How to Save Figure as PNG Byte Array With Decimal Formatting

I have some data I'm visualizing with a MatPlotLib figure. I want to be able to convert the figure into a byte array that is formatted with PNG decimal values.
https://www.w3.org/TR/PNG-Structure.html

fig = plt.figure(figsize=(16,16))
ax = fig.add_subplot(projection='3d')
ax.voxels(space, facecolors = rgb_input)
plt.axis('off')
fig.patch.set_alpha(0.25)
ax.patch.set_alpha(0.25)

I know how to save it as a PNG and convert that into a byte array, but I want to be able to make the byte array directly.

I've tried using this to get the byte array directly, but it doesn't return PNG decimal values:

buf = io.BytesIO()
plt.savefig(buf, format = 'png')
buf.seek(0)
data = buf.read()

EDIT: Upon further research, I've found that the data value is formatted as an ASCII byte array. Is there a way to convert it into a decimal byte array?

PNG images are binary files usually represented in ASCII or hexadecimal, to convert the byte array into a decimal representation, you can simply do that with Python's built-in functions.

import io
import matplotlib.pyplot as plt
import numpy as np

space = np.random.rand(5,5,5) > 0.5
rgb_input = np.random.rand(5,5,5,3)

fig = plt.figure(figsize=(16,16))
ax = fig.add_subplot(projection='3d')
ax.voxels(space, facecolors = rgb_input)
plt.axis('off')
fig.patch.set_alpha(0.25)
ax.patch.set_alpha(0.25)

buf = io.BytesIO()
plt.savefig(buf, format = 'png')
buf.seek(0)
data = buf.read()

decimal_values = [byte for byte in data]
print(decimal_values)