Displaying PNG in matplotlib.pyplot framework in python 2.7

Question

I am pulling PNG images from Jupyter Notebooks and manage to display with IPython.display.Image but not with matplotib.pyplot.plt. What am I missing? I use python 2.7.

I am using the following algorithm:

To open the notebook JSON content I do:

import nbformat
notebook_ = nbformat.read(file_notebook, 4)

After retrieving the relevant cell information I pull the png information from it using:

def cell_to_image(cell, out_value_item_number=1):
    if "execution_count" in cell.keys(): # i.e version >=4
        return cell["outputs"][out_value_item_number]['data']['image/png']
    elif "prompt_number" in cell.keys(): # i.e version < 4
        return cell["outputs"][out_value_item_number]['png']
    return None

cell_image = cell_to_image(cell)

The first few characters of cell_image (which is unicode) looks like:

iVBORw0KGgoAAAANSUhEUgAAA64AAAFMCAYAAADLFeHSAAAABHNCSVQICAgIfAhkiAAAAAlwSFlz\n
AAALEgAACxIB0t1+/AAAIABJREFUeJzs3Xd8jef/x/HXyTjZiYQkCGrU3ruR0tr9oq2qGtGo0dbe
\nm5pVlJpFUSMoVb6UoEZ/lCpatWuPUiNEEiMDmef3R75OexonJKUO3s/HI4/mXPd1X/d1f+LRR965
\n7/u6DSaTyYSIiIiIiIiIjbJ70hMQERERERERyYiCq4iIiIiIiNg0BVcRERERERGxaQquIiIiIiIi
\nYtMUXEVERERERMSmKbiKiIiIiIiITVNwFRGRxyIkJIRixYqxfv36+24/e/YsxYoVo3jx4v/yzGxb
\naGgoderUIS4uDoBdu3bRsmVLKlasyCuvvMKgQYOIjo622CcsLIyGDRtSunRp6tSpw8KFC62OW7p0
\naRo2bJju53Lnzh1GjRrFyy+/TNmyZWnRogW//fbbQ835q6++olGjRpQvX5769eszc+ZMkpOTzdtT
\nU1OZNGkSNWrUoHTp0jRp0oTdu3enGyc2NpZOn

I can easily plot in my Jupityer notebook using

from IPython.display import Image   
Image(cell_image)

And now to my question:

How can I manipulate cell_image to be plt.subplot friendly? (Assuming import matplotlib.pyplot as plt). I realise that plt.imshow wouldn't work because this would require an array, which is not my case (which is a string, as far as I understand).

StuckAt7 · Accepted Answer · 2016-09-20 14:57:18Z

2

If you have your image string representation in a variable string_rep, the following code should work.

from io import BytesIO

import matplotlib.image as mpimage
import matplotlib.pyplot as plt

with BytesIO(string_rep.decode('base64')) as byte_rep:
    image = mpimage.imread(byte_rep)

plt.imshow(image)

edited Sep 20, 2016 at 14:57

answered Sep 16, 2016 at 20:23

StuckAt7

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