How to make savefig() save image for ‘maximized’ window instead of default size

There are two major options in matplotlib (pylab) to control the image size:

1. You can set the size of the resulting image in inches
2. You can define the DPI (dots per inch) for output file (basically, it is a resolution)

Normally, you would like to do both, because this way you will have full control over the resulting image size in pixels. For example, if you want to render exactly 800×600 image, you can use DPI=100, and set the size as 8 x 6 in inches:

import matplotlib.pyplot as plt
# plot whatever you need...
# now, before saving to file:
figure = plt.gcf() # get current figure
figure.set_size_inches(8, 6)
# when saving, specify the DPI
plt.savefig("myplot.png", dpi = 100)

One can use any DPI. In fact, you might want to play with various DPI and size values to get the result you like the most. Beware, however, that using very small DPI is not a good idea, because matplotlib may not find a good font to render legend and other text. For example, you cannot set the DPI=1, because there are no fonts with characters rendered with 1 pixel 🙂

From other comments I understood that other issue you have is proper text rendering. For this, you can also change the font size. For example, you may use 6 pixels per character, instead of 12 pixels per character used by default (effectively, making all text twice smaller).

import matplotlib
#...
matplotlib.rc('font', size=6)

Finally, some references to the original documentation:
http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.savefig, http://matplotlib.sourceforge.net/api/pyplot_api.html#matplotlib.pyplot.gcf, http://matplotlib.sourceforge.net/api/figure_api.html#matplotlib.figure.Figure.set_size_inches, http://matplotlib.sourceforge.net/users/customizing.html#dynamic-rc-settings

P.S. Sorry, I didn’t use pylab, but as far as I’m aware, all the code above will work same way in pylab – just replace plt in my code with the pylab (or whatever name you assigned when importing pylab). Same for matplotlib – use pylab instead.