DOC: better document rcParams in savefig.* grouping

Feature request

Feature summary

The FAQ https://matplotlib.org/faq/howto_faq.html describes a way to make the figure patch transparent, see "Save transparent figures". It would be great to have an option for the matplotlibrc file to always make the figure patch transparent.

Code

As described in the FAQ, the following code makes the figure patch transparent.

from matplotlib import pyplot as plt
fig = plt.figure()
fig.patch.set_alpha(0.0) # set this via rcParams?

I am aware of the rcParams option "savefig.transparent" which makes the figure patch and the axis patch transparent. I only want the figure patch to be transparent, because this looks very nice on slides with a gradient on the background.

Matplotlib version

Operating System: MacOS
Matplotlib Version: 2.0.2
Python Version: 2.7.10

Related issue: #2384

I am happy to work on a PR if this has a chance of being accepted.

The facecolor can be an RGBA value so setting

mpl.rcParams['figure.facecolor'] = (0, 0, 0, 0)

should do what you want?

Hi Thomas,

I tried this, but full RGBA values are not supported in matplotlibrc. When I set this

figure.facecolor  : (0, 0, 0, 0)

I get this error:

/Users/hdembins/Library/Python/2.7/lib/python/site-packages/matplotlib/__init__.py:1120: UserWarning: Bad val "(0, 0, 0, 0)" on line #26
    "figure.facecolor  : (0, 0, 0, 0)
"
    in file "/Users/hdembins/.matplotlib/matplotlibrc"
    Key figure.facecolor: (0, 0, 0, 0) does not look like a color arg
Color tuples must be length 3
  (val, error_details, msg))

So perhaps the more general solution is to allow full RGBA colors in matplotlibrc.

Update: It also turns out the following code does not work as expected:

import matplotlib.pyplot as plt
from matplotlib import rcParams

rcParams["figure.facecolor"] = (0, 0, 0, 0)

plt.figure()
plt.plot([], [])
plt.savefig("testme.png")

Opening testme.png shows a white background, not a transparent background for the figure patch. I think that is a bug. The following works:

import matplotlib.pyplot as plt

fig = plt.figure()
fig.patch.set_alpha(0)
plt.plot([], [])
plt.savefig("testme2.png")

See the result:

To me it looks like the figure is transparent but the axis is not. That is what I would expect when you set the figure transparent and the axes facecolor has its default value which is white.
I would expect

rcParams["axes.facecolor"] = (0, 0, 0, 0)

to do the trick

Hi Jens, yes, I had the same expectation from my naive point of view.

And just to clarify: the attached picture (testme2.png) is the desired outcome that I want.

Hi Jens, sorry, I was not reading closely enough what you wrote.

rcParams["axes.facecolor"] = (0, 0, 0, 0)

does not work either, it produces just a white figure background and a white axes background. Also, I don't want the axes background to be transparent, only the figure background.

Ok I assumed that the attached image was the broken behaviour

The right rcparam to set is savefig.facecolor.
Right now you can work around the lack of support for 4-tuples using #00000000 (i.e. #rrggbbaa format, introduced in #6382); #9038 adds support for 4-tuples.

@anntzer

@anntzer Thanks for the related PR :). I take whatever works, but I think that setting savefig.facecolor to get the desired result is not intuitive.

Hmm, we change savefig.dpi to default to 'figure', I thought we had done the same with the rest of them.

There is also 'savefig.transparent' which I think does the same thing in a more direct way (which I had forgotten about apparently).

@tacaswell

@tacaswell I read about savefig.transparent but it does not what I need. It makes the figure background and the axis background transparent. I only want the figure background transparent, but keep the axes background white, i.e. what is shown in the screenshot above.

@anntzer

@anntzer I can confirm that this code

import matplotlib.pyplot as plt
from matplotlib import rcParams

rcParams["savefig.facecolor"] = (0, 0, 0, 0)

fig = plt.figure()
plt.plot([], [])
plt.savefig("testme2.png")

produces exactly what I want. Thanks! 😄

Following your advice as I understood it, I tried to add this line to my matplotlibrc:

savefig.facecolor: #00000000

But I then get this error:

/Users/hdembins/Library/Python/2.7/lib/python/site-packages/matplotlib/__init__.py:1120: UserWarning: Bad val """ on line #31
    "savefig.facecolor: "#00000000""
    in file "/Users/hdembins/.matplotlib/matplotlibrc"
    Key savefig.facecolor: " does not look like a color arg
  (val, error_details, msg))

Okay, looking into the relevant code myself helps ;)
It works with the current matplotlib 2.0.2, if I put this line into matplotlibrc

savefig.facecolor: 00000000

Note that one has to omit the #-prefix, which is not intuitive. I think the color format in matplotlibrc should be identical to the one in Python.

Ok, nevermind, the # in matplotlibrc starts a comment, that's why the color cannot be prefixed like this. I guess it is not worth the effort to make an exception in the parser for this sort of thing.

This is fantastic. Thanks everyone!

Navigation Menu

Repository navigation

DOC: better document rcParams in savefig.* grouping #9030

Feature request

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

DOC: better document rcParams in savefig.* grouping #9030

Description

Feature request

Activity

HDembinski commented on Aug 14, 2017

HDembinski commented on Aug 14, 2017

tacaswell commented on Aug 14, 2017

HDembinski commented on Aug 15, 2017

HDembinski commented on Aug 15, 2017

HDembinski commented on Aug 15, 2017

jenshnielsen commented on Aug 15, 2017

HDembinski commented on Aug 15, 2017

HDembinski commented on Aug 15, 2017

jenshnielsen commented on Aug 15, 2017

anntzer commented on Aug 15, 2017

HDembinski commented on Aug 15, 2017

tacaswell commented on Aug 15, 2017

HDembinski commented on Aug 16, 2017

HDembinski commented on Aug 16, 2017

HDembinski commented on Aug 16, 2017

HDembinski commented on Aug 16, 2017

HDembinski commented on Aug 23, 2017

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions