how to save a pylab figure into in-memory file which can be read into PIL image?

Question

The following is my first shot which never works:

import cStringIO import pylab from PIL import Image pylab.figure() pylab.plot([1,2]) pylab.title("test") buffer = cStringIO.StringIO() pylab.savefig(buffer, format='png') im = Image.open(buffer.read()) buffer.close() 

the error says,

Traceback (most recent call last):   File "try.py", line 10, in <module>     im = Image.open(buffer.read())   File "/awesomepath/python2.7/site-packages/PIL/Image.py", line 1952, in open     fp = __builtin__.open(fp, "rb") 

any ideas? I don't want the solution to involve extra packages.

Answer 1

Remember to call buf.seek(0) so Image.open(buf) starts reading from the beginning of the buf:

import io from PIL import Image import matplotlib.pyplot as plt  plt.figure() plt.plot([1, 2]) plt.title("test") buf = io.BytesIO() plt.savefig(buf, format='png') buf.seek(0) im = Image.open(buf) im.show() buf.close() 

Answer 2

I like having it encapsulated in a function:

def fig2img(fig):     """Convert a Matplotlib figure to a PIL Image and return it"""     import io     buf = io.BytesIO()     fig.savefig(buf)     buf.seek(0)     img = Image.open(buf)     return img 

Then I can call it easily this way:

import numpy as np import matplotlib.pyplot as plt from PIL import Image  x = np.arange(-3,3) plt.plot(x) fig = plt.gcf()  img = fig2img(fig) img.show()