Display MNIST image using matplotlib

You are casting an array of floats (as described in the docs) to uint8, which truncates them to 0, if they are not 1.0. You should either round them or use them as floats or multiply with 255.

I am not sure, why you don't see the white background, but i would suggest to use a well defined gray scale anyway.

Here is the complete code for showing image using matplotlib

from matplotlib import pyplot as plt
import numpy as np
from tensorflow.examples.tutorials.mnist import input_data

mnist = input_data.read_data_sets('MNIST_data', one_hot = True)
first_image = mnist.test.images[0]
first_image = np.array(first_image, dtype='float')
pixels = first_image.reshape((28, 28))
plt.imshow(pixels, cmap='gray')
plt.show()

The following code shows example images displayed from the MNIST digit database used for training neural networks. It uses a variety of pieces of code from around stackflow and avoids pil.

# Tested with Python 3.5.2 with tensorflow and matplotlib installed.
from matplotlib import pyplot as plt
import numpy as np
from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets('MNIST_data', one_hot = True)
def gen_image(arr):
    two_d = (np.reshape(arr, (28, 28)) * 255).astype(np.uint8)
    plt.imshow(two_d, interpolation='nearest')
    return plt

# Get a batch of two random images and show in a pop-up window.
batch_xs, batch_ys = mnist.test.next_batch(2)
gen_image(batch_xs[0]).show()
gen_image(batch_xs[1]).show()

The definition of mnist is at: https://github.com/tensorflow/tensorflow/blob/master/tensorflow/contrib/learn/python/learn/datasets/mnist.py

The tensorflow neural network that led me to the need to display the MNINST images is at: https://github.com/tensorflow/tensorflow/blob/r1.2/tensorflow/examples/tutorials/mnist/mnist_deep.py

Since I have only been programming Python for two hours, I might have made some newby errors. Please feel free to correct.