Save MNIST data as PNG.

mnist_save_png.py

import os
import cv2
import numpy as np

train_image = 'train-images-idx3-ubyte'
train_label = 'train-labels-idx1-ubyte'
test_image = 't10k-images-idx3-ubyte'
test_label = 't10k-labels-idx1-ubyte'

for f in [train_image, train_label, test_image, test_label]:
	os.system('wget --no-check-certificate http://yann.lecun.com/exdb/mnist/%s.gz' % (f,))
	
for f in [train_image, train_label, test_image, test_label]:
	os.system('gunzip %s.gz' % (f,))

for image_f, label_f in [(train_image, train_label), (test_image, test_label)]:
	with open(image_f, 'rb') as f:
		images = f.read()
	with open(label_f, 'rb') as f:
		labels = f.read()
	
	images = [ord(d) for d in images[16:]]
	images = np.array(images, dtype=np.uint8)
	images = images.reshape((-1,28,28))
	
	outdir = image_f + "_folder"
	if not os.path.exists(outdir):
		os.mkdir(outdir)
	for k,image in enumerate(images):
		cv2.imwrite(os.path.join(outdir, '%05d.png' % (k,)), image)
	
	labels = [outdir + '/%05d.png %d' % (k, ord(l)) for k,l in enumerate(labels[8:])]
	with open('%s.txt' % label_f, 'w') as f:
		f.write(os.linesep.join(labels))