Updating image of the widget is slow

[hadim]

I am trying to create a 3D-5D viewer to display 2D images with some sliders to navigate along other dimensions such as time, channel and z.

To update the image I just set the image attribute of the widget to the new image:

if not self.image_widget:
    self.image_widget = itkwidgets.view(self.current_image, ui_collapsed=False, annotations=True,
                                        interpolation=False, cmap='Viridis (matplotlib)', mode='v',
                                        shadow=True, slicing_planes=False, gradient_opacity=0.22)
else:
    self.image_widget.image = self.current_image

It works well but the image update is slow when moving the sliders. The same issue happens with a low-resolution image.

Here is a binder that reproduces the issue: https://mybinder.org/v2/gh/hadim/binder-sandbox/master?urlpath=lab/tree/notebooks/Image%20Viewer.ipynb

[hadim]

xref: https://github.com/jupyter-widgets/ipywidgets/issues/2081

[thewtex]

Here is a binder that reproduces the issue: https://mybinder.org/v2/gh/hadim/binder-sandbox/master?urlpath=lab/tree/notebooks/Image%20Viewer.ipynb

Very nice!

I am trying to create a 3D-5D viewer to display 2D images with some sliders to navigate along other dimensions such as time, channel and z.

To get the behavior you want, we will likely need true 4D support, discussed in #74. We will need to buffer enough data client side time-wise and transfer it into WebGL buffers for the transitions to be fast.

[thewtex]

In 0.27.2, data transmission rates are ~20x faster, so it may be practical without dedicated time support.