Getting an RGBA array from a matplotlib image

Question

I was using imshow to plot an array with a custom colormap and boundarynorm. However, this is going to be an automated script and I want to save the image produced

Answer 1

You can use as_rgba_str to get the image data from the image. Here's an example:

import numpy as np
import matplotlib.pyplot as plt

x = np.linspace(0, 2, 1000)
X, Y = np.meshgrid(x, x)
data = np.sin((X-2)**3 + Y**4)

im = plt.imshow(data)

x = im.make_image()
h, w, d = x.as_rgba_str()
n = np.fromstring(d, dtype=np.uint8).reshape(h, w, 4)

plt.figure()
plt.imshow(n[:,:,0], cmap="gray", origin='lower')

plt.show()

The original image:

The R channel from the RGBA data (note all the blue sections are black since these have no red in them):