does getting image from same cell work?

I have tried to get an image of the canvas from the same cell as described in the documentation. I tried the following code:

from ipycanvas import Canvas
import numpy as np

canvas = Canvas(width=200, height=200, sync_image_data=True)
display(canvas)

def get_array(*args, **kwargs):
    print("here")
    arr = canvas.get_image_data()
    print(arr)
    np.save("whatever.txt", arr)
    # Do something with arr

# Listen to changes on the ``image_data`` trait and call ``get_array`` when it changes.
canvas.observe(get_array, 'image_data')

canvas.stroke_line(50, 10, 150, 10)

Unfortunately nothing happens (except the canvas being drawn). Can you confirm that this works for you?

PS: What I am trying to achieve is creating a gif/video from an animation, which is still an open issue as far as I have seen. But I try it “by hand”.

[Weihnachtshase]

This was actually the problem 😃

This code works now for me:

from ipycanvas import Canvas, hold_canvas
from threading import Thread
import numpy as np
import time


class Test:
    
    def __init__(self):
        self.first = True
        self.images = []
        self.canvas = None
        
    def get_array(self, *args, **kwargs):
        arr = self.canvas.get_image_data()
        self.images.append(arr)
        
    def render(self, x):
        if self.first:
            self.canvas.observe(self.get_array, 'image_data')
            self.first = False
        self.canvas.stroke_line(50, 10+(x*5), 150, 10+(x*5))
        
class MyThread(Thread):
    
    def __init__(self, test):
        super(MyThread, self).__init__()
        self.test = test
    
    def run(self):
        for i in range(10):
            self.test.render(i)
            time.sleep(1)
        

test = Test()
canvas = Canvas(width=200, height=200, sync_image_data=True)
display(canvas)
test.canvas = canvas
MyThread(test).start()

Hope that somehow helps you in the future with your GIF animation creation.

[martinRenou]

This is huge ahah. I haven’t thought of threading when trying the first time.

Thanks a lot for trying! This will definitely help. We would need to think of a way to expose this as a nice and friendly user-API.