Closed
Description
Bug report
The cairo backend ignores the alpha value of artists when rendering Collections such as PatchCollection.
Code for reproduction
import matplotlib
matplotlib.use('Cairo')
import matplotlib.pyplot as plt
from matplotlib.collections import PatchCollection
import numpy as np
circles = [plt.Circle((i,i), 1.0) for i in np.arange(10)]
col = PatchCollection(circles, alpha=0.5)
ax = plt.gca()
ax.add_collection(col)
ax.autoscale_view()
plt.savefig('test_cairo_alpha.png')Actual outcome
Expected outcome
Expected output when using the default Qt5Agg backend:
Matplotlib version
- Operating system: Ubuntu 18.04
- Matplotlib version: master @ 4dbbd22
- Matplotlib backend (
print(matplotlib.get_backend())): cairo - Python version: 3.6.6
- Jupyter version (if applicable):
- Other libraries: