How to invert pixel numbers of MNIST data set

[scidam]

I suspect you've used a dataset which is similar to this one.

As far as I understand, pixel inversion is transformation when black colors become white and vice verse?! If so, the following code can help you:

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
data=pd.read_csv("https://raw.githubusercontent.com/sjwhitworth/golearn/master/examples/datasets/mnist_train.csv")
data.values[:, 1:] = np.abs(data.values[:, 1:] - 255)  # color inversion
x=data.values[-1, 1:]  # plot latest row in the dataset
plt.imshow(x.reshape(28, 28), cmap='gray')
plt.show()