matplotlib savefig() plots different from show()

Question

When I use show() to plot the graphs in X, the graphs looks very good. However when I start to use savefig() to generate large amount of graphs, the savefig() generated graphs ' font, lines, polygons all look smaller than the show() generated graph. My environment is Ubuntu and the backend for show() is Qt4Agg. How can I make the show() plot and the savefig() plot looks consistent?

Answer 1

savefig specifies the DPI for the saved figure (The default is 100 if it's not specified in your .matplotlibrc, have a look at the dpi kwarg to savefig). It doesn't inheret it from the DPI of the original figure.

The DPI affects the relative size of the text and width of the stroke on lines, etc. If you want things to look identical, then pass fig.dpi to fig.savefig.

E.g.

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

Answer 2

You render your matplotlib plots to different devices (e.g., on-screen via Quartz versus to to-file via pdf using different functions (plot versus savefig) whose parameters are nearly the same, yet the default values for those parameters are not the same for both functions.

Put another way, the savefig default parameters are different from the default display parameters.

Aligning them is simple if you do it in the matplotlib config file. The template file is included with the source package, and named matplotlibrc.template. If you did not create one when you installed matplotlib, you can get this template from the matplotlib source, or from the matplotlib website.

Once you have customized this file the way you want, rename it to matplotlibrc (no extension) and save it to the directory .matplotlib (note the leading '.') which should be in your home directory.

The config parameters for saving figures begins at about line 314 in the supplied matplotlibrc.template (first line before this section is: ### SAVING FIGURES).

In particular, you will want to look at these:

savefig.dpi       : 100         # figure dots per inch savefig.facecolor : white       # figure facecolor when saving savefig.edgecolor : white       # figure edgecolor when saving savefig.extension : auto        # what extension to use for savefig('foo'), or 'auto' 

Below these lines are the settings for font type and various image format-specific parameters.

These same parameters for display, i.e., PLT.show(), begin at about line 277 a in the matplotlibrc.template (this section preceded with the line: ### FIGURE):

figure.figsize   : 8, 6           figure.dpi       : 80             figure.facecolor : 0.75        figure.edgecolor : white      

As you can see by comparing the values of these two blocks of parameters, the default settings for the same figure attribute are different for savefig versus display (show).