I’m working on some computer vision algorithm and I’d like to show how a numpy array changes in each step.
What works now is that if I have a simple imshow( array ) at the end of my code, the window displays and shows the final image.
However what I’d like to do is to update and display the imshow window as the image changes in each iteration.
So for example I’d like to do:
import numpy as np
import matplotlib.pyplot as plt
import time
array = np.zeros( (100, 100), np.uint8 )
for i in xrange( 0, 100 ):
for j in xrange( 0, 50 ):
array[j, i] = 1
#_show_updated_window_briefly_
plt.imshow( array )
time.sleep(0.1)
The problem is that this way, the Matplotlib window doesn’t get activated, only once the whole computation is finished.
I’ve tried both native matplotlib and pyplot, but the results are the same. For plotting commands I found an .ion() switch, but here it doesn’t seem to work.
Q1. What is the best way to continuously display updates to a numpy array (actually a uint8 greyscale image)?
Q2. Is it possible to do this with an animation function, like in the dynamic image example? I’d like to call a function inside a loop, thus I don’t know how to achieve this with an animation function.
Depending on the backend, you may be able to use
f = plt.figure()
f.canvas.flush_events()
Also, I would suggest to clear the image each time you go through the loop, otherwise you’ll end up with a huge number of images on top of each other.
Best,
-Michiel.
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From: zsero <zsolt.ero@…287…> To:matplotlib-users@lists.sourceforge.net Sent: Thursday, July 25, 2013 12:05 AM Subject: [Matplotlib-users] How to update matplotlib’s imshow() window interactively?
I’m working on some computer vision algorithm and I’d like to show how a numpy array changes in each step.
What works now is that if I have a simple imshow( array ) at the end of my code, the window displays and shows the final image.
However what I’d like to do is to update and display the imshow window as the image changes in each iteration.
So for example I’d like to do:
import numpy as np
import matplotlib.pyplot as plt
import time
array = np.zeros( (100, 100), np.uint8 )
for i in xrange( 0, 100 ):
for j in xrange( 0, 50 ):
array[j, i] = 1
#_show_updated_window_briefly_
plt.imshow( array )
time.sleep(0.1)
The problem is that this way, the Matplotlib window doesn’t get activated, only once the whole computation is finished.
I’ve tried both native matplotlib and pyplot, but the results are the same. For plotting commands I found an .ion() switch, but here it doesn’t seem to work.
Q1. What is the best way to continuously display updates to a numpy array (actually a uint8 greyscale image)?
Q2. Is it possible to do this with an animation function, like in the dynamic image example? I’d like to call a function inside a loop, thus I don’t know how to achieve this with an animation function.
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