[Matplotlib-users] problem with png image

[Petro <x....@gm...>]

Hi list.
I generate some png images using matplotlib, and get very different
results depending on figuresize
__________________________________________________________________
  from pylab import figure, plot
  import pylab as plt 
  import numpy as np
  figure()
  plt.subplot(2,1,1)
  plot(np.random.rand(10),'o')
  plt.subplot(2,1,2)
  plot(np.random.rand(10),'o')
  pic_name='fit_rates1.png'
  path_name='/home/petro/tmp/'
  plt.savefig(path_name + pic_name) 
__________________________________________________________________

the code above generates the following image:
https://lh3.googleusercontent.com/-107Ducz_CA0/UDShKMtejtI/AAAAAAAACls/YOeahS3tQA8/s400/fit_rates1.png

now if I increase a figure  size parameter:
__________________________________________________________________
  from pylab import figure, plot
  import pylab as plt 
  import numpy as np
  plt.ioff()
  from matplotlib import rcParams 
  golden_mean = (np.sqrt(5)-1.0)/2.0    # Aesthetic ratio
  fig_width = 5.6  # width in inches
  fig_height = fig_width*golden_mean    # height in inches
  rcParams['figure.figsize']=fig_width, fig_height*3
  figure()
  plt.subplot(2,1,1)
  plot(np.random.rand(10),'o')
  plt.subplot(2,1,2)
  plot(np.random.rand(10),'o')
  pic_name='fit_rates2.png'
  path_name='/home/petro/tmp/'
  plt.savefig(path_name + pic_name) 
  
__________________________________________________________________
the result looks strange like this:
https://lh5.googleusercontent.com/-4GRQxuRFvh4/UDSiRrNy59I/AAAAAAAACmA/Kho3prHFpUU/s640/fit_rates2.png
Has anyone experienced behaviour like this?
Thanks.
Petro