Use a PNG file as a watermark
Out:
loading /mnt/c/Users/chold/Dropbox/github/forks/python/viz/matplotlib/lib/matplotlib/mpl-data/sample_data/logo2.png
from __future__ import print_function
import numpy as np
import matplotlib.cbook as cbook
import matplotlib.image as image
import matplotlib.pyplot as plt
# Fixing random state for reproducibility
np.random.seed(19680801)
datafile = cbook.get_sample_data('logo2.png', asfileobj=False)
print('loading %s' % datafile)
im = image.imread(datafile)
im[:, :, -1] = 0.5 # set the alpha channel
fig, ax = plt.subplots()
ax.plot(np.random.rand(20), '-o', ms=20, lw=2, alpha=0.7, mfc='orange')
ax.grid()
fig.figimage(im, 10, 10, zorder=3)
plt.show()