Pyplot animation not updating continuously

Question

I'm trying to display the frames captured by a CCD camera in real-time using pyplot animation. I wrote a short python script just to test this out, and while it works, it does so erratically. It will quickly update a dozen or so animation frames, then pause for a second, then update again, then pause again, and so on. I'd like to just have it update the plot continuously and smoothly, but I'm not sure where I'm going wrong.

I know it isn't the part where it makes a call to the camera's frame buffer; I tested out just calling that in a loop and it never slowed down, so I think it's somewhere in the actual processing of the animation frames.

My code is below:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
import Pixis100
import time

# First set up the figure, the axis, and the plot element we want to animate
fig = plt.figure()
ax = fig.add_subplot(111)    

# Create ccd object
ccd = Pixis100.device()
ccd.snapshot()
ccd.focusStart()
# focusStart() tells the camera to start putting captured frames into the buffer

line, = ax.plot(ccd.getFrame()[:,2:].sum(axis=0)[::-1],'b-')
# getFrame() makes a call to the CCD frame buffer and retrieves the most recent frame

# animation function
def update(data):    
    line.set_ydata(data)
    return line,

def data_gen():
    while True: yield ccd.getFrame()[:,2:].sum(axis=0)[::-1]

# call the animator
anim = animation.FuncAnimation(fig, update, data_gen,interval=10,blit=True)

plt.show()
ccd.focusStop()
# focusStop() just tells the camera to stop capturing frames

For reference, ccd.getFrame()[:,2:].sum(axis=0)[::-1] returns a 1x1338 array of integers. I wouldn't think this would be too much for the animation to handle at one time.

does it run better if you increase the interval? I would point out 10ms is 100fps. I suspect the culprit here is the gui-frame work you are using not being able to re-draw the canvas at that rate. It as also not clear if you have a question or are just whining. — tacaswell
– tacaswell, Commented Jul 13, 2013 at 15:43
Changing the interval doesn't help. My question is what would cause the plot to update erratically, as I described; if it's an issue of pyplot and a different plotting library would work better, or if there's something within pyplot I can do to fix this issue. — camronm21
– camronm21, Commented Jul 14, 2013 at 17:37

piem · Accepted Answer · 2018-10-17 15:06:34Z

1

The problem is not in animation, the following works just fine:

import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation

import time

# First set up the figure, the axis, and the plot element we want to animate
fig = plt.figure()
ax = fig.add_subplot(111)    
ax.set_xlim([0, 2 *np.pi])
ax.set_ylim([-1, 1])

th = np.linspace(0, 2 * np.pi, 1000)

line, = ax.plot([],[],'b-', animated=True)
line.set_xdata(th)
# getFrame() makes a call to the CCD frame buffer and retrieves the most recent frame

# animation function
def update(data):    
    line.set_ydata(data)

    return line,

def data_gen():
    t = 0
    while True:
        t +=1
        yield np.sin(th + t * np.pi/100)

# call the animator
anim = animation.FuncAnimation(fig, update, data_gen, interval=10, blit=True)
plt.show()

The choppyness may come from either your frame grabber, the computation your are doing on it, or issues with the gui getting enough time on the main thread to re-draw. See time.sleep() required to keep QThread responsive?

edited Oct 17, 2018 at 15:06

piem

3902 silver badges11 bronze badges

answered Jul 14, 2013 at 19:46

tacaswell

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1 Comment

Sazzad Hissain Khan Feb 4 at 6:34

The graph not animating on my Jupyter notbook. Anything need to configure?

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