How to Set Opacity of Background Colour of Graph with Matplotlib

How to set opacity of background colour of graph with Matplotlib

If you just want the entire background for both the figure and the axes to be transparent, you can simply specify transparent=True when saving the figure with fig.savefig.

e.g.:

import matplotlib.pyplot as plt
fig = plt.figure()
plt.plot(range(10))
fig.savefig('temp.png', transparent=True)

If you want more fine-grained control, you can simply set the facecolor and/or alpha values for the figure and axes background patch. (To make a patch completely transparent, we can either set the alpha to 0, or set the facecolor to 'none' (as a string, not the object None!))

e.g.:

import matplotlib.pyplot as plt

fig = plt.figure()

fig.patch.set_facecolor('blue')
fig.patch.set_alpha(0.7)

ax = fig.add_subplot(111)

ax.plot(range(10))

ax.patch.set_facecolor('red')
ax.patch.set_alpha(0.5)

# If we don't specify the edgecolor and facecolor for the figure when
# saving with savefig, it will override the value we set earlier!
fig.savefig('temp.png', facecolor=fig.get_facecolor(), edgecolor='none')

plt.show()

Matplotlib figure facecolor alpha while saving (background color, transparency)

I ran your code on Matplotlib 1.5 and found that it produced the expected output for me. For all happening on upon this in the future I give two concise ways of achieving this below.

A quick note, you definitely don't want to set transparent=True as an option for savefig as this will override the facecolors as you can see in the matplotlib.figure.savefig source.

To actually solve your problem the second link you posted How to set opacity of background colour of graph wit Matplotlib actually solves the problem. The issue with the code snippet in the question is the use of fig.set_facecolor as opposed to fig.patch.set_facecolor

Fix 1:

From the above linked question use the facecolor argument to savefig

import matplotlib.pyplot as plt

fig = plt.figure()
fig.patch.set_facecolor('b') # instead of fig.patch.set_facecolor
fig.patch.set_alpha(0.5)

plt.plot([1,3], [1,3])
plt.tight_layout()
plt.show()
plt.savefig('method1.png', facecolor=fig.get_facecolor())

Fix 2:

You can also specify the savefig facecolor through the rcParams.

import matplotlib.pyplot as plt
import matplotlib as mpl

fig = plt.figure()

col = 'blue'
#specify color of plot when showing in program. 
#fig.set_facecolor(col) also works
fig.patch.set_facecolor(col)
#specify color of background in saved figure
mpl.rcParams['savefig.facecolor'] = col 

#set the alpha for both plot in program and saved image
fig.patch.set_alpha(0.5)
plt.plot([1,3], [1,3])
plt.tight_layout()
plt.show()
plt.savefig('method2.png')

If you you would like your axes to have a background these solution should leave that background (such as produced by seaborn in Erotemic's comment) intact. If you want to be more explicit about it add:

ax.patch.set_color('palegoldenrod') # or whatever color you like
ax.patch.set_alpha(.7)

The axis patch alpha will transfer to savefig without extra effort.

Note that in both cases I used plt.tight_layout() to eliminate useless extra space in the saved figure. You can read more on that in the matplotlib documentation.

How to set transparency and background colour for a pie chart matplotlib

There are two similar ways: the basic idea is to define the wedge properties
using wedgeprops. On a side note, I would rather use lightgrey background as it looks much better than grey which is a bit dark.

First:

df['C'].value_counts().plot(kind = 'pie',wedgeprops={'alpha':0.5})
fig.set_facecolor('lightgrey')

Second: using plt.pie

plt.pie(df['C'].value_counts(), wedgeprops={'alpha':0.5})
fig.set_facecolor('lightgrey')

How to directly set alpha channel value for matplotlib figure background colour

Looks like a bug to me. I've submitted a PR to fix it. If you're able, it'd be really valuable if you could try it out: https://github.com/matplotlib/matplotlib/pull/1868

HTH

How to change the color of the background in a Networkx plot?

You can change the background color with ax.set_facecolor.
If you don't created an ax, you could use plt.gca().set_facecolor.
If you also want to remove the black border, use ax.axis('off').
Note that the bg_color= is ignored in nx.draw_networkx.

import networkx as nx
import matplotlib.pyplot as plt

fig, ax = plt.subplots()
nx.draw_networkx(nx.dodecahedral_graph(),
                 with_labels=False, node_shape='*', node_size=300, node_color='gold',
                 edge_color='crimson', width=5)
ax.set_facecolor('deepskyblue')
ax.axis('off')
fig.set_facecolor('deepskyblue')
plt.show()

Adjusting Text background transparency

The alpha passed to plt.text() will change the transparency of the text font. To change the background you have to change the alpha using Text.set_bbox():

t = plt.text(0.5, 0.5, 'text', transform=ax.transAxes, fontsize=30)
t.set_bbox(dict(facecolor='red', alpha=0.5, edgecolor='red'))
#changed first dict arg from "color='red'" to "facecolor='red'" to work on python 3.6

To remove the border of the text box, as suggested in the comment of @halt9k, you can use .set_bbox(dict(facecolor='white', alpha=0.5, linewidth=0)).

Export matplotlib with transparent background

This works for me:

import matplotlib.pyplot as plt
from PIL import Image, ImageFont, ImageDraw

path = '...'

SomeCanvas1 = Image.new('RGB', (750, 750), '#36454F')

fig, ax = plt.subplots(figsize=(6, 6))
wedgeprops = {'width':0.3, 'edgecolor':'white', 'linewidth':2}
ax.pie([1-0.33,0.33], wedgeprops=wedgeprops, startangle=90, colors=['#BABABA', '#0087AE'])
plt.text(0, 0, '33%', ha='center', va='center', fontsize=42)
fig.savefig(path+'donut1.png', transparent=True)

imgDonut = Image.open(path+'donut1.png')
w,h = imgDonut.size

SomeCanvas1.paste(imgDonut, (int(0.5*(750-w)),int(0.5*(750-h))))
SomeCanvas1.save(path+'test1.png')
fig.patch.set_alpha(0)

The output is (I have black background --> this is screenshot from JupyterLab):

This is your file ...donut1.png (transparent background, my viewer has white background --> this is the actual image file):

----edit---

Managed to get it transparent!

import matplotlib.pyplot as plt
from PIL import Image, ImageFont, ImageDraw

path = '...'

SomeCanvas1 = Image.new('RGB', (750, 750), '#36454F')

fig, ax = plt.subplots(figsize=(6, 6))
wedgeprops = {'width':0.3, 'edgecolor':'white', 'linewidth':2}
ax.pie([1-0.33,0.33], wedgeprops=wedgeprops, startangle=90, colors=['#BABABA', '#0087AE'])
plt.text(0, 0, '33%', ha='center', va='center', fontsize=42)
fig.savefig(path+'donut1.png', transparent=True)
fig.patch.set_alpha(0)

SomeCanvas1.save(path+'test1.png')

foreground = path+'donut1.png'
imgfore = Image.open(foreground, 'r')
background = path+'test1.png'
imgback = Image.open(background, 'r')

merged = Image.new('RGBA', (w,h), (0, 0, 0, 0))
merged.paste(imgback, (0,0))
merged.paste(imgfore, (0,0), mask=imgfore)
merged.save((path+"merged.png"), format="png")

In this case you will produce 3 image files. This is the merged file:

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