python - how to get the data from an plt.imshow()?

Question

I have the following code

import scipy.misc
import matplotlib.pyplot as plt

a = plt.imshow(scipy.misc.lena())

and what I'm hoping to achieve is get the data on lena by accessing a or it's children.

The reason is I'll be accessing the image as plt.gcf() or plt.gca()

Answer 1

a should be a matplotlib.image.AxesImage instance, in which case you can use

a.get_array() 

and

a.set_array(data)

The array is stored as a masked array.

Example

There's an official example available at http://matplotlib.org/examples/animation/dynamic_image.html.

Direct access

You can also use

a._A

to access the array data directly, though I imagine that the getters and setters are the preferred method.

Answer 2

### get image from the plot ###
plt.figure()

...

plt.imshow(image)

# remove white padding
plt.subplots_adjust(left=0, right=1, top=1, bottom=0)
plt.axis('off')
plt.axis('image')

# redraw the canvas
fig = plt.gcf()
fig.canvas.draw()

# convert canvas to image using numpy
img = np.fromstring(fig.canvas.tostring_rgb(), dtype=np.uint8, sep='')
img = img.reshape(fig.canvas.get_width_height()[::-1] + (3,))

# opencv format
img = cv2.cvtColor(img, cv2.COLOR_RGB2BGR)

plt.close()