[FIXED] Change background transparency of AnchoredText in Matplotlib

Issue

I'm trying to use an AnchoredText to print some information on an axis in Matplotlib, but I would like to have its background semitransparent (say alpha=0.5).

My initial guess was:

info_box = AnchoredText('test', loc='upper left', prop=dict(size=8, alpha=0.5), frameon=True,
            bbox_to_anchor=(0., 1.), bbox_transform=axis.transAxes)

axis.add_artist(info_box)

But in this way the text was set 50% transparent, not the background.

Looking around I found that this is the expected behaviour and I have to make the bbox partially transparent, but I could not find how to do this on an AnchoredText object.

Do you have any suggestions?

Solution

You can set the alpha on the object's patch. I agree this is not obvious from the documentation.

import matplotlib.pyplot as plt
from matplotlib.offsetbox import AnchoredText

fig, ax = plt.subplots()
ax.plot([1, 0])
info_box = AnchoredText('test', loc='upper left', prop=dict(size=8), frameon=True,
                        bbox_to_anchor=(0., 1.), bbox_transform=ax.transAxes)
info_box.patch.set_alpha(0.5)

ax.add_artist(info_box)
plt.show()

Answered By - RuthC