determined by the matplotlib.artist.Artist.set_zorder() property. The default order is patches, lines, text, with collections of lines and collections of patches appearing at the same level as regular lines and patches, respectively.

因此默认情况下，补丁将绘制在线条下方。您可以通过指定矩形的 zorder 来更改顺序:

# note alpha is None and visible is True by default
rect = patches.Rectangle((2, 3), 2, 2, ec="gray", fc="CornflowerBlue", zorder=10)

您可以通过将 ax.plot(x, y) 更改为 lines = ax.plot(x, y) 和添加一行新代码:print lines[0].zorder。当我这样做时，该行的 zorder 为 2。因此，矩形将需要一个 zorder > 2 来遮盖该行。