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Hello world example

In this example we demonstrate the very basics of the RemoteFrameBuffer class.

import numpy as np
import jupyter_rfb

We start by implementing get_frame() to produce an image.

class HelloWorld1(jupyter_rfb.RemoteFrameBuffer):

    def get_frame(self):
        a = np.zeros((100, 100, 3), np.uint8)
        a[20:-20,20:-20,1] = 255
        return a

w = HelloWorld1()
w

snapshot

Let’s make it a bit more advanced. By keeping track of the widget size, we can provide an array with matching shape. We also take pixel_ratio into account, in case this is a hidpi display, or when the user has used the browser’s zoom.

class HelloWorld2(jupyter_rfb.RemoteFrameBuffer):

    def handle_event(self, event):
        if event["event_type"] == "resize":
            self._size = event
            # self.print(event)  # uncomment to display the event

    def get_frame(self):
        w, h, r = self._size["width"], self._size["height"], self._size["pixel_ratio"]
        physical_size = int(h*r), int(w*r)
        a = np.zeros((physical_size[0], physical_size[1], 3), np.uint8)
        margin = int(20 * r)
        a[margin:-margin,margin:-margin,1] = 255
        return a

w = HelloWorld2()
w

snapshot

If this is a live session, try resizing the widget to see how it adjusts.